Integrating III-V, Si, and polymer waveguides for optical interconnects: RAPIDO

We present a vision for the hybrid integration of advanced transceivers at 1.3 μm wavelength, and the progress done towards this vision in the EU-funded RAPIDO project. The final goal of the project is to make five demonstrators that show the feasibility of the proposed concepts to make optical interconnects and packet-switched optical networks that are scalable to Pb/s systems in data centers and high performance computing. Simplest transceivers are to be made by combining directly modulated InP VCSELs with 12 μm SOI multiplexers to launch, for example, 200 Gbps data into a single polymer waveguide with 4 channels to connect processors on a single line card. For more advanced transceivers we develop novel dilute nitride amplifiers and modulators that are expected to be more power-efficient and temperatureinsensitive than InP devices. These edge-emitting III-V chips are flip-chip bonded on 3 μm SOI chips that also have polarization and temperature independent multiplexers and low-loss coupling to the 12 μm SOI interposers, enabling to launch up to 640 Gbps data into a standard single mode (SM) fiber. In this paper we present a number of experimental results, including low-loss multiplexers on SOI, zero-birefringence Si waveguides, micron-scale mirrors and bends with 0.1 dB loss, direct modulation of VCSELs up to 40 Gbps, ±0.25μm length control for dilute nitride SOA, strong band edge shifts in dilute nitride EAMs and SM polymer waveguides with 0.4 dB/cm loss.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Optoelectronics Research Centre, Research group: Semiconductor Technology and Applications, VTT Technical Research Centre of Finland, IBM Research, Vertilas GmbH, Scuola Superiore sant'Anna, Tyndall National Institute at National University of Ireland, Cork, Modulight Inc.
Contributors: Aalto, T., Harjanne, M., Offrein, B. J., Caër, C., Neumeyr, C., Malacarne, A., Guina, M., Sheehan, R. N., Peters, F. H., Melanen, P.
Publication date: 2016

Host publication information

Title of host publication: Optical Interconnects XVI
Publisher: SPIE
Article number: 97530D
ISBN (Print): 9781628419887

Publication series

Name: Proceedings of SPIE
Volume: 9753
ISSN (Print): 0277-786X
ISSN (Electronic): 1996-756X
ASJC Scopus subject areas: Applied Mathematics, Computer Science Applications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Keywords: electro absorption modulator, hybrid integration, optical interconnect, optical interposer, optoelectronics, polymer photonics, semiconductor optical amplifier, Silicon photonics, VCSEL, wavelength multiplexers

Bibliographical note

EXT="Melanen, Petri"

Source: Scopus
Source ID: 84975114015

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Frequency Comb Generation in a Continuous-Wave Pumped Second-Order Nonlinear Waveguide Resonator

Optical frequency comb generation has been experimentally studied using an integrated system based on a lithium niobate waveguide resonator featuring a strong quadratic nonlinearity. Our theoretical model shows good agreement with the experimental results.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Physics, Paderborn University, University of Helsinki, VTT Technical Research Centre of Finland
Contributors: Abdallah, Z., Stefszky, M., Ulvila, V., Silberhorn, C., Vainio, M.
Publication date: 1 May 2019

Host publication information

Title of host publication: 2019 Conference on Lasers and Electro-Optics, CLEO 2019 - Proceedings
Publisher: IEEE
ISBN (Electronic): 9781943580576
ASJC Scopus subject areas: Spectroscopy, Industrial and Manufacturing Engineering, Safety, Risk, Reliability and Quality, Management, Monitoring, Policy and Law, Electronic, Optical and Magnetic Materials, Radiology Nuclear Medicine and imaging, Instrumentation, Atomic and Molecular Physics, and Optics
Source: Scopus
Source ID: 85069196416

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Adaptive multiresolution method for MAP reconstruction in electron tomography

3D image reconstruction with electron tomography holds problems due to the severely limited range of projection angles and low signal to noise ratio of the acquired projection images. The maximum a posteriori (MAP) reconstruction methods have been successful in compensating for the missing information and suppressing noise with their intrinsic regularization techniques. There are two major problems in MAP reconstruction methods: (1) selection of the regularization parameter that controls the balance between the data fidelity and the prior information, and (2) long computation time. One aim of this study is to provide an adaptive solution to the regularization parameter selection problem without having additional knowledge about the imaging environment and the sample. The other aim is to realize the reconstruction using sequences of resolution levels to shorten the computation time. The reconstructions were analyzed in terms of accuracy and computational efficiency using a simulated biological phantom and publically available experimental datasets of electron tomography. The numerical and visual evaluations of the experiments show that the adaptive multiresolution method can provide more accurate results than the weighted back projection (WBP), simultaneous iterative reconstruction technique (SIRT), and sequential MAP expectation maximization (sMAPEM) method. The method is superior to sMAPEM also in terms of computation time and usability since it can reconstruct 3D images significantly faster without requiring any parameter to be set by the user.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Signal Processing, BioMediTech
Contributors: Acar, E., Peltonen, S., Ruotsalainen, U.
Number of pages: 11
Pages: 24-34
Publication date: 1 Nov 2016
Peer-reviewed: Yes

Publication information

Journal: Ultramicroscopy
Volume: 170
ISSN (Print): 0304-3991
Ratings: 
  • Scopus rating (2016): CiteScore 2.82 SJR 1.896 SNIP 1.184
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Atomic and Molecular Physics, and Optics, Instrumentation
Keywords: Adaptive reconstruction, Electron tomography (ET), Maximum a posteriori (MAP) reconstruction, Missing wedge, Multiresolution reconstruction, Regularization parameter
Source: Scopus
Source ID: 84981309739

Research output: Contribution to journalArticleScientificpeer-review

Surface topography studied by off-axis digital holography

The topography of surface relief gratings patterned on As2S3–Se nanomultilayers was investigated by digital holographic microscopy. For the high-accuracy phase reconstruction of the topography we used the sparse wavefront modeling. Experimental results are presented.

General information

Publication status: Published
MoE publication type: D3 Professional conference proceedings
Organisations: Signal Processing, Research group: Computational Imaging-CI, Institute of Applied Physics Academy of Sciences of Moldava, University of Stuttgart
Contributors: Achimova, E., Abaskin, V., Cazac, V., Meshalkin, A., Pedrini, G., Claus, D., Shevkunov, I., Katkovnik, V.
Publication date: 2018

Host publication information

Title of host publication: Novel Optical Materials and Applications, NOMA 2018
Volume: Part F107-NOMA 2018
Publisher: OSA - The Optical Society
ISBN (Electronic): 9781557528209
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Mechanics of Materials
Source: Scopus
Source ID: 85051277835

Research output: Chapter in Book/Report/Conference proceedingConference contributionProfessional

Finite element method incorporating coupled magneto-elastic model for magneto-mechanical energy harvester

This paper presents a numerical method for modeling magneto-mechanical energy harvesting devices. Our existing energy-based
single-valued (SV) magneto-mechanical material model is utilized for the first time in a 2-D finite element formulation for an energy-
harvesting application. The SV material model yields the magnetic field strength as a function of strain and magnetic flux density. The
proposed method can predict the voltage induced in a pickup coil due to inverse magnetostriction, when the test sample is subjected to
dynamic loading. The results from the numerical method are experimentally verified using a prototype energy harvester.

General information

Publication status: Published
Organisations: Electrical Energy Engineering, Civil Engineering, Research group: Electromechanics, Research area: Power engineering
Contributors: Ahmed, U., Harju, J., Poutala, J., Ruuskanen, P., Rasilo, P., Kouhia, R.
Number of pages: 2
Publication date: 19 Jun 2017
Peer-reviewed: Unknown
Event: Paper presented at Compumag 2017, Daejeon, Korea, Democratic People's Republic of.
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials
Keywords: Magnetostriction, Energy harvesting, Coupled problems, Finite element analysis, Magneto elastic, stress
Electronic versions: 
URLs: 

Bibliographical note

The 2 pages digest was presented as poster presentation during conference.
INT="Harju, Jarmo"
INT="Ruuskanen, Pekka"

Research output: Other conference contributionPaper, poster or abstractScientific

Composition dependent growth dynamics in molecular beam epitaxy of GaInNAs solar cells

We have investigated the role of the nitrogen content, the growth parameters, and the annealing processes involved in molecular beam epitaxy of GaInNAs solar cells lattice-matched to GaAs. The nitrogen composition was varied between 1% and 5%. The influence of the growth temperature was assessed by performing photoluminescence, atomic force microscopy, X-ray diffraction, reflection high-energy electron diffraction, quantum efficiency and light-biased current-voltage measurements. The growth temperature ensuring the best cell parameters was found to be 440 C. At this temperature we were able to incorporate up to 4% of nitrogen and achieve a good material quality. Further increase of the N composition to 5% led to phase separation. For the lattice matched samples grown within the optimal temperature range, we have identified a clear (1×3) surface reconstruction. Using the optimized growth we have demonstrated a GaInNAs p-i-n solar cell structure containing 4% nitrogen, that exhibited a short-circuit current density as high as 33.8 mA/cm2 in respect to effective area illuminated. These measurements have been performed under real sun AM1.5 (~1000 W/m2) illumination. © 2014 Elsevier B.V.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Optoelectronics Research Centre, Frontier Photonics, Department of Physics and Astronomy, University of Turku, Turun Yliopisto/Turun Biomateriaalikeskus
Contributors: Aho, A., Polojärvi, V., Korpijärvi, V. M., Salmi, J., Tukiainen, A., Laukkanen, P., Guina, M.
Number of pages: 9
Pages: 150-158
Publication date: May 2014
Peer-reviewed: Yes

Publication information

Journal: Solar Energy Materials and Solar Cells
Volume: 124
ISSN (Print): 0927-0248
Ratings: 
  • Scopus rating (2014): CiteScore 5.87 SJR 2.19 SNIP 2.368
Original language: English
ASJC Scopus subject areas: Renewable Energy, Sustainability and the Environment, Electronic, Optical and Magnetic Materials, Surfaces, Coatings and Films
Keywords: Concentrated photovoltaics, Dilute nitrides, GaInNAs, Multi-junction solar cells, Plasma-assisted molecular beam epitaxy

Bibliographical note

Contribution: organisation=orc,FACT1=1<br/>Portfolio EDEND: 2014-04-29<br/>Publisher name: Elsevier

Source: researchoutputwizard
Source ID: 58

Research output: Contribution to journalArticleScientificpeer-review

Dilute nitride triple junction solar cells for space applications: Progress towards highest AM0 efficiency

We report a detailed performance assessment of triple junction dilute nitride solar cells fabricated by a combined molecular beam epitaxy-metal organic chemical vapor deposition process and designed for space applications. The experimental sample exhibits an efficiency level of 30.8% under AM0 illumination. Analyses of the isotype single junction dilute nitride bottom cells reveal a band gap voltage offset of 0.49 V at one sun illumination and a value as low as 0.47 V for full spectrum excitation without filter layers. The analyses point out the limitation of the design in terms of current balancing. With optimized design, an efficiency of 32.1% is possible, revealing the maturity reached by dilute nitride technology in the quest for improving the efficiency of lattice-matched multijunction solar cells.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Photonics, Research group: ORC, CESI S.p.A.
Contributors: Aho, A., Isoaho, R., Tukiainen, A., Gori, G., Campesato, R., Guina, M.
Number of pages: 5
Pages: 740-744
Publication date: Sep 2018
Peer-reviewed: Yes
Early online date: Apr 2018

Publication information

Journal: Progress in Photovoltaics: Research and Applications
Volume: 26
Issue number: 19
ISSN (Print): 1062-7995
Ratings: 
  • Scopus rating (2018): CiteScore 6.68 SJR 1.942 SNIP 2.42
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Renewable Energy, Sustainability and the Environment, Condensed Matter Physics, Electrical and Electronic Engineering
Source: Scopus
Source ID: 85045098254

Research output: Contribution to journalArticleScientificpeer-review

Back Reflector with Diffractive Gratings for Light-Trapping in Thin-Film III-V Solar Cells

We report on the development of light-trapping architectures applied to thin-film solar cells. In particular, we focus on enhancing the absorption at 1-eV spectral range for dilute nitride and quantum dot materials and report on the influence of planar back reflectors on the photovoltaic properties. Moreover, we discuss the properties of polymer diffraction gratings with enhanced light-trapping capability pointing to advantageous properties of pyramidal gratings. In order to understand the suitability of these polymer grating architectures for space applications, we have performed an electron irradiation study (1 MeV) revealing the absence of reflectance changes up to doses of 1×10 15 e-/cm 2 .

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Physics, Research group: ORC, Politecnico di Torino
Contributors: Aho, T., Tukiainen, A., Elsehrawy, F., Ranta, S., Raappana, M., Aho, A., Isoaho, R., Cappelluti, F., Guina, M.
Number of pages: 4
Publication date: 2019

Host publication information

Title of host publication:  2019 European Space Power Conference (ESPC)
Publisher: IEEE
ISBN (Print): 978-1-7281-2127-7
ISBN (Electronic): 978-1-7281-2126-0
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Renewable Energy, Sustainability and the Environment
Keywords: Solar Cell, Semiconducting III-V Materials

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Polymer stabilization enhances the orientational optical nonlinearity of oligothiophene-doped nematic liquid crystals

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Frontier Photonics, Tokyo Institute of Technology, Aalto University
Contributors: Aihara, Y., Kinoshita, M., Wang, J., Mamiya, J. I., Priimagi, A., Shishido, A.
Number of pages: 5
Pages: 787-791
Publication date: Nov 2013
Peer-reviewed: Yes

Publication information

Journal: Advanced Optical Materials
Volume: 1
Issue number: 11
ISSN (Print): 2195-1071
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Atomic and Molecular Physics, and Optics
Keywords: Liquid crystals, Nonlinear optics, Oligothiophenes, Optical nonlinearity, Polymer stabilization
Source: Scopus
Source ID: 84888056420

Research output: Contribution to journalArticleScientificpeer-review

Toward Graphene-Based Passive UHF RFID Textile Tags: A Reliability Study

This paper discusses the fabrication, wireless performance, and reliability of graphene-based passive ultrahigh-frequency radio-frequency identification (RFID) tags on a fabric substrate. The conductive ink comprising functionalized graphene nanoplatelets is deposited directly on a cotton fabric substrate to fabricate the tag antennas. After attaching the chips, the tag performance is evaluated through wireless tag measurements before and after high-humidity conditions, bending, and stretching. Initially, the peak read range of the tag is about 1.6 m, which increases to 3.2 m in 100% humidity conditions. Additionally, after drying, the performance of the tag returns back to normal. In a bending test, the read range of a bent tag decreases below 1 m. Furthermore, the read range of the tag in a nonbended state gradually decreases and is about 1.1 m after 100 bending cycles. According to our measurements, stretching has a serious detrimental effect on these tags and they cannot be considered stretchable. However, these initial results show that this low-cost and eco-friendly graphene RFID tag has a remarkable and unique response to moisture and high reliability in harsh bending conditions. Overall, it also has a strong potential to be used in future wearable sensor applications.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Electronics and Communications Engineering, Research group: Wireless Identification and Sensing Systems Research Group
Contributors: Akbari, M., Virkki, J., Sydänheimo, L., Ukkonen, L.
Number of pages: 3
Pages: 429-431
Publication date: 1 Sep 2016
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Device and Materials Reliability
Volume: 16
Issue number: 3
ISSN (Print): 1530-4388
Ratings: 
  • Scopus rating (2016): CiteScore 1.78 SJR 0.444 SNIP 1.273
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Safety, Risk, Reliability and Quality, Electrical and Electronic Engineering
Keywords: Bending, graphene, humidity, radio-frequency identification (RFID), reliability, stretching, wearable antennas
Source: Scopus
Source ID: 84986587064

Research output: Contribution to journalLetterScientificpeer-review

Roadmap on optical rogue waves and extreme events

The pioneering paper 'Optical rogue waves' by Solli et al (2007 Nature 450 1054) started the new subfield in optics. This work launched a great deal of activity on this novel subject. As a result, the initial concept has expanded and has been enriched by new ideas. Various approaches have been suggested since then. A fresh look at the older results and new discoveries has been undertaken, stimulated by the concept of 'optical rogue waves'. Presently, there may not by a unique view on how this new scientific term should be used and developed. There is nothing surprising when the opinion of the experts diverge in any new field of research. After all, rogue waves may appear for a multiplicity of reasons and not necessarily only in optical fibers and not only in the process of supercontinuum generation. We know by now that rogue waves may be generated by lasers, appear in wide aperture cavities, in plasmas and in a variety of other optical systems. Theorists, in turn, have suggested many other situations when rogue waves may be observed. The strict definition of a rogue wave is still an open question. For example, it has been suggested that it is defined as 'an optical pulse whose amplitude or intensity is much higher than that of the surrounding pulses'. This definition (as suggested by a peer reviewer) is clear at the intuitive level and can be easily extended to the case of spatial beams although additional clarifications are still needed. An extended definition has been presented earlier by N Akhmediev and E Pelinovsky (2010 Eur. Phys. J. Spec. Top. 185 1-4). Discussions along these lines are always useful and all new approaches stimulate research and encourage discoveries of new phenomena. Despite the potentially existing disagreements, the scientific terms 'optical rogue waves' and 'extreme events' do exist. Therefore coordination of our efforts in either unifying the concept or in introducing alternative definitions must be continued. From this point of view, a number of the scientists who work in this area of research have come together to present their research in a single review article that will greatly benefit all interested parties of this research direction. Whether the authors of this 'roadmap' have similar views or different from the original concept, the potential reader of the review will enrich their knowledge by encountering most of the existing views on the subject. Previously, a special issue on optical rogue waves (2013 J. Opt. 15 060201) was successful in achieving this goal but over two years have passed and more material has been published in this quickly emerging subject. Thus, it is time for a roadmap that may stimulate and encourage further research.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Physics, Australian National University, Université de Bourgogne Franche-Comté, Universita degli Studi di Brescia, Texas A and M University at Qatar, Shunde Polytechnic, Xi'an Jiaotong University, CSIC - Instituto de &amp;Oacute;ptica Daza de Vald&amp;eacute;s (IO), CRPP, Universidad Adolfo Ibánez, Université libre de Bruxelles (ULB), Vrije Universiteit Brussel, Université Lille 1, Université de Franche-Comté, Leibniz-Universität Hannover, Weierstrass-Institut für Angewandte Analysis und Stochastik, Max Born Institute, Universitat Politécnica de Catalunya, The University of Auckland, Dodd-Walls Centre for Photonic and Quantum Technologies, CNRS, CNR-INO
Contributors: Akhmediev, N., Kibler, B., Baronio, F., Belić, M., Zhong, W. P., Zhang, Y., Chang, W., Soto-Crespo, J. M., Vouzas, P., Grelu, P., Lecaplain, C., Hammani, K., Rica, S., Picozzi, A., Tlidi, M., Panajotov, K., Mussot, A., Bendahmane, A., Szriftgiser, P., Genty, G., Dudley, J., Kudlinski, A., Demircan, A., Morgner, U., Amiraranashvili, S., Bree, C., Steinmeyer, G., Masoller, C., Broderick, N. G. R., Runge, A. F. J., Erkintalo, M., Residori, S., Bortolozzo, U., Arecchi, F. T., Wabnitz, S., Tiofack, C. G., Coulibaly, S., Taki, M.
Publication date: 1 Jun 2016
Peer-reviewed: Yes

Publication information

Journal: Journal of Optics
Volume: 18
Issue number: 6
Article number: 063001
ISSN (Print): 2040-8978
Ratings: 
  • Scopus rating (2016): CiteScore 1.63 SJR 0.715 SNIP 0.829
Original language: English
ASJC Scopus subject areas: Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials
Keywords: extreme events, nonlinear optics, rogue waves

Bibliographical note

EXT="Steinmeyer, Günter"
EXT="Erkintalo, Miro"

Source: Scopus
Source ID: 84975818584

Research output: Contribution to journalArticleScientificpeer-review

Soliton enhancement of spontaneous symmetry breaking

Spontaneous symmetry breaking (SSB) occurs when noise triggers an initially symmetric system to evolve toward one of its nonsymmetric states. Topological and optical SSB involve material reconfiguration/transition and light propagation/distribution in time or space, respectively. In anisotropic optical media, light beam propagation and distribution of the optic axis can be linked, thereby connecting topological and optical SSB. Using nonlinear soft matter, namely uniaxial liquid crystals, we report on simultaneous topological and optical SSB, showing that spatial solitons enhance the noise-driven transition of the medium from a symmetric to an asymmetric configuration, while acquiring a power-dependent transverse velocity in either of two specular directions with respect to the initial wavevector. Solitons enhance SSB by further distorting the optic axis distribution through nonlinear reorientation, resulting in power-tunable walk-off as well as hysteresis in beam refraction versus angle of incidence.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Physics, Research group: Nonlinear Optics, Frontier Photonics, University “Roma Tre”, University of Southampton, United Kingdom
Contributors: Alberucci, A., Piccardi, A., Kravets, N., Buchnev, O., Assanto, G.
Number of pages: 7
Pages: 783-789
Publication date: 2015
Peer-reviewed: Yes

Publication information

Journal: Optica
Volume: 2
Issue number: 9
ISSN (Print): 2334-2536
Ratings: 
  • Scopus rating (2015): CiteScore 7 SJR 4.539 SNIP 2.629
Original language: English
ASJC Scopus subject areas: Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials
Keywords: Bistability, Instabilities and chaos, Liquid crystals, Nonlinear optics, Self-action effects, Spatial solitons, Transverse effects in
Source: Scopus
Source ID: 84941123130

Research output: Contribution to journalArticleScientificpeer-review

The red, purple and blue modifications of polymeric unsymmetrical hydroxyalkadiynyl-N-arylcarbamate derivatives in Langmuir-Schaefer films

Solid topochemical photopolymerization (STP) of Langmuir-Schaefer films of a new class of unsymmetrical diynes, containing N-arylcarbamate groups in the hydrophobic part and hydroxymethylene groups in the hydrophilic part of the molecules was examined. In addition, the monomeric Langmuir monolayer formation was studied by Brewster angle microscopy and the surface morphology of monomer and polymer films on solid substrates were studied by scanning electron microscopy and atomic force microscopy. Three phases of polydiacetylene (PDA) (red, purple and blue) were observed after UV-light polymerization of above-mentioned films of alcohol diacetylene (DA) derivatives. The substitution of MeO group in the aryl ring substituent by hydrogen atom and the variation of the methylene group number in the hydrophobic part from 5 to 6 changed significantly the result of STP: instead of blue phase PDA observed for diynes with MeO group, the red phase PDA was observed for DA with H-atom from the very beginning of diyne film UV irradiation. For two other diynilic N-arylcarbamates of identical chemical structures except of the substituents in the aryl ring of hydrophobic parts of the molecules, no changes in the efficiency of polymerization or the position and shape of absorption bands were observed. This indicated the formation of the purple phase PDA. For these molecules, the number of methylene groups in hydrophobic and hydrophilic parts of the molecules was 9 and 2, respectively.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Chemistry and Bioengineering, Research group: Supramolecular photochemistry, A. M. Prokhorov General Physics Institute, Russian Academy of Sciences, Åbo Akademi University, St. Petersburg State University, NRC Kurchatov Institute, Russian Acad Sci, Russian Academy of Sciences, Kotelnikov Inst Radio Engn & Elect
Contributors: Alekseev, A., Ihalainen, P., Ivanov, A., Domnin, I., Klechkovskaya, V., Orekhov, A., Lemmetyinen, H., Vuorimaa-Laukkanen, E., Peltonen, J., Vyaz'min, S.
Number of pages: 9
Pages: 463-471
Publication date: 1 Aug 2016
Peer-reviewed: Yes

Publication information

Journal: Thin Solid Films
Volume: 612
ISSN (Print): 0040-6090
Ratings: 
  • Scopus rating (2016): CiteScore 1.83 SJR 0.639 SNIP 0.863
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Materials Chemistry, Metals and Alloys, Surfaces, Coatings and Films, Surfaces and Interfaces
Keywords: Langmuir monolayer, Langmuir-Schaefer film, Polydiacetylenes with urethane group, Solid topochemical photopolymerization

Bibliographical note

EXT="Alekseev, Alexander"

Source: Scopus
Source ID: 84976884439

Research output: Contribution to journalArticleScientificpeer-review

Stable blue phase polymeric Langmuir-Schaefer films based on unsymmetrical hydroxyalkadiynyl N-arylcarbamate derivatives

Unsymmetrical diynes containing N-arylcarbamate groups in the hydrophobic part and hydroxymethylene groups in the hydrophilic part of the molecules were synthesized and studied. The Langmuir monolayer formation process was followed by Brewster angle microscopy (BAM). The Langmuir-Schaefer monolayer films, transferred on solid substrates (quartz or Si), were investigated by absorption spectroscopy and atomic force microscopy (AFM). Four substances had 2 methylene groups in the hydrophilic part of the molecule (n) and 4 or 5 of these groups in the hydrophobic part (m). At the same time the aryl substituent had a hydrogen atom or a MeO group in the p-position of the benzene ring. After 20 min of UV irradiation the initially colorless monomeric films of all four compounds turned into stable blue phase polymeric films. The blue phase is unusual for alcoholic diacetylene derivatives. The BAM and AFM measurements demonstrated higher homogeneity of the films with a MeO group in the aryl substituent in comparison to the molecules with a hydrogen atom. The reasons for these different structural organizations as well as potential applications of stable blue phase polydiacetylene thin films are discussed.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Chemistry and Bioengineering, Research group: Chemistry & Advanced Materials, A. M. Prokhorov General Physics Institute, Russian Academy of Sciences, Åbo Akademi University, St. Petersburg State University, Russian Academy of Science
Contributors: Alekseev, A., Ihalainen, P., Ivanov, A., Domnin, I., Rosqvist, E., Lemmetyinen, H., Vuorimaa-Laukkanen, E., Peltonen, J., Vyaz'min, S.
Number of pages: 11
Pages: 108-118
Publication date: 2018
Peer-reviewed: Yes
Early online date: 10 Oct 2017

Publication information

Journal: Thin Solid Films
Volume: 645
ISSN (Print): 0040-6090
Ratings: 
  • Scopus rating (2018): CiteScore 1.91 SJR 0.531 SNIP 0.837
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Surfaces and Interfaces, Surfaces, Coatings and Films, Metals and Alloys, Materials Chemistry
Keywords: Absorption spectroscopy, Blue phase polydiacetylenes, Brewster angle microscopy, Langmuir-Schaefer film, Photopolymerization

Bibliographical note

EXT="Alekseev, Alexander"

Source: Scopus
Source ID: 85032302551

Research output: Contribution to journalArticleScientificpeer-review

Ambient-Pressure XPS Study of a Ni-Fe Electrocatalyst for the Oxygen Evolution Reaction

Chemical analysis of solid-liquid interfaces under electrochemical conditions has recently become feasible due to the development of new synchrotron radiation techniques. Here we report the use of "tender" X-ray ambient-pressure X-ray photoelectron spectroscopy (APXPS) to characterize a thin film of Ni-Fe oxyhydroxide electrodeposited on Au as the working electrode at different applied potentials in 0.1 M KOH as the electrolyte. Our results show that the as-prepared 7 nm thick Ni-Fe (50% Fe) film contains Fe and Ni in both their metallic as well as oxidized states, and undergoes further oxidation when the sample is subjected to electrochemical oxidation-reduction cycles. Metallic Fe is oxidized to Fe3+ and metallic Ni to Ni2+/3+. This work shows that it is possible to monitor the chemical nature of the Ni-Fe catalyst as a function of potential when the corresponding current densities are small. This allows for operando measurements just above the onset of OER; however, current densities as they are desired in photoelectrochemical devices (∼1-10 mA cm-2) could not be achieved in this work, due to ohmic losses in the thin electrolyte film. We use a two-dimensional model to describe the spatial distribution of the electrochemical potential, current density, and pH as a function of the position above the electrolyte meniscus, to provide guidance toward enabling the acquisition of operando APXPS at high current density. The shifts in binding energy of water with applied potential predicted by the model are in good agreement with the experimental values.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Optoelectronics Research Centre, Research group: Surface Science, SUNCAT Center for Interface Science and Catalysis, SLAC National Accelerator Laboratory, Department of Chemical and Biomolecular Engineering, Berkeley, Materials Sciences Division, Lawrence Berkeley National Laboratory, Materials and Corrosion Engineering, Exponent, Inc., Polymer Science and Materials Chemistry
Contributors: Ali-Löytty, H., Louie, M. W., Singh, M. R., Li, L., Sanchez Casalongue, H. G., Ogasawara, H., Crumlin, E. J., Liu, Z., Bell, A. T., Nilsson, A., Friebel, D.
Number of pages: 7
Pages: 2247-2253
Publication date: 4 Feb 2016
Peer-reviewed: Yes

Publication information

Journal: Journal of Physical Chemistry C
Volume: 120
Issue number: 4
ISSN (Print): 1932-7447
Ratings: 
  • Scopus rating (2016): CiteScore 4.48 SJR 1.964 SNIP 1.189
Original language: English
ASJC Scopus subject areas: Physical and Theoretical Chemistry, Electronic, Optical and Magnetic Materials, Surfaces, Coatings and Films, Energy(all)
Electronic versions: 
URLs: 
Source: Scopus
Source ID: 84957588014

Research output: Contribution to journalArticleScientificpeer-review

Laser angle-resolved photoemission as a probe of initial state kz dispersion, final-state band gaps, and spin texture of Dirac states in the Bi2 Te3 topological insulator

We have obtained angle-resolved photoemission spectroscopy (ARPES) spectra from single crystals of the topological insulator material Bi2Te3 using a tunable laser spectrometer. The spectra were collected for 11 different photon energies ranging from 5.57 to 6.70 eV for incident light polarized linearly along two different in-plane directions. Parallel first-principles, fully relativistic computations of photointensities were carried out using the experimental geometry within the framework of the one-step model of photoemission. A reasonable overall accord between theory and experiment is used to gain insight into how properties of the initial- and final-state band structures as well as those of the topological surface states and their spin textures are reflected in the laser-ARPES spectra. Our analysis reveals that laser-ARPES is sensitive to both the initial-state kz dispersion and the presence of delicate gaps in the final-state electronic spectrum.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Physics, Research area: Computational Physics, Research group: Spectroscopies of Complex Materials, Ames Laboratory, Iowa State University, Northeastern University
Contributors: Ärrälä, M., Hafiz, H., Mou, D., Wu, Y., Jiang, R., Riedemann, T., Lograsso, T. A., Barbiellini, B., Kaminski, A., Bansil, A., Lindroos, M.
Number of pages: 7
Publication date: 27 Oct 2016
Peer-reviewed: Yes

Publication information

Journal: Physical Review B
Volume: 94
Issue number: 15
Article number: 155144
ISSN (Print): 1098-0121
Ratings: 
  • Scopus rating (2016): CiteScore 3.16 SJR 2.339 SNIP 1.183
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Source: Scopus
Source ID: 84994236456

Research output: Contribution to journalArticleScientificpeer-review

Persistent luminescent glasses prepared using the direct doping method

We review our work on the development of persistent luminescent (PeL) glasses with different compositions. The direct doping method used for preparation of such glasses is explained. Special attention is paid to the stability of the PeL microparticles (MPs) in the glasses during the glass preparation. We demonstrate that the MPs stability is not only sensitive to the melting conditions but also to the glass composition.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Physics, Tampere University, Leibniz Institute of Photonic Technology e.V., Turun yliopisto, Kyoto University
Contributors: Aryal, U., Ojha, N., Trautvetter, T., Lastusaari, M., Ueda, J., Mueller, R., Veber, A., Petit, L.
Publication date: 1 Jul 2019

Host publication information

Title of host publication: 21st International Conference on Transparent Optical Networks, ICTON 2019
Publisher: IEEE
ISBN (Electronic): 9781728127798

Publication series

Name: International Conference on Transparent Optical Networks
ISSN (Electronic): 2161-2064
ASJC Scopus subject areas: Computer Networks and Communications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials
Keywords: Direct doping method, Particles, Persistent luminescence, Phosphate glasses
Source: Scopus
Source ID: 85073059546

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Electro-optic steering of nematicons

We study the angular steering of spatial solitons in nematic liquid crystals, i.e. nematicons, exploiting their electro-optic response. Approaches to electro-optic steering include acting on the optic axis and walk-off, propagating the soliton through a voltage-adjusted refractive interface or getting it totally internally reflected. Using comb electrodes in a planar cell, maximum angular deflections of 70° are expected with the standard nematic liquid crystal mixture E7.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Frontier Photonics, Nonlinear Optics and OptoElectronics Lab, University “Roma Tre”
Contributors: Assanto, G., Piccardi, A., Barboza, R., Alberucci, A.
Number of pages: 3
Pages: 2-4
Publication date: 2012
Peer-reviewed: Yes

Publication information

Journal: Photonics Letters of Poland
Volume: 4
Issue number: 1
Ratings: 
  • Scopus rating (2012): CiteScore 1.1 SJR 0.328 SNIP 0.581
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials
Source: Scopus
Source ID: 84859416329

Research output: Contribution to journalArticleScientificpeer-review

Liquid crystal light valves: A versatile platform for nematicons

We illustrate the generation and control of optical spatial solitary waves (nematicons) in liquid crystal light valves with nematic liquid crystals and a photoconductive layer. The latter allows to all-optically varying the birefringent walk-off and the extraordinary-wave refractive index, hence, the trajectory of a nematicon propagating in the thickness of the valve.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Univ Roma Tre, Roma Tre University, Dept Elect Engn, NooEL, University “Roma Tre”, CNRS
Contributors: Assanto, G., Piccardi, A., Alberucci, A., Residori, S., Bortolozzo, U.
Number of pages: 3
Pages: 151-153
Publication date: 2009
Peer-reviewed: Yes

Publication information

Journal: Photonics Letters of Poland
Volume: 1
Issue number: 4
ISSN (Print): 2080-2242
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials
Source: Scopus
Source ID: 78650977780

Research output: Contribution to journalArticleScientificpeer-review

Nonlinear optics applications: In memory of George I. Stegeman

General information

Publication status: Published
MoE publication type: B1 Article in a scientific magazine
Organisations: Department of Physics, Aerosol Physics Laboratory, Nonlinear Optics and OptoElectronics Lab, University “Roma Tre”
Contributors: Assanto, G.
Number of pages: 1
Pages: 1
Publication date: 2016
Peer-reviewed: No

Publication information

Journal: Photonics Letters of Poland
Volume: 8
Issue number: 1
ISSN (Print): 2080-2242
Ratings: 
  • Scopus rating (2016): CiteScore 0.37 SJR 0.197 SNIP 0.272
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials
Source: Scopus
Source ID: 84962141630

Research output: Contribution to journalEditorialScientific

Nonlinear guided waves: Preface

This special issue presents a collection of experimental and theoretical research in nonlinear waves, with emphasis on nonlinear optics, which were presented at the conference Nonlinear Guided Waves VIII held at the Hotel Victoria, Oaxaca, Mexico in April 2016. This preface provides a short history of the conference series Nonlinear Guided Waves and short introductions to the contributed papers which puts them in context.

General information

Publication status: Published
MoE publication type: B1 Article in a scientific magazine
Organisations: Photonics, Nonlinear Optics and OptoElectronics Lab, University “Roma Tre”, Optics Laboratory, Department of Physics, Tampere University of Technology, CNR-ISC, Institute for Complex Systems, University of Edinburgh
Contributors: Assanto, G., Smyth, N. F.
Publication date: 1 Dec 2016
Peer-reviewed: No

Publication information

Journal: Journal of Nonlinear Optical Physics and Materials
Volume: 25
Issue number: 4
Article number: 1650041
ISSN (Print): 0218-8635
Ratings: 
  • Scopus rating (2016): CiteScore 0.81 SJR 0.301 SNIP 0.493
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Atomic and Molecular Physics, and Optics, Physics and Astronomy (miscellaneous)
Keywords: discrete systems, Nonlinear optics, solitary waves, solitons
Source: Scopus
Source ID: 85011382866

Research output: Contribution to journalArticleScientific

Refraction of nonlinear light beams in nematic liquid crystals

We use modulation theory to analyze the interaction of optical solitons and vortices with a dielectric interface between two regions of nematic liquid crystals. In the analysis we consider the role of nonlocality, anisotropy and nonlinear reorientation and compare modulation theory results with numerical results. Upon interacting with the interface, nematicons undergo transverse distortion but remain stable and eventually return to a steady state, whereas vortices experience an enhanced instability and can break up into bright beams or solitary waves.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Frontier Photonics, Nonlinear Optics and OptoElectronics Lab, University of Edinburgh
Contributors: Assanto, G., Smyth, N. F., Xia, W.
Publication date: Sep 2012
Peer-reviewed: Yes

Publication information

Journal: Journal of Nonlinear Optical Physics and Materials
Volume: 21
Issue number: 3
Article number: 1250033
ISSN (Print): 0218-8635
Ratings: 
  • Scopus rating (2012): CiteScore 0.55 SJR 0.299 SNIP 0.324
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Atomic and Molecular Physics, and Optics, Physics and Astronomy (miscellaneous)
Keywords: Liquid crystal, modulation theory, nematicon, refraction, soliton
Source: Scopus
Source ID: 84871342982

Research output: Contribution to journalArticleScientificpeer-review

Electro-optic steering of random laser emission in liquid crystals

Using an external low-frequency electric field applied to dye-doped nematic liquid crystals, we demonstrate that random lasing obtained by optical pumping can be steered in an angular direction by routing an all-optical waveguide able to collect the emitted light. By varying the applied voltage from 0 to 2 V, we reduce the walk-off and sweep the random laser guided beam over 7 degrees.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Physics, Research group: Nonlinear Optics, University of Rome Roma Tre, University “Roma Tre”
Contributors: Assanto, G., Perumbilavil, S., Piccardi, A., Kauranen, M.
Number of pages: 3
Pages: 103-105
Publication date: 2018
Peer-reviewed: Yes

Publication information

Journal: Photonics Letters of Poland
Volume: 10
Issue number: 4
ISSN (Print): 2080-2242
Ratings: 
  • Scopus rating (2018): CiteScore 0.52 SJR 0.214 SNIP 0.357
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials
Source: Scopus
Source ID: 85062032353

Research output: Contribution to journalArticleScientificpeer-review

Rapid and sensitive detection of norovirus antibodies in human serum with a biolayer interferometry biosensor

Here, we describe the use of a biolayer interferometry biosensor for the fast and sensitive detection of virus-specific antibodies from human serum samples. Norovirus-like particles and norovirus P-particles were used to functionalise the biosensor tip. The detection of antibodies directly from serum samples was challenging, but the addition of a metal chelator (DAB) combined with an anti-human horseradish peroxidase-tagged antibody enabled enhanced detection of virus-specific antibodies in serum dilutions up to 1:100,000. Biolayer interferometry provides results faster than an ELISA, with results in as little as 10-20 min when using pre-functionalised sensors. Therefore, biolayer interferometry combined with DAB enhancement offers an attractive method for quick and sensitive quantification of biomolecules from complicated sample matrices.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Multi-scaled biodata analysis and modelling (MultiBAM), Fimlab Laboratories Ltd
Contributors: Auer, S., Koho, T., Uusi-Kerttula, H., Vesikari, T., Blazevic, V., Hytönen, V. P.
Number of pages: 8
Pages: 507-514
Publication date: 31 Dec 2015
Peer-reviewed: Yes

Publication information

Journal: Sensors and Actuators B: Chemical
Volume: 221
ISSN (Print): 0925-4005
Ratings: 
  • Scopus rating (2015): CiteScore 4.84 SJR 1.225 SNIP 1.486
Original language: English
ASJC Scopus subject areas: Electrical and Electronic Engineering, Condensed Matter Physics, Electronic, Optical and Magnetic Materials, Metals and Alloys, Surfaces, Coatings and Films, Materials Chemistry, Instrumentation
Keywords: Biolayer interferometry, Fast diagnostics, Non-labelled detection, Norovirus, P-particles, Virus-like particles (VLPs)
Source: Scopus
Source ID: 84956972181

Research output: Contribution to journalArticleScientificpeer-review

Long-Range Observation of Exciplex Formation and Decay Mediated by One-Dimensional Bridges

We report herein unprecedented long-range observation of both formation and decay of the exciplex state in donor (D)-bridge (B)-acceptor (A) linked systems. Zinc porphyrins (ZnP) as a donor were tethered to single-walled carbon nanotube (SWNT) as an acceptor through oligo(p-phenylene)s (ZnP-phn-SWNT) or oligo(p-xylene)s (ZnP-xyn-1-ph1-SWNT) with systematically varied lengths (n = 1-5) to address the issue. Exponential dependencies of rate constants for the exciplex formation (kFEX) and decay (kDEX) on the edge-to-edge separation distance between ZnP and SWNT through the bridges were unambiguously derived from time-resolved spectroscopies. Distance dependencies (i.e., attenuation factor, β) of kFEX and kDEX in ZnP-phn-SWNT were found to be considerably small (β = 0.10 for kFEX and 0.12 Å-1 for kDEX) compared to those for charge separation and recombination (0.2-0.8 Å-1) in D-B-A systems with the same oligo(p-phenylene) bridges. The small β values may be associated with the exciplex state with mixed characters of charge-transfer and excited states. In parallel, the substantially nonconjugated bridge of oligo(p-xylene)s exhibited larger attenuation values (β = 0.12 for kFEX and 0.14 Å-1 for kDEX). These results provide deep insight into the unique photodynamics of electronically strongly coupled D-B-A systems involving exciplex.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Chemistry and Bioengineering, Research group: Chemistry & Advanced Materials, Kyoto Women's University
Contributors: Baek, J., Umeyama, T., Stranius, K., Yamada, H., Tkachenko, N. V., Imahori, H.
Number of pages: 10
Pages: 13952-13961
Publication date: 29 Jun 2017
Peer-reviewed: Yes

Publication information

Journal: Journal of Physical Chemistry C
Volume: 121
Issue number: 25
ISSN (Print): 1932-7447
Ratings: 
  • Scopus rating (2017): CiteScore 4.58 SJR 2.135 SNIP 1.133
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Energy(all), Surfaces, Coatings and Films, Physical and Theoretical Chemistry
Source: Scopus
Source ID: 85022231305

Research output: Contribution to journalArticleScientificpeer-review

Photophysical properties of porphyrin dimer-single-walled carbon nanotube linked systems

Porphyrin dimers were covalently grafted onto electron-accepting single-walled carbon nanotube (SWNT) sidewalls by direct aryl radical addition reaction with an m-or p-phenylene linker with the help of p-p interaction between the porphyrins. A splitting of the porphyrin Soret band and DFT calculations supported the selective formation of the porphyrin dimers on the sidewall of SWNTs. Photoexcitation of the porphyrin dimers on the SWNT resulted in the formation of the exciplex state, which directly decayed to the ground state without yielding the complete charge-separated state. Lifetimes of the porphyrin dimer-SWNT exciplex were longer than that of a porphyrin monomer-SWNT exciplex due to the stabilization by p-electron interaction over two porphyrin rings. In addition, the weaker electronic coupling through the meta-linkage than the para-one may be responsible for the exciplex lifetime of the porphyrin dimer-SWNT with the m-phenylene linker (49 ps) longer than that with the p-phenylene one (24 ps). The results obtained here provide the basic information on the effect of the donor dimerization on the photodynamic behavior of the exciplex state in donor-acceptor linked systems. [Figure presented]

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Chemistry and Bioengineering, Research group: Chemistry & Advanced Materials, Kyoto Women's University
Contributors: Baek, J., Umeyama, T., Mizuno, S., Tkachenko, N. V., Imahori, H.
Publication date: 2017
Peer-reviewed: Yes

Publication information

Journal: Journal of Physical Chemistry C
Volume: 121
Issue number: 39
ISSN (Print): 1932-7447
Ratings: 
  • Scopus rating (2017): CiteScore 4.58 SJR 2.135 SNIP 1.133
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Energy(all), Physical and Theoretical Chemistry, Surfaces, Coatings and Films
Source: Scopus
Source ID: 85032629899

Research output: Contribution to journalArticleScientificpeer-review

Test results of the LARP HQ02b magnet at 1.9 K

The HQ magnet is a 120-mm aperture, 1-m-long Nb3Sn quadrupole developed by the LARP collaboration in the framework of the High-Luminosity LHC project. A first series of coils was assembled and tested in five assemblies of the HQ01 series. The HQ01e model achieved a maximum gradient of 170 T/m at 4.5 K at LBNL in 2010-2011 and reached 184 T/m at 1.9 K at CERN in 2012. A new series of coils incorporating major design changes was fabricated for the HQ02 series. The first model, HQ02a, was tested at Fermilab where it reached 98% of the short sample limit at 4.5 K with a gradient of 182 T/m in 2013. However, the full training of the coils at 1.9 K could not be performed due to a current limit of 15 kA. Following this test, the azimuthal coil pre-load was increased by about 30 MPa and an additional current lead was installed at the electrical center of the magnet for quench protection studies. The test name of this magnet changed to HQ02b. In 2014, HQ02b was then shipped to CERN as the first opportunity for full training at 1.9 K. In this paper, we present a comprehensive summary of the HQ02 test results including: magnet training at 1.9 K with increased preload; quench origin and propagation; and ramp rate dependence. A series of powering tests was also performed to assess changes in magnet performance with a gradual increase of the MIITs. We also present the results of quench protection studies using different setting for detection, heater coverage, energy extraction and the coupling-loss induced quench (CLIQ) system.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Electrical Engineering, European Organization for Nuclear Research, CERN, Conseil Europeen pour la Recherche Nucleaire, Fermi National Accelerator Laboratory, Lawrence Berkeley National Laboratory, Brookhaven National Laboratory, University of Twente
Contributors: Bajas, H., Ambrosio, G., Anerella, M., Bajko, M., Bossert, R., Bottura, L., Caspi, S., Cheng, D., Chiuchiolo, A., Chlachidze, G., Dietderich, D., Felice, H., Ferracin, P., Feuvrier, J., Ghosh, A., Giloux, C., Godeke, A., Hafalia, A. R., Marchevsky, M., Ravaioli, E., Sabbi, G. L., Salmi, T., Schmalzle, J., Todesco, E., Wanderer, P., Wang, X., Yu, M.
Publication date: 1 Jun 2015
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Applied Superconductivity
Volume: 25
Issue number: 3
Article number: 4003306
ISSN (Print): 1051-8223
Ratings: 
  • Scopus rating (2015): CiteScore 1.27 SJR 0.403 SNIP 1.046
Original language: English
ASJC Scopus subject areas: Electrical and Electronic Engineering, Condensed Matter Physics, Electronic, Optical and Magnetic Materials
Keywords: Niobium-tin, quadrupole magnet, Superconducting coils
Source: Scopus
Source ID: 84924028983

Research output: Contribution to journalArticleScientificpeer-review

Cold test results of the LARP HQ Nb3Sn quadrupole magnet at 1.9 K

The high gradient quadrupole magnet is a 120-mm-aperture, 1-m-long Nb 3Sn quadrupole developed by the LHC Accelerator Research Program collaboration in support of the High-Luminosity LHC project. Several tests were performed at Lawrence Berkeley National Laboratory in 2010-2011 achieving a maximum gradient of 170 T/m at 4.4 K. As a next step in the program, the latest model (HQ01e) was sent to CERN for testing at 1.9 K. As part of this test campaign, the magnet training has been done up to a maximum current of 16.2 kA corresponding to 85% of the short sample limit. The ramp rate dependence of the quench current is also identified. The efficiency of the quench heaters is then studied at 4.2 K and at 1.9 K. The analyses of the magnet resistance evolution during fast current discharge showed evidence of quench whereas high energy quenches have been successfully achieved and sustained with no dump resistor.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Research area: Electromagnetics, European Organization for Nuclear Research, Fermi National Accelerator Laboratory, Brookhaven National Laboratory, Lawrence Berkeley National Laboratory
Contributors: Bajas, H., Ambrosio, G., Anerella, M., Bajko, M., Bossert, R., Caspi, S., Chiuchiolo, A., Chlachidze, G., Dietderich, D., Dunkel, O., Felice, H., Ferracin, P., Feuvrier, J., Fiscarelli, L., Ghosh, A., Giloux, C., Godeke, A., Hafalia, A. R., Marchevsky, M., Russenschuck, S., Sabbi, G. L., Salmi, T., Schmalzle, J., Todesco, E., Wanderer, P., Wang, X., Yu, M.
Publication date: 2013
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Applied Superconductivity
Volume: 23
Issue number: 3
Article number: 4002606
ISSN (Print): 1051-8223
Ratings: 
  • Scopus rating (2013): CiteScore 1.32 SJR 0.443 SNIP 1.148
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Electrical and Electronic Engineering
Keywords: High gradient quadrupole (HQ), LHC Accelerator Research Program (LARP), magnet protection, NbSnquadrupole
Source: Scopus
Source ID: 84878130018

Research output: Contribution to journalArticleScientificpeer-review

Compatibilization of natural rubber/nitrile rubber blends by sol–gel nano-silica generated by in situ method

Abstract: Controlled growth of in situ silica, into natural rubber (NR)/nitrile rubber (NBR) blend (40/60 composition by weight) following solution sol–gel method, results in a coherent blend morphology with enhanced composite properties. Similar composites, i.e., in situ silica-filled NR/NBR blend (40/60 by weight), showed better mechanical properties than any other composition that were prepared by soaking sol–gel method in earlier study. However, silica content in the rubber blend was limited to 20 phr (parts per hundred parts of rubber) and could not be increased under experimental condition following soaking sol–gel method. In the present work, silica content is increased (up to 30 phr) beyond that limit for the same blend composition. Accordingly, mechanical properties of the NR/NBR composites are improved. Use of a silane coupling agent, viz., bis-(3-triethoxysilylpropyl)-tetra sulfide, in the reactive sol–gel system during in situ silica generation brings in remarkable effect in silica distribution, rubber–filler interaction and mechanical properties of the composites. TEM micrographs of the selected composites reveal that silica is mostly grown at the interfacial region, when silane is used in particular. This results in further enhancement in mechanical properties and compatibility of the blend at the same silica content as evident from stress–strain and dynamic mechanical analysis studies. The reinforcement of effect in situ silica is assessed by Guth–Gold equation and modified form of Guth equation (with shape factor f = 2.53). The results are supported by the detailed studies on rheological, morphological, mechanical and viscoelastic properties of the composites. Graphical Abstract: [Figure not available: see fulltext.]

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Materials Science, Visvesvaraya National Institute of Technology, Indian Rubber Manufacturers Research Association, Department of Elastomers, Leibniz-Institut für Polymerforschung Dresden E.V., University of Kalyani
Contributors: Bansod, N. D., Kapgate, B. P., Das, C., Das, A., Basu, D., Debnath, S. C.
Number of pages: 12
Pages: 548–559
Publication date: 2016
Peer-reviewed: Yes

Publication information

Journal: JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY
Volume: 80
Issue number: 2
ISSN (Print): 0928-0707
Ratings: 
  • Scopus rating (2016): CiteScore 1.53 SJR 0.48 SNIP 0.678
Original language: English
ASJC Scopus subject areas: Chemistry(all), Condensed Matter Physics, Biomaterials, Ceramics and Composites, Electronic, Optical and Magnetic Materials, Materials Chemistry
Keywords: In situ silica, Reinforcement, Rubber blend, Rubber–filler interaction, Silane treatment, Sol–gel method
Source: Scopus
Source ID: 84974817789

Research output: Contribution to journalArticleScientificpeer-review

Mechanical characterization of pore-graded bioactive glass scaffolds produced by robocasting

Since the discovery of 45S5 Bioglass® by Larry Hench, bioactive glasses have been widely studied as bone substitute materials and, in more recent years, have also shown great promise for producing three-dimensional scaffolds. The development of additive manufacturing techniques and their application in bone tissue engineering allows the design and fabrication of complex structures with controlled porosity. However, achieving strong and mechanically-reliable bioactive glass scaffolds is still a great challenge. Furthermore, there is a relative paucity of studies reporting an exhaustive assessment of other mechanical properties than compressive strength of glass-derived scaffolds. This research work aimed at determining key mechanical properties of silicate SiO2-Na2O-K2OMgO-CaO-P2O5 glass scaffolds fabricated by robocasting and exhibiting a porosity gradient. When tested in compression, these scaffolds had a strength of 6 MPa, a Young's modulus around 340 MPa, a fracture energy of 93 kJ/m3 and a Weibull modulus of 3, which provides a quantification of the scaffold reliability and reproducibility. Robocasting was a suitable manufacturing method to obtain structures with favorable porosity and mechanical properties comparable to those of the human cancellous bone, which is fundamental regarding osteointegration of bone implants.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: BioMediTech, Politecnico di Torino, McGill University
Contributors: Barberi, J., Nommeots-Nomm, A., Fiume, E., Verné, E., Massera, J., Baino, F.
Number of pages: 8
Pages: 140-147
Publication date: 2019
Peer-reviewed: Yes

Publication information

Journal: Biomedical Glasses
Volume: 5
Issue number: 1
ISSN (Print): 2299-3932
Ratings: 
  • Scopus rating (2019): SJR 0.39 SNIP 1.056
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Ceramics and Composites, Surfaces, Coatings and Films, Materials Chemistry
Keywords: Bioactive glass, Mechanical properties, Robocasting, Scaffold

Bibliographical note

EXT="Nommeots-Nomm, Amy"

Source: Scopus
Source ID: 85078096149

Research output: Contribution to journalArticleScientificpeer-review

Localization of light at vanishingly small disorder-levels with heavy photons

We show that the key parameter driving the spatial extent of localized modes formed in randomly-perturbed periodic media near the band edge is the effective photon mass rather than the group index.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Frontier Photonics, CNRS, Université de Bordeaux, ICMCB, Laboratoire Photonique, CNRS-Univ. Bourgogne, University of Ottawa, Canada, University of York
Contributors: Baron, A., Faggiani, R., Zang, X., Lalouat, L., Schulz, S. A., Vynck, K., O'Regan, B., Cluzel, B., De Fornel, F., Krauss, T. F., Lalanne, P.
Publication date: 10 Aug 2015

Host publication information

Title of host publication: 2015 Conference on Lasers and Electro-Optics, CLEO 2015
Volume: 2015-August
Publisher: Optical Society of America OSA
Article number: 7183319
ISBN (Electronic): 9781557529688
ASJC Scopus subject areas: Electrical and Electronic Engineering, Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials
Keywords: Geometry, Indexes, Microscopy, Nonhomogeneous media, Optical waveguides, Photonics
Source: Scopus
Source ID: 84954056218

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

A perceptual quality metric for high-definition stereoscopic 3D video

The use of 3D video is growing in several fields such as entertainment, military simulations, medical applications. However, the process of recording, transmitting, and processing 3D video is prone to errors thus producing artifacts that may affect the perceived quality. Nowadays a challenging task is the definition of a new metric able to predict the perceived quality with low computational complexity in order to be used in real-time applications. The research in this field is very active due to the complexity of the analysis of the influence of stereoscopic cues. In this paper we present a novel stereoscopic metric based on the combination of relevant features able to predict the subjective quality rating in a more accurate way.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Department of Signal Processing, Research group: 3D MEDIA, Signal Processing Research Community (SPRC), Universita' degli Studi Roma TRE
Contributors: Battisti, F., Carli, M., Stramacci, A., Boev, A., Gotchev, A.
Publication date: 2015

Host publication information

Title of host publication: Image Processing: Algorithms and Systems XIII
Publisher: SPIE
Article number: 939916
ISBN (Print): 9781628414899

Publication series

Name: SPIE Conference Proceedings
Volume: 9399
ASJC Scopus subject areas: Applied Mathematics, Computer Science Applications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Keywords: Quality metric, Stereoscopic 3D video, Video transmission
Electronic versions: 
Source: Scopus
Source ID: 84928485494

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

A multi-band WCDMA SAW-less receivers with frequency selective feedback loop

For frequency division duplex (FDD) wide band code division multiple access (WCDMA) system, transmit (TX) signal leakage at the receiver input degrades the receiver performance. Previously, to cancel the TX leakage, a frequency selective feedback was proposed, but it had the unpredictable feedback loop characteristic due to the uncertainty of the duplexer impedance. This paper proposes a new method to achieve a predictable feedback loop characteristic. In addition, to achieve the TX leakage cancellation for multi-band, a local oscillator (LO) phase shift technique is also presented. The proposed receiver which was composed of high- and low-band LNAs and mixers, the TX canceller, and the LO shifter was implemented using 0.18-μm CMOS process and is under fabrication. Simulation results met the required specifications which were delivered from the WCDMA specifications.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Sensing Systems for Wireless Medicine (MediSense), Georgia Institute of Technology
Contributors: Beck, S., Kim, S. T., Lim, K., Tentzeris, M. M., Laskar, J.
Publication date: 2011

Host publication information

Title of host publication: 54th IEEE International Midwest Symposium on Circuits and Systems, MWSCAS 2011
Article number: 6026387
ISBN (Print): 9781612848570
ASJC Scopus subject areas: Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials
Source: Scopus
Source ID: 80053630391

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

A 0.5-6MHz Active-RC LPF with Fine Gain Steps Using Binary Interpolated Resistor Banks

This paper proposes an active-RC filter that achieves a wide pseudo-continuous bandwidth-tuning range and a wide gain range with fine steps using a novel switched resistor architecture. A channelselection filter with the proposed resistor bank is designed for a multi-mode mobile-TV receiver with the 6th order Chebyshev-I topology. The bandwidth, 0.5-6 MHz with 5% steps, supports multiple mobile-TV standards with sufficient margins for process and temperature variations. The filter also accomplishes a 30-dB variable gain range with 6-dB steps, and it relaxes the dynamic range requirement of a succeeding programmable gain amplifier. The power consumption of the filter, 3.4-5.0mW, is adjustable according to the bandwidth and the signal level. The filter was fabricated with on-chip bandwidth-calibration circuitry in 0.18-μm CMOS and occupied 0.81mm2.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Sensing Systems for Wireless Medicine (MediSense), Georgia Institute of Technology, Future Communication ICs Inc., Georgia Electronic Design Center
Contributors: Beck, S., Jeong, S., Min, S., Hwang, M. W., Kim, S. T., Lim, K., Tentzeris, E. M.
Number of pages: 4
Pages: 1328-1331
Publication date: Aug 2011
Peer-reviewed: Yes

Publication information

Journal: IEICE TRANSACTIONS ON ELECTRONICS
Volume: E94-C
Issue number: 8
ISSN (Print): 0916-8524
Ratings: 
  • Scopus rating (2011): CiteScore 0.55 SJR 0.233 SNIP 0.624
Original language: English
ASJC Scopus subject areas: Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials
Keywords: Active filters, Calibration, Receivers, Variable-gain amplifiers
Source: Scopus
Source ID: 79961033079

Research output: Contribution to journalArticleScientificpeer-review

A new power-consumption optimization technique for two-stage operational amplifiers

This paper proposes a technique for two-stage operational amplifiers (OPAMPs) to optimize power consumption according to various channel conditions of wireless communication systems. The proposed OPAMP has the ability of reducing the quiescent current of each stage independently by introducing additional common-mode feedback, therefore more optimization is possible according to the channel conditions than conventional two-stage OPAMPs. The simulations verify the benefits of the technique. As a proof-of-concept topology, the proposed OPAMPs were used in a channel-selection filter for a multi-standard mobile-TV receiver. The power consumption of the filter, 3.4-5.0mW, was adjustable according to the bandwidth, the noise, and the jammer level. The performance of the filter meets the requirements and verifies the effectiveness of the proposed approach. The filter was fabricated in 0.18-μm CMOS and occupied 0.64mm2.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Sensing Systems for Wireless Medicine (MediSense), Georgia Institute of Technology, Georgia Electronic Design Center
Contributors: Beck, S., Kim, S. T., Lee, M., Lim, K., Laskar, J., Tentzeris, M. M.
Number of pages: 3
Pages: 1138-1140
Publication date: Jun 2011
Peer-reviewed: Yes

Publication information

Journal: IEICE TRANSACTIONS ON ELECTRONICS
Volume: E94-C
Issue number: 6
ISSN (Print): 0916-8524
Ratings: 
  • Scopus rating (2011): CiteScore 0.55 SJR 0.233 SNIP 0.624
Original language: English
ASJC Scopus subject areas: Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials
Keywords: Active filters, Low-power consumption, Operational amplifier, Power optimization
Source: Scopus
Source ID: 79957937458

Research output: Contribution to journalArticleScientificpeer-review

Anisotropic and strain-dependent model of magnetostriction in electrical steel sheets

This paper presents an anisotropic and mechanical strain-dependent model of magnetostriction in electrical steel sheets and its application in finite-element computations. The presented model is bidirectional and the data needed for its derivation is extracted solely from unidirectional measurements under mechanical loading. The model has six parameters that describe the magnetic and strain behavior and two parameters that describe the anisotropy. The validation of the model is carried out through measurements and computations on a single-phase transformer-like device. The comparison between computation and measurement results seems to be reasonable regardless of the fact that the magnetic behavior is modeled as single valued, isotropic, and anhysteretic. Original magnetostriction measurements are also presented and the importance of magnetostriction anisotropy in a priori isotropic electrical steel sheets is demonstrated. The model is easy to implement in existing codes and the anisotropic behavior is straightforward to modify according to a specific material.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Smart Energy Systems (SES), Aalto University, Universiteit Gent, Ghent University, Zwijnaarde, Belgium
Contributors: Belahcen, A., Singh, D., Rasilo, P., Martin, F., Ghalamestani, S. G., Vandevelde, L.
Publication date: 1 Mar 2015
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Magnetics
Volume: 51
Issue number: 3
Article number: 2001204
ISSN (Print): 0018-9464
Ratings: 
  • Scopus rating (2015): CiteScore 1.77 SJR 0.575 SNIP 1.189
Original language: English
ASJC Scopus subject areas: Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials
Keywords: Anisotropy, magnetomechanical effects, magnetostriction, soft magnetic materials, transformers, vibrations
Source: Scopus
Source ID: 84928813895

Research output: Contribution to journalArticleScientificpeer-review

Segregation of iron losses from rotational field measurements and application to electrical machine

This paper presents a methodology for identifying a novel iron loss model and segregating the different loss components from measurements on a single-sheet tester with alternating and rotating fields. The eddy-current losses are first extracted with a 1-D numerical approach and the hysteresis and excess losses are then estimated with an analytical method that allows the separation of alternating and rotational hysteresis as well as excess losses. The elaborated iron loss model can be applied in case of distorted flux density and on a wide range of frequencies. The identified model is further applied in the time-stepping computation of an induction motor in the view of better estimation and segregation of iron losses. The results of no-load simulations at different voltage levels are in good agreement with the measured ones. All of the presented computations and models were validated experimentally.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Smart Energy Systems (SES), Aalto University
Contributors: Belahcen, A., Rasilo, P., Arkkio, A.
Publication date: Feb 2014
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Magnetics
Volume: 50
Issue number: 2
Article number: 7022104
ISSN (Print): 0018-9464
Ratings: 
  • Scopus rating (2014): CiteScore 1.68 SJR 0.696 SNIP 1.45
Original language: English
ASJC Scopus subject areas: Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials
Keywords: Electric machines, electromagnetic analysis, loss measurement, magnetic losses, magnetic materials
Source: Scopus
Source ID: 84900613868

Research output: Contribution to journalArticleScientificpeer-review

Advancements in Solution Processable Devices using Metal Oxides For Printed Internet-of-Things Objects

Internet-of-things (IoT) objects are expected to exceed 75 billion objects by 2020, and a large part of the expansion is expected to be at a finer granularity than existing silicon-based IoT objects (i.e. tablets and cell phones) can deliver [1]. Currently, placing a room light or a thermostat on the internet for remote control is considered progressive. However, if printed electronics can achieve performance increases, then IoT objects could be affixed to almost anything, such as coffee creamer cartons, cereal boxes, or that missing sock. Each of these IoT objects could be driving a sensor, perhaps position, temperature or pressure, essentially a multitude of applications. In order for IoT objects to emulate a simple postage stamp, with self-powering from energy scavenging and local energy storage, all housed in a non-toxic flexible form factor, advances in solution processable devices need to occur.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Electrical Engineering, Ohio State University, Wayne State University
Contributors: Berger, P. R., Li, M., Mattei, R. M., Niang, M. A., Talisa, N., Tripepi, M., Harris, B., Bhalerao, S. R., Chowdhury, E. A., Winter, C. H., Lupo, D.
Number of pages: 3
Pages: 160-162
Publication date: 1 Mar 2019

Host publication information

Title of host publication: 2019 Electron Devices Technology and Manufacturing Conference, EDTM 2019
Publisher: IEEE
ISBN (Electronic): 9781538665084
ASJC Scopus subject areas: Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Instrumentation, Hardware and Architecture
Keywords: ALD, CMOS and SOI, energy scavenging, IoT, low-power electronics, Manufacturing, NDR, tunnel diodes

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Construction of an Interconnected Nanostructured Carbon Black Network: Development of Highly Stretchable and Robust Elastomeric Conductors

In the present work, a strong filler-filler network of conductive carbon black was strategically established in an elastomer matrix, which leads to a unique combination of electrical and mechanical properties. The novelty of our composites was the development of a strong percolated morphology of nanostructured conducting carbon black particles by the incorporation of relatively large nonreinforcing spherical silica particles, inside the soft elastomer matrix. This technique allowed us to fabricate solution styrene butadiene rubber (S-SBR) composites with outstanding electrical conductivity of 40 S/m, tensile strength ∼10 MPa, and extensibility up to 200%. Furthermore, the electrical conductivity was strain-independent up to 50% elongation strain. The electrical conductivity was found to be unaltered after 2000 loading-unloading cycles. This is the first ever report of a robust elastomeric system with such high electrical conductivity where all the basic ingredients used were selected from well-known commercially available raw materials of rubber industry. This work directly manifests an industrially viable method for preparing high-performance elastic conductors that can be utilized in robust and flexible applications.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Materials Science, Engineering materials science and solutions (EMASS), Leibniz-Institut für Polymerforschung Dresden E.V., Technische Universität Dresden, Institut für Werkstoffwissenschaft, Institut für Polymerwerkstoffe E.V., Elkem AS, Silicon Materials
Contributors: Bhagavatheswaran, E. S., Parsekar, M., Das, A., Le, H. H., Wiessner, S., Stöckelhuber, K. W., Schmaucks, G., Heinrich, G.
Number of pages: 9
Pages: 21723-21731
Publication date: 17 Sep 2015
Peer-reviewed: Yes

Publication information

Journal: Journal of Physical Chemistry C
Volume: 119
Issue number: 37
ISSN (Print): 1932-7447
Ratings: 
  • Scopus rating (2015): CiteScore 4.68 SJR 1.886 SNIP 1.246
Original language: English
ASJC Scopus subject areas: Physical and Theoretical Chemistry, Electronic, Optical and Magnetic Materials, Surfaces, Coatings and Films, Energy(all)
Source: Scopus
Source ID: 84941928016

Research output: Contribution to journalArticleScientificpeer-review

0.6V threshold voltage thin film transistors with solution processable indium oxide (In2O3) Channel and Anodized High-κ Al2O3 Dielectric

Low-voltage operation and low processing temperature of metal oxide transistors remain a challenge. Commonly metal oxide transistors are fabricated at very high processing temperatures (above 500°C) and their operating voltage is quite high (30-50 V). Here, thin-film transistors (TFT) are reported based upon solution processable indium oxide (In2O3) and room temperature processed anodized high- κ aluminum oxide (Al2O3) for gate dielectrics. The In2O3 TFTs operate well below the drain bias (Vds) of 3.0 V, with on/off ratio 105, subthreshold swing (SS) 160 mV/dec, hysteresis 0.19 V, and low threshold voltage (Vth)~0.6 V. The electron mobility (μ) is as high as 3.53 cm2/V.s in the saturation regime and normalized transconductance (gm) is 75μS/mm. In addition, the detailed capacitance-voltage (C-V) analysis to determine interface trap states density was also investigated. The interface trap density (Dit) in the oxide/semiconductor interface was quite low, i.e., 0.99 × 1011 - 2.98 × 1011 eV-1· cm2, signifying acceptable compatibility of In2O3 with anodic Al2O3.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Electrical Engineering, Columbia University in the City of New York, VTT Technical Research Centre of Finland, Department of Electrical and Computer Engineering, Ohio State University
Contributors: Bhalerao, S. R., Lupo, D., Zangiabadi, A., Kymissis, I., Leppäniemi, J., Alastalo, A., Berger, P. R.
Number of pages: 4
Pages: 1112-1115
Publication date: 1 Jul 2019
Peer-reviewed: Yes

Publication information

Journal: IEEE Electron Device Letters
Volume: 40
Issue number: 7
ISSN (Print): 0741-3106
Ratings: 
  • Scopus rating (2019): SJR 1.397 SNIP 1.633
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Electrical and Electronic Engineering
Keywords: anodization, indium oxide (InO), interface state density, low voltage, Metal oxide semiconductors, solution processing, TFT
Source: Scopus
Source ID: 85068181785

Research output: Contribution to journalArticleScientificpeer-review

Investigating solvent effects on aggregation behaviour, linear and nonlinear optical properties of silver nanoclusters

We herein report the solvent effects on the aggregation, linear and nonlinear optical properties of silver nanoclusters synthesised using three solvents namely; ethanol, acetone and isopropanol. The Ag clusters were characterized using UV–Visible (UV–vis) and photoluminescence (PL) spectroscopy, Fourier transform-infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy (HRTEM), small angle X-ray scattering (SAXS), dynamic light scattering (DLS), and open aperture Z-Scan measurements. Density functional theory (DFT) calculations at the B3PW91 level of theory, were done to compute the electric dipole, quadrupole, octapole and hexadecapole moment of mercaptosuccinic acid and mercaptosuccinic acid-Ag9 cluster in three solvents. Linear optical properties show characteristic absorption profile with quantum confinement at different wavelengths for all the three clusters. The Open aperture Z-scan measurement in Ag clusters establishes the optical limiting properties which arise mostly from excited state absorption (ESA) and relatively weak saturable absorption (SA). The nonlinear optical behaviour varies within the three clusters with maximum optical limiting value obtained for the clusters synthesised using acetone. The theoretically computed hyperpolarizabilities together with z-scan measurements establish the solvent effect on the clusters and their potential applications in optical limiting devices.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Photonics, St Teresas’s College, Mahatma Gandhi University, Kolkata Centre, Birla Institute of Technology & Science, Swinburne University of Technology, University of Johannesburg
Contributors: Bhavitha, K. B., Nair, A. K., Perumbilavil, S., Joseph, S., Kala, M. S., Saha, A., Narayanan, R. A., Hameed, N., Thomas, S., Oluwafemi, O. S., Kalarikkal, N.
Number of pages: 11
Pages: 695-705
Publication date: 1 Nov 2017
Peer-reviewed: Yes

Publication information

Journal: Optical Materials
Volume: 73
ISSN (Print): 0925-3467
Ratings: 
  • Scopus rating (2017): CiteScore 2.38 SJR 0.592 SNIP 1.054
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Computer Science(all), Atomic and Molecular Physics, and Optics, Electrical and Electronic Engineering
Keywords: Aggregation behaviour, DFT, Linear optical properties, Non linear optical properties, Silver nanoclusters, Solvent effects
Source: Scopus
Source ID: 85030173026

Research output: Contribution to journalArticleScientificpeer-review

Sub-microwatt direct laser writing of fluorescent gold nanoclusters in polymer films

We report on the micro-pattering of fluorescent gold nanoclusters embedded in polyvinyl alcohol film using a low-cost continuous-wave laser. We show that the formation of gold nanoclusters requires low-level laser irradiation (<100 W/cm2), corresponding to a sub-microwatt focused beam. This low-intensity requirement enables substantially higher speed and cost-effective light patterning process. As a result of using only small intensities during gold nanoclusters production, no microscopic topological changes were observed in the polymer film. This class of gold nanoclusters potentially finds application in high-speed authenticity marking and similar labeling applications.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Physics, Research group: Applied Optics
Contributors: Bitarafan, M. H., Suomala, S., Toivonen, J.
Number of pages: 11
Pages: 138-148
Publication date: 2020
Peer-reviewed: Yes

Publication information

Journal: Optical Materials Express
Volume: 10
Issue number: 1
ISSN (Print): 2159-3930
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials

Bibliographical note

INT=phys,"Bitarafan, Mohammad H."
INT=phys,"Suomala, Sofia"

Source: Scopus
Source ID: 85079045790

Research output: Contribution to journalArticleScientificpeer-review

Nanoparticles in optical waveguides: A toolbox to promote lasers, amplifiers and sensors

The success of glass photonics are many, with a large spectrum of applications covering Information and Communication Technology, Health and Biology, Structural Engineering, and Environment Monitoring Systems, etc. A paradigmatic example is the development of the Erbium-Doped Fiber Amplifier (EDFA) allowing the raise of optical telecommunications and high speed internet. Silica glass is the most common glass used for photonics applications. However, certain of its characteristics may be detrimental for luminescence properties (low rare-earth solubility, high phonon energy, etc). To overcome these limitations, the use of nanoparticles in optical waveguides has gained large interest in modern photonic technology nowadays. Such waveguides would combine the advantages of silica (transparency, cost, chemical and mechanical durability, etc.) and the specific properties provided by the nanoparticles which encapsulate the rare-earth ions. In this paper, we discuss on the opportunities offered by the nanoparticles addition in glasses for lasers and amplifiers thanks to the engineering of the spectroscopic properties. We present also an emerging application: sensors based on high scattered fibers.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Physics, Research group: Photonics Glasses, Université Côte d'Azur, Ecole Centrale de Nantes, Academy of Sciences, UPRES EA 4464, University of Montpellier, CSMFO Lab., Enrico Fermi Centre
Contributors: Blanc, W., Vermillac, M., Petit, L., Lukowiak, A., Lu, Z., Mady, F., Benabdesselam, M., Chaussedent, S., Mehdi, A., Ferrari, M.
Publication date: 1 Jul 2019

Host publication information

Title of host publication: 21st International Conference on Transparent Optical Networks, ICTON 2019
Publisher: IEEE
ISBN (Electronic): 9781728127798

Publication series

Name: International Conference on Transparent Optical Networks
ISSN (Electronic): 2161-2064
ASJC Scopus subject areas: Computer Networks and Communications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials
Keywords: Amplifiers, Glass, Lasers, Nanoparticles, Sensors, Waveguides

Bibliographical note

jufoid=72297

Source: Scopus
Source ID: 85073052623

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

1.3 μm InAs quantum dot semiconductor disk laser

Vertical-external-cavity surface-emitting lasers (VECSEL), or semiconductor disk lasers (SDL), are attractive laser source for a wide range of applications owing to unique possibility to combine high output power with an excellent beam quality [1]. The intrinsic features of InAs quantum dots (QD) can offer low threshold, broad wavelength tunability, fast carrier dynamics and low temperature sensitivity. Recently, continuous wave (CW) operation of QD-based VECSEL emitting at 1.25 μm with output powers reaching multi-watt levels were achieved at room temperature [2]. However, extending the emission wavelength to 1.3 μm and beyond becomes more challenging. To date, QD-based VECSEL with optical power greater than 0.5 mW at 1305 nm has been demonstrated [3]. Here, we present a record-high power InAs/InGaAs QD-based VECSEL operating at the wavelength of 1.3 μm.

General information

Publication status: Published
Organisations: Optoelectronics Research Centre, Research group: Ultrafast and intense lasers, Ioffe Physico-Technical Institute, Peter the Great St. Petersburg Polytechnic University
Contributors: Blokhin, S. A., Bobrov, M. A., Blokhin, A. A., Kuzmenkov, A. G., Vasil'Ev, A. P., Maleev, N. A., Dudelev, V. V., Soboleva, K. K., Sokolovskii, G. S., Rantamäki, A., Okhotnikov, O., Ustinov, V. M.
Pages: R317
Publication date: 23 Aug 2016
Peer-reviewed: Unknown
Event: Paper presented at 2016 International Conference Laser Optics, LO 2016, St. Petersburg, Russian Federation.
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Atomic and Molecular Physics, and Optics
Source: Scopus
Source ID: 84987923895

Research output: Other conference contributionPaper, poster or abstractScientific

Soft graphoepitaxy for large area directed self-assembly of polystyrene-block-poly(dimethylsiloxane) block copolymer on nanopatterned poss substrates fabricated by nanoimprint lithography

Polyhedral oligomeric silsequioxane (POSS) derivatives have been successfully employed as substrates for graphoepitaxial directed self-assembly (DSA) of block copolymers (BCPs). Tailored POSS materials of tuned surface chemistry are subject to nanoimprint lithography (NIL) resulting in topographically patterned substrates with dimensions commensurate with the BCP block length. A cylinder forming polystyrene-block-polydimethylsiloxane (PS-b-PDMS) BCP is synthesized by sequential living anionic polymerization of styrene and hexamethylcyclotrisiloxane. The patterned POSS materials provide a surface chemistry and topography for DSA of this BCP and after solvent annealing the BCP shows well-ordered microphase segregation. The orientation of the PDMS cylinders to the substrate plane could be controlled within the trench walls by the choice of the POSS materials. The BCP patterns are successfully used as on-chip etch mask to transfer the pattern to underlying silicon substrate. This soft graphoepitaxy method shows highly promising results as a means to generate lithographic quality patterns by nonconventional methods and could be applied to both hard and soft substrates. The methodology might have application in several fields including device and interconnect fabrication, nanoimprint lithography stamp production, nanofluidic devices, lab-on-chip, or in other technologies requiring simple nanodimensional patterns. A methodology for fabricating highly ordered silicon nanostructures at a substrate is reported using nanoimprint lithography imprinted polyhedral oligomeric silsequioxane (POSS) substrates for graphoepitaxial directed self-assembly (DSA) of block copolymer (BCP). The patterned POSS materials provide a surface chemistry and topography for DSA of a cylinder forming polystyrene-block-polydimethylsiloxane BCP with well-ordered microphase segregation upon solvent annealing.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Frontier Photonics, Trinity College Dublin, University College Cork, Tyndall National Institute at National University of Ireland, Cork, Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Laboratoire des Technologies de la Microelectronique (CNRS), Profactor GmbH, University Campus-Dourouti
Contributors: Borah, D., Rasappa, S., Salaun, M., Zellsman, M., Lorret, O., Liontos, G., Ntetsikas, K., Avgeropoulos, A., Morris, M. A.
Number of pages: 8
Pages: 3425-3432
Publication date: 1 Jun 2015
Peer-reviewed: Yes

Publication information

Journal: Advanced Functional Materials
Volume: 25
Issue number: 22
ISSN (Print): 1616-301X
Ratings: 
  • Scopus rating (2015): CiteScore 11.93 SJR 4.859 SNIP 2.439
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Biomaterials, Condensed Matter Physics, Electrochemistry
Keywords: block copolymer, directed self-assembly, nanoimprint lithography, pattern transfer, polyhedral oligomeric silsequioxane (POSS)
Source: Scopus
Source ID: 84930932614

Research output: Contribution to journalArticleScientificpeer-review

The sensitivity of random polymer brush-lamellar polystyrene-b-polymethylmethacrylate block copolymer systems to process conditions

The use of random copolymer brushes (polystyrene- r-polymethylmethacrylate - PS- r-PMMA) to 'neutralise' substrate surfaces and ordain perpendicular orientation of the microphase separated lamellae in symmetric polystyrene- b-polymethylmethacrylate (PS- b-PMMA) block copolymers (BCPs) is well known. However, less well known is how the brushes interact with both the substrate and the BCP, and how this might change during thermal processing. A detailed study of changes in these films for different brush and diblock PS- b-PMMA molecular weights is reported here. In general, self-assembly and pattern formation is altered little, and a range of brush molecular weights are seen to be effective. However, on extended anneal times, the microphase separated films can undergo dimension changes and loss of order. This process is not related to any complex microphase separation dynamics but rather a degradation of methacrylate components in the film. The data suggest that care must be taken in interpretation of structural changes in these systems as being due to BCP only effects.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Frontier Photonics, Tyndall National Institute at National University of Ireland, Cork, Materials Chemistry and Analysis Group, University College Cork, Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Leixlip Co.
Contributors: Borah, D., Rasappa, S., Senthamaraikannan, R., Shaw, M. T., Holmes, J. D., Morris, M. A.
Number of pages: 11
Pages: 192-202
Publication date: 1 Mar 2013
Peer-reviewed: Yes

Publication information

Journal: Journal of Colloid and Interface Science
Volume: 393
Issue number: 1
ISSN (Print): 0021-9797
Ratings: 
  • Scopus rating (2013): CiteScore 3.73 SJR 1.195 SNIP 1.437
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Biomaterials, Surfaces, Coatings and Films, Colloid and Surface Chemistry
Keywords: Microphase separation, Polymer brush, Polystyrene-b-polymethylmethacrylate, Polystyrene-r-polymethylmethacrylate, Surface morphology
Source: Scopus
Source ID: 84873060382

Research output: Contribution to journalArticleScientificpeer-review

Plasma etch technologies for the development of ultra-small feature size transistor devices

The advances in information and communication technologies have been largely predicated around the increases in computer processor power derived from the constant miniaturization (and consequent higher density) of individual transistors. Transistor design has been largely unchanged for many years and progress has been around scaling of the basic CMOS device. Scaling has been enabled by photolithography improvements (i.e. patterning) and secondary processing such as deposition, implantation, planarization, etc. Perhaps the most important of the secondary processes is the plasma etch methodology whereby the pattern created by lithography is 'transferred' to the surface via a selective etch to remove exposed material. However, plasma etch technologies face challenges as scaling continues. Maintaining absolute fidelity in pattern transfer at sub-16 nm dimensions will require advances in plasma technology (plasma sources, chamber design, etc) and chemistry (etch gases, flows, interactions with substrates, etc). In this paper, we illustrate some of these challenges by discussing the formation of ultra-small device structures from the directed self-assembly of block copolymers (BCPs) where nanopatterns are formed from the micro-phase separation of the system. The polymer pattern is transferred by a double etch procedure where one block is selectively removed and the remaining block acts as a resist pattern for silicon pattern transfer. Data are presented which shows that highly regular nanowire patterns of feature size below 20 nm can be created using etch optimization techniques and in this paper we demonstrate generation of crystalline silicon nanowire arrays with feature sizes below 8 nm. BCP techniques are demonstrated to be applicable from these ultra-small feature sizes to 40 nm dimensions. Etch profiles show rounding effects because etch selectivity in these nanoscale resist patterns is limited and the resist thickness rather low. The nanoscale nature of the topography generated also places high demands on developing new etch processes.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Frontier Photonics, Trinity College Dublin, University College Cork
Contributors: Borah, D., Shaw, M. T., Rasappa, S., Farrell, R. A., O'Mahony, C., Faulkner, C. M., Bosea, M., Gleeson, P., Holmes, J. D., Morris, M. A.
Publication date: 4 May 2011
Peer-reviewed: Yes

Publication information

Journal: Journal of Physics D: Applied Physics
Volume: 44
Issue number: 17
Article number: 174012
ISSN (Print): 0022-3727
Ratings: 
  • Scopus rating (2011): CiteScore 2.36 SJR 1.266 SNIP 1.424
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Acoustics and Ultrasonics, Surfaces, Coatings and Films
Source: Scopus
Source ID: 79954607730

Research output: Contribution to journalArticleScientificpeer-review

Pipeline for effective denoising of digital mammography and digital breast tomosynthesis

Denoising can be used as a tool to enhance image quality and enforce low radiation doses in X-ray medical imaging. The effectiveness of denoising techniques relies on the validity of the underlying noise model. In full-field digital mammography (FFDM) and digital breast tomosynthesis (DBT), calibration steps like the detector offset and flat-fielding can affect some assumptions made by most denoising techniques. Furthermore, quantum noise found in X-ray images is signal-dependent and can only be treated by specific filters. In this work we propose a pipeline for FFDM and DBT image denoising that considers the calibration steps and simplifies the modeling of the noise statistics through variance-stabilizing transformations (VST). The performance of a state-of-the-art denoising method was tested with and without the proposed pipeline. To evaluate the method, objective metrics such as the normalized root mean square error (N-RMSE), noise power spectrum, modulation transfer function (MTF) and the frequency signal-to-noise ratio (SNR) were analyzed. Preliminary tests show that the pipeline improves denoising. When the pipeline is not used, bright pixels of the denoised image are under-filtered and dark pixels are over-smoothed due to the assumption of a signal-independent Gaussian model. The pipeline improved denoising up to 20% in terms of spatial N-RMSE and up to 15% in terms of frequency SNR. Besides improving the denoising, the pipeline does not increase signal smoothing significantly, as shown by the MTF. Thus, the proposed pipeline can be used with state-of-the-art denoising techniques to improve the quality of DBT and FFDM images.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Signal Processing, University of São Paulo, University of Pennsylvania
Contributors: Borges, L. R., Bakic, P. R., Foi, A., Maidment, A. D., Vieira, M. A.
Publication date: 2017

Host publication information

Title of host publication: Medical Imaging 2017 : Physics of Medical Imaging
Publisher: SPIE
Article number: 1013206
ISBN (Electronic): 9781510607095

Publication series

Name: Progress in biomedical optics and imaging
ISSN (Electronic): 1605-7422
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Atomic and Molecular Physics, and Optics, Biomaterials, Radiology Nuclear Medicine and imaging
Keywords: Denoising, Digital breast tomosynthesis, Full field digital mammography, Variance stabilization
Electronic versions: 

Bibliographical note

jufoid=65546

Source: Scopus
Source ID: 85020415748

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Strand and cable R&D for fast cycled magnets at CERN

Fast cycled superconducting magnets (FCM's) are an option of interest for the long-term consolidation and upgrade plan of the LHC accelerator complex. In the past two years we have conducted an R&D targeted at investigating the feasibility, operational issues and economical advantage of FCM's in the range of 2 T bore field, continuously cycled at 1 Hz. In this paper we report the main results on the development of strands and cables suitable for this application, providing details on the strands tested and the cable manufacturing and performance.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: European Organization for Nuclear Research, BNG, Lawrence Berkeley National Laboratory
Contributors: Bottura, L., Bonasia, A., Borgnolutti, F., Gaertner, W., Le Naour, S., Oberli, L., Peiro, G., Richter, D., Salmi, T., Sikler, G., Willering, G.
Number of pages: 5
Pages: 2354-2358
Publication date: Jun 2011
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Applied Superconductivity
Volume: 21
Issue number: 3 PART 2
ISSN (Print): 1051-8223
Ratings: 
  • Scopus rating (2011): CiteScore 1.16 SJR 0.368 SNIP 1.062
Original language: English
ASJC Scopus subject areas: Electrical and Electronic Engineering, Condensed Matter Physics, Electronic, Optical and Magnetic Materials
Keywords: AC loss, Superconducting accelerator magnets, Superconducting cables, Superconducting filaments and wires
Source: Scopus
Source ID: 79957900922

Research output: Contribution to journalArticleScientificpeer-review

Influence of the P2O5/Al2O3 co-doping on the local environment of erbium ions and on the 1.5 μm quantum efficiency of Er3+-borosilicate glasses

In this paper, the absorption properties of Er3+-doped borosilicate glasses with various P2O5 and Al 2O3 content are measured for different silica concentrations. The Judd-Ofelt parameters (Ω2, Ω4 and Ω6) have been calculated in order to investigate the local environment of the rare-earth cations. The compositional changes of Ω2 and Ω6 are attributed to changes in the bonding between Er3+ and surrounding ligand groups due to structural modifications occurring with the introduction of P2O 5 and Al2O3. The luminescence quantum efficiency of the 4I13/24I 15/2 transition slightly increases with the addition of P 2O5 whereas it decreases with the progressive replacement of P2O5 by Al2O3. We noticed that it also increases when the silica content is higher.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Frontier Photonics, Politecnico di Torino, nLIGHT Corporation, Johan Gadolin Process Chemistry Centre, Abo Akademi University
Contributors: Bourhis, K., Boetti, N. G., Koponen, J., Milanese, D., Petit, L.
Number of pages: 6
Pages: 926-931
Publication date: Mar 2014
Peer-reviewed: Yes

Publication information

Journal: Optical Materials
Volume: 36
Issue number: 5
ISSN (Print): 0925-3467
Ratings: 
  • Scopus rating (2014): CiteScore 2.24 SJR 0.721 SNIP 1.204
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Electrical and Electronic Engineering, Atomic and Molecular Physics, and Optics, Computer Science(all)
Keywords: Er doped borosilicate glasses, Judd-Ofelt parameters, Lifetime, Luminescence quantum efficiency
Source: Scopus
Source ID: 84893847084

Research output: Contribution to journalArticleScientificpeer-review

High-dimensional quantum gates using full-field spatial modes of photons

Unitary transformations are the fundamental building blocks of gates and operations in quantum information processing, allowing the complete manipulation of quantum systems in a coherent manner. In the case of photons, optical elements that can perform unitary transformations are readily available only for some degrees of freedom, e.g., wave plates for polarization. However, for high-dimensional states encoded in the transverse spatial modes of light, performing arbitrary unitary transformations remains a challenging task for both theoretical proposals and actual implementations. Following the idea of multi-plane light conversion, we show that it is possible to perform a broad variety of unitary operations at high quality by using only a few phase modulation planes. More importantly, we experimentally implement several high-dimensional quantum gates for up to five-dimensional states encoded in the full-field mode structure of photons. In particular, we realize cyclic and quantum Fourier transformations, known as Pauli X -gates and Hadamard Ĥ-gates, respectively, with an average visibility of more than 90%. In addition, we demonstrate near-perfect “unitarity” by means of quantum process tomography, unveiling a process purity of 99%. Last, we demonstrate the benefit of the two independent spatial degrees of freedom, i.e., azimuthal and radial, and implement a two-qubit controlled-NOT quantum operation on a single photon. Thus, our demonstrations open up new paths to implement high-dimensional quantum operations, which can be applied to various tasks in quantum communication, computation, and sensing schemes.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Physics, Austrian Academy of Sciences, University of Ottawa, Canada
Contributors: Brandt, F., Hiekkamäki, M., Bouchard, F., Huber, M., Fickler, R.
Number of pages: 10
Pages: 98-107
Publication date: 20 Feb 2020
Peer-reviewed: Yes

Publication information

Journal: Optica
Volume: 7
Issue number: 2
ISSN (Print): 2334-2536
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Atomic and Molecular Physics, and Optics
Source: Scopus
Source ID: 85079614867

Research output: Contribution to journalArticleScientificpeer-review

Designing materials with desired electromagnetic properties

In this work, we suggest and demonstrate a robust method to tune the plasma frequencies of wire mediums. The method we suggest involves the use of two or more wire arrangements in the unit cell. By incorporating the method we suggested it is possible to tune the plasma frequencies of wire mediums effectively by use of lower metal densities. In addition, we study the effective permittivities and permeabilities of labyrinth based metamaterials. Our results show that the effective permeability of the labyrinth based metamaterial medium is negative above a certain frequency. The results of the effective permittivity calculations for the labyrinth based metamaterial medium reveal that the labyrinth structure exhibits a strong dielectric response near the magnetic resonance frequency. Finally, we design labyrinth based left-handed mediums that have several desired properties such as simultaneous μ, ε = -1 and μ, ε = 0.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Bilkent University, Nanotechnology Research Center
Contributors: Bulu, I., Caglayan, H., Ozbay, E.
Number of pages: 5
Pages: 2611-2615
Publication date: Dec 2006
Peer-reviewed: Yes

Publication information

Journal: Microwave and Optical Technology Letters
Volume: 48
Issue number: 12
ISSN (Print): 0895-2477
Ratings: 
  • Scopus rating (2006): SJR 0.564 SNIP 0.685
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Atomic and Molecular Physics, and Optics, Condensed Matter Physics, Electrical and Electronic Engineering
Keywords: Effective medium, Metamaterials, Negative index, Split ring

Bibliographical note

EXT="Caglayan, Humeyra"

Source: Scopus
Source ID: 33750556414

Research output: Contribution to journalArticleScientificpeer-review

Radiation properties of sources inside photonic crystals

In this work, we have experimentally studied the emission of radiation from a monopole source embedded in a photonic crystal. We have demonstrated the enhancement of radiation at the band edges and at the cavity modes including coupled cavity modes. Moreover, we have shown that the emission of radiation from a source depends on the group velocities of the modes and on the electric field intensities of the modes at the source location.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Bilkent University
Contributors: Bulu, I., Caglayan, H., Ozbay, E.
Publication date: 15 May 2003
Peer-reviewed: Yes

Publication information

Journal: Physical Review B - Condensed Matter and Materials Physics
Volume: 67
Issue number: 20
ISSN (Print): 1098-0121
Ratings: 
  • Scopus rating (2003): SJR 2.184 SNIP 1.245
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics

Bibliographical note

EXT="Caglayan, Humeyra"

Source: Scopus
Source ID: 0037826783

Research output: Contribution to journalArticleScientificpeer-review

Parametric conversion in micrometer and submicrometer structured ferroelectric crystals by surface poling

We report on recent technological improvements concerning nonlinear patterning of lithium niobate and lithium tantalate in the micrometer and submicrometer scales using surface periodic poling for ferroelectric domain inversion. The fabricated samples were employed for frequency doubling via quasiphase-matching both in bulk and guided wave geometries, including forward and backward configurations and wavelength conversion in bands C and L. We also investigated short-period quasiperiodic samples with randomly distributed mark-to-space ratios.

General information

Publication status: Published
MoE publication type: A2 Review article in a scientific journal
Organisations: Frontier Photonics, Building No. 9, Nonlinear Optics and OptoElectronics Lab, University “Roma Tre”
Contributors: Busacca, A. C., Stivala, S., Curcio, L., Assanto, G.
Publication date: 2012
Peer-reviewed: Yes

Publication information

Journal: International Journal of Optics
Volume: 2012
Article number: 606892
ISSN (Print): 1687-9384
Ratings: 
  • Scopus rating (2012): CiteScore 0.33 SJR 0.184 SNIP 0.437
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Atomic and Molecular Physics, and Optics
Source: Scopus
Source ID: 84858185701

Research output: Contribution to journalReview ArticleScientificpeer-review

Observation of cavity structures in composite metamaterials

We investigated the cavity structure by the deformation of a unit cell of a Composite Metamaterial (CMM) structure. We considered different cavity structures with different resonance frequencies and Q-factors. We observed the Q-factor of the cavity resonance as 108 for a CMM based single cavity wherein the cavity structure is a closed ring structure. We investigated the reduced photon lifetime and observed that at the cavity resonance, the effective group velocity was reduced by a factor of 20 for a CMM based single cavity compared to the electromagnetic waves propagating in free space. Since the unit cells of metamaterials are much smaller than the operation wavelength, subwavelength localization is possible within these metamaterial cavity structures. We found that the electromagnetic field is localized into a region of/8, where is the cavity resonance wavelength. Subsequently, we brought two cavities together with an intercavity distance of two metamaterial unit cells and then investigated the transmission spectrum of CMM based interacting 2-cavity system. Finally, using the tight-binding picture we observed the normalized group velocity corresponding to the coupled cavity structure.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Nanotechnology Research Center, Bilkent University
Contributors: Caglayan, H., Özbay, E.
Publication date: 2010
Peer-reviewed: Yes

Publication information

Journal: Journal of Nanophotonics
Volume: 4
Issue number: 1
Article number: 041790
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Keywords: cavity, coupled cavity, localization, metamaterials

Bibliographical note

EXT="Caglayan, Humeyra"

Source: Scopus
Source ID: 80455156087

Research output: Contribution to journalArticleScientificpeer-review

The magical world of metamaterials

We review experimental and theoretical studies performed on left-handed metamaterials (LHM). The metamaterials exhibit quiet unusual electromagnetic properties such as negative refraction, negative phase velocity, subwavelength focusing, subwavelength cavities and enhanced transmission.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Nanotechnology Research Center, Bilkent University
Contributors: Caglayan, H., Ozbay, E.
Publication date: 2009

Host publication information

Title of host publication: Photonic Materials, Devices, and Applications III
Volume: 7366
Article number: 73660X
ISBN (Print): 9780819476401

Publication series

Name: Proceedings of SPIE
Publisher: SPIE
Volume: 7366
ISSN (Print): 0277-786X
ISSN (Electronic): 1996-756X
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Computer Science Applications, Applied Mathematics, Electrical and Electronic Engineering
Keywords: Left-handed metamaterial, Metamaterials, Negative refractive index, Superlens

Bibliographical note

EXT="Caglayan, Humeyra"

Source: Scopus
Source ID: 70349983117

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Observation of off-axis directional beaming via subwavelength asymmetric metallic gratings

It is possible to obtain enhanced and directional beams using subwavelength metallic structures. However, the enhanced beams throughout such structures are only directed towards the propagation direction. In this study, we design the output surface gratings asymmetrically in order to steer the beaming angle. We use a metallic structure with a subwavelength slit (λ/10) and grating periods of 14 mm and 22 mm on different sides of the output surface. We demonstrate off-axis directional beaming in the microwave regime with an FWHM of 10° with a beaming angle of 15°. The beaming angle can be changed by arranging the grating periods of the output surface of the metallic structure.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Bilkent University, Harvard University
Contributors: Caglayan, H., Bulu, I., Ozbay, E.
Publication date: 2009
Peer-reviewed: Yes

Publication information

Journal: Journal of Physics D: Applied Physics
Volume: 42
Issue number: 4
Article number: 045105
ISSN (Print): 0022-3727
Ratings: 
  • Scopus rating (2009): SJR 1.269 SNIP 1.326
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Surfaces, Coatings and Films, Acoustics and Ultrasonics, Condensed Matter Physics

Bibliographical note

EXT="Caglayan, H."

Source: Scopus
Source ID: 67650075571

Research output: Contribution to journalArticleScientificpeer-review

Cavity formation in split ring resonators

We report that it is possible to obtain a cavity structure by the deformation of a unit cell of an split ring resonator (SRR) structure. We presented the Q-factor of the cavity resonance as 192 for an SRR-based single cavity. Subsequently, we brought two and three cavities together with an intercavity distance of two metamaterial unit cells and investigated the transmission spectrum of SRR-based interacting 2-cavity and 3-cavity systems. The splitting of eigenmodes due to the interaction between the localized electromagnetic cavity modes was observed. Eventually, in taking full advantage of the effective medium theory, we modeled SRR-based cavities as 1D Fabry-Perot reflectors (FPRs) with a subwavelength cavity at the center. Finally, we observed that at the cavity resonance, the effective group velocity was reduced by a factor of 67 for an SRR-based single cavity compared to the electromagnetic waves propagating in free space.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Nanotechnology Research Center, Harvard University
Contributors: Caglayan, H., Bulu, I., Loncar, M., Ozbay, E.
Number of pages: 5
Pages: 200-204
Publication date: Dec 2008
Peer-reviewed: Yes

Publication information

Journal: Photonics and Nanostructures - Fundamentals and Applications
Volume: 6
Issue number: 3-4
ISSN (Print): 1569-4410
Ratings: 
  • Scopus rating (2008): SJR 1.212 SNIP 1.169
Original language: English
ASJC Scopus subject areas: Electrical and Electronic Engineering, Hardware and Architecture, Condensed Matter Physics, Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials
Keywords: Cavity, Metamaterials, Split rind resonator

Bibliographical note

EXT="Caglayan, Humeyra"

Source: Scopus
Source ID: 56049112536

Research output: Contribution to journalArticleScientificpeer-review

Directional selectivity through the subwavelength slit in metallic gratings

An approach for obtaining strong directional selectivity through a single subwavelength slit in non-symmetric metallic gratings is shown theoretically and experimentally. Directionality effect originates from the different resonance frequencies of two interfaces.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Bilkent University, Nanotechnology Research Center
Contributors: Cakmakyapan, S., Caglayan, H., Serebryannikov, A., Ozbay, E.
Publication date: 2011

Host publication information

Title of host publication: 2011 Conference on Lasers and Electro-Optics : Laser Science to Photonic Applications, CLEO 2011
Article number: 5951099
ISBN (Print): 9781557529107
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Atomic and Molecular Physics, and Optics

Bibliographical note

EXT="Caglayan, Humeyra"

Source: Scopus
Source ID: 80052115222

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Light-trapping enhanced thin-film III-V quantum dot solar cells fabricated by epitaxial lift-off

We report thin-film InAs/GaAs quantum dot (QD) solar cells with n-i-p+ deep junction structure and planar back reflector fabricated by epitaxial lift-off (ELO) of full 3-in wafers. External quantum efficiency measurements demonstrate twofold enhancement of the QD photocurrent in the ELO QD cell compared to the wafer-based QD cell. In the GaAs wavelength range, the ELO QD cell perfectly preserves the current collection efficiency of the baseline single-junction ELO cell. We demonstrate by full-wave optical simulations that integrating a micro-patterned diffraction grating in the ELO cell rearside provides more than tenfold enhancement of the near-infrared light harvesting by QDs. Experimental results are thoroughly discussed with the help of physics-based simulations to single out the impact of QD dynamics and defects on the cell photovoltaic behavior. It is demonstrated that non radiative recombination in the QD stack is the bottleneck for the open circuit voltage (Voc) of the reported devices. More important, our theoretical calculations demonstrate that the Voc offset of 0.3. V from the QD ground state identified by Tanabe et al., 2012, from a collection of experimental data of high quality III-V QD solar cells is a reliable - albeit conservative - metric to gauge the attainable Voc and to quantify the scope for improvement by reducing non radiative recombination. Provided that material quality issues are solved, we demonstrate - by transport and rigorous electromagnetic simulations - that light-trapping enhanced thin-film cells with twenty InAs/GaAs QD layers reach efficiency higher than 28% under unconcentrated light, ambient temperature. If photon recycling can be fully exploited, 30% efficiency is deemed to be feasible.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Photonics, Research group: ORC, Research group: Nanophotonics, Politecnico di Torino, Department of Applied Health Research, Radboud University Nijmegen, tf2 devices B.V.
Contributors: Cappelluti, F., Kim, D., van Eerden, M., Cédola, A. P., Aho, T., Bissels, G., Elsehrawy, F., Wu, J., Liu, H., Mulder, P., Bauhuis, G., Schermer, J., Niemi, T., Guina, M.
Pages: 83-92
Publication date: 2018
Peer-reviewed: Yes

Publication information

Journal: Solar Energy Materials and Solar Cells
Volume: 181
ISSN (Print): 0927-0248
Ratings: 
  • Scopus rating (2018): CiteScore 5.94 SJR 1.62 SNIP 1.681
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Renewable Energy, Sustainability and the Environment, Surfaces, Coatings and Films
Keywords: Epitaxial lift-off, Light-trapping, Quantum dot, Solar cell, Thin-film
Source: Scopus
Source ID: 85039853836

Research output: Contribution to journalArticleScientificpeer-review

Cascaded crystalline raman lasers for extended wavelength coverage: Continuous-wave, third-stokes operation

The development of high-power laser sources with narrow emission, tunable within the water transmission window around 1.7 μm, is of interest for applications as diverse as medical imaging and atmospheric sensing. Where suitable laser gain media are not available, operation in this spectral region is often achieved via nonlinear frequency conversion, and optical parametric oscillators (OPOs) are a common solution. A practical alternative to OPOs, to avoid birefringent-or quasi-phase-matching requirements, is the use of stimulated Raman scattering within a suitable material to convert a pump source to longer wavelengths via one or more Stokes shifts; however, as this is a χ3 nonlinear process, such frequency conversion is usually the preserve of high-energy pulsed lasers. Semiconductor disk lasers (SDLs), on the other hand, have very high-finesse external resonators, suitable for efficient intracavity nonlinear conversion even in continuous-wave (CW) operation. Here we report, to the best of our knowledge, the first continuous-wave third-Stokes crystalline Raman laser and the longest emission wavelength from an SDL-pumped Raman laser, achieving high power, CW output, and broad wavelength tuning around 1.73 μm. The KGd WO4 2 (KGW) Raman laser, which was intracavity-pumped by a 1.18 μm InGaAs-based SDL, demonstrated cascaded CW Stokes oscillation at 1.32 μm, 1.50 μm, and 1.73 μm with watt-level output achievable at each wavelength. The 1.73 μm Stokes emission was diffraction limited (M2 < 1.01) and narrow linewidth (<46 pm FWHM; measurement limited). By rotation of a birefringent filter placed within the fundamental resonator, we attained three tunable emission wavelength bands, one centred at each Stokes component, and achieved up to 65 nm tuning for the third-Stokes Raman laser from 1696 nm to 1761 nm. We have thus demonstrated a platform laser technology that takes well-developed InGaAs-based SDLs and provides spectral coverage and high performance in the near-infrared water transmission windows using commercially available components.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Photonics, University of Strathclyde
Contributors: Casula, R., Penttinen, J., Guina, M., Kemp, A. J., Hastie, J. E.
Number of pages: 8
Pages: 1406-1413
Publication date: 20 Nov 2018
Peer-reviewed: Yes

Publication information

Journal: Optica
Volume: 5
Issue number: 11
ISSN (Print): 2334-2536
Ratings: 
  • Scopus rating (2018): CiteScore 10.26 SJR 4.914 SNIP 3.162
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Atomic and Molecular Physics, and Optics
Source: Scopus
Source ID: 85059018872

Research output: Contribution to journalArticleScientificpeer-review

Continuous-wave, cascaded raman laser at 1.3, 1.5, and 1.7 μm

General information

Publication status: Published
MoE publication type: Not Eligible
Organisations: Photonics, Research group: ORC, Research group: Semiconductor Technology and Applications, University of Strathclyde
Contributors: Casula, R., Penttinen, J. P., Guina, M., Kemp, A. J., Hastie, J. E.
Publication date: 1 Jan 2017

Host publication information

Title of host publication: The European Conference on Lasers and Electro-Optics, CLEO_Europe 2017
Publisher: OSA - The Optical Society
ISBN (Electronic): 9781557528209

Publication series

Name: Optics InfoBase Conference Papers
Volume: Part F82-CLEO_Europe 2017
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Mechanics of Materials
Source: Scopus
Source ID: 85039902858

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Near-threshold high spin amplification in a 1300 nm GaInNAs spin laser

Using continuous-wave optical pumping of a spin-VCSEL at room temperature, we find high spin amplification of the pump close to threshold within the communications wavelength window, here at 1300 nm. This facilitates a strong switch from left to right circularly polarised light emission, which has potential applications in polarisation encoding for data communications. We use a simple spin flip model to fit the experimental results and discuss the VCSEL parameters that affect this amplification.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Photonics, Research group: ORC, Research group: Semiconductor Technology and Applications, University of Essex, University of Bristol
Contributors: Cemlyn, B., Adams, M., Harbord, E., Li, N., Henning, I. D., Oulton, R., Korpijärvi, V. M., Guina, M.
Publication date: 1 Aug 2018
Peer-reviewed: Yes

Publication information

Journal: Semiconductor Science and Technology
Volume: 33
Issue number: 9
Article number: 094005
ISSN (Print): 0268-1242
Ratings: 
  • Scopus rating (2018): CiteScore 2.4 SJR 0.744 SNIP 1.014
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Electrical and Electronic Engineering, Materials Chemistry
Keywords: spin amplification, spin laser, spin VCSEL
Source: Scopus
Source ID: 85053167963

Research output: Contribution to journalArticleScientificpeer-review

Self-alignment of RFID dies on four-pad patterns with water droplet for sparse self-assembly

This paper reports an in-depth study of a water-droplet-assisted self-alignment technique that self-aligns radio frequency identification (RFID) dies on four-pad patterns. The segmented structure of four hydrophilic pads on a hydrophobic substrate brings freedom to the design of the electrical functionality and the surface functionality. The paper investigates the influence of the key parameters that may affect the self-alignment in theory and experiment. The theoretical model justifies that RFID dies can be reliably aligned on the segmented four-pad pattern even when the initial placement error is as large as 50% of the size of the die and the gap between the four pads is about 10% of the size of the die. A method has been introduced to estimate the sufficient droplet volume for self-alignment. A series of experiments have been carried out to verify the results of the model. The experiments indicate that the self-alignment between the 730 × 730 νm RFID dies and the pattern occurs reliably when the releasing bias between the RFID die and antenna is less than 400 νm for patterns with 50 and 100 νm gaps, and successful self-alignment is possible even with greater bias of 500 νm.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Integrated Technologies for Tissue Engineering Research (ITTE), Aalto University, Department of Automation and Systems Technology
Contributors: Chang, B., Routa, I., Sariola, V., Zhou, Q.
Publication date: Sep 2011
Peer-reviewed: Yes

Publication information

Journal: Journal of Micromechanics and Microengineering
Volume: 21
Issue number: 9
Article number: 095024
ISSN (Print): 0960-1317
Ratings: 
  • Scopus rating (2011): CiteScore 2.43 SJR 1.036 SNIP 1.442
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Mechanics of Materials, Mechanical Engineering, Electrical and Electronic Engineering
Source: Scopus
Source ID: 80052254281

Research output: Contribution to journalArticleScientificpeer-review

Self-alignment in the stacking of microchips with mist-induced water droplets

This paper reports a novel and versatile water droplet self-alignment technique where the water is delivered in mist form onto the assembly site. The droplet forming process has been carefully investigated using machine vision, where each individual droplet on the microchip surface can be identified and the volume per surface area can be calibrated at a specific time. The result reveals that the volume of water droplets on the assembly surface grows linearly as a function of time. Self-alignment based on the mist-induced droplets has been studied, where a robotic microgripper is used to deliver the microchips on the assembly site. The paper also investigates the maximum tolerance of the initial placement error in stacking SU-8 chips 200 × 200 × 70 μm in size, and the possibility of stacking two SU-8 chips of different dimensions using the proposed self-alignment technique. Moreover, self-alignment of chips on hydrophilic/hydrophobic patterns covered by mist-induced water droplets has been studied. The experimental results indicate that this novel self-alignment technique is very promising. Furthermore, a statistical model has been used to validate the experimental results.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Integrated Technologies for Tissue Engineering Research (ITTE), Aalto University, Department of Automation and Systems Technology
Contributors: Chang, B., Sariola, V., Jääskeläinen, M., Zhou, Q.
Publication date: Jan 2011
Peer-reviewed: Yes

Publication information

Journal: Journal of Micromechanics and Microengineering
Volume: 21
Issue number: 1
Article number: 015016
ISSN (Print): 0960-1317
Ratings: 
  • Scopus rating (2011): CiteScore 2.43 SJR 1.036 SNIP 1.442
Original language: English
ASJC Scopus subject areas: Mechanical Engineering, Electrical and Electronic Engineering, Mechanics of Materials, Electronic, Optical and Magnetic Materials
Source: Scopus
Source ID: 78651517828

Research output: Contribution to journalArticleScientificpeer-review

Two-part stretchable passive UHF RFID textile tags

We present two-part stretchable passive UHF RFID textile tags using electro-textile and embroidered antennas, and test their reliability under cyclic stretching. The tags'wireless performance is evaluated initially and after up to a 100 stretching cycles. The measurement results show that the initial read ranges of the electro-textile and embroidered tags are 5.5 meters and 6.3 meters, respectively. The cyclic strain does not affect the read ranges of the embroidered tags, and the read ranges of the electro-textile tags are only slightly affected, i.e., decreased about 50 cm after the first stretching cycle, and then settled Based on these results, the use of two-part structures can improve the strain reliability of textile RFID tags.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Faculty of Biomedical Sciences and Engineering, Mathematics, Research group: Wireless Identification and Sensing Systems Research Group, Southeast University
Contributors: Chen, X., He, H., Chen, L., Raumonen, P., Ukkonen, L., Virkki, J.
Number of pages: 4
Pages: 3318-3321
Publication date: 22 May 2017

Host publication information

Title of host publication: 2017 Progress in Electromagnetics Research Symposium - Spring, PIERS 2017
Publisher: Electromagnetics Academy
ISBN (Electronic): 9781509062690
ASJC Scopus subject areas: Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials
Source: Scopus
Source ID: 85044939028

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Fabrication and reliability evaluation of passive UHF RFID T-shirts

In this paper, we present textile antennas fabricated for T-shirt RFID applications by cutting from commercially available electro-textile, by sewing with conductive thread, and by 3D printing with stretchable silver ink on a 100 % cotton fabric. The ready tags with attached ICs are coated with a protective stretchable encapsulant. The wireless performance of the T-shirt tags is evaluated initially as well as after seven washing cycles, followed by nine washing-drying cycles in a household washing and drying machines. The initial read ranges of all kinds of tags, when measured on-body, are around 3.5 meters. Based on the reliability testing results, the coating effectively protects the components from cyclic washing and drying.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Faculty of Biomedical Sciences and Engineering, Research group: Wireless Identification and Sensing Systems Research Group, Department of Electronic Engineering, City University of Hong Kong
Contributors: Chen, X., He, H., Ukkonen, L., Virkki, J., Lu, Y., Lam, H.
Number of pages: 4
Pages: 1-4
Publication date: 8 Jun 2018

Host publication information

Title of host publication: 2018 IEEE International Workshop on Antenna Technology, iWAT2018 - Proceedings
Publisher: IEEE
ISBN (Electronic): 9781538618516
ASJC Scopus subject areas: Instrumentation, Computer Networks and Communications, Electronic, Optical and Magnetic Materials
Keywords: 3D Printing, electro-textiles, embroidery, passive UHF RFID, T-shirts, textiles, washing, wearable electronics

Bibliographical note

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Source: Scopus
Source ID: 85050037887

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Design, Fabrication, and Wireless Evaluation of a Passive 3D-printed Moisture Sensor on a Textile Substrate

This paper introduces the first steps of fabrication and the initial wireless performance evaluation of a passive ultra-high frequency (UHF) radiofrequency identification (RFID)-based moisture sensor on a textile substrate. The sensor antenna was embroidered on a stretchable fabric firstly, and then embedded inside a 3D-printed platform. This 3D-printed sensor material changes its properties permanently, after exposure to a high moisture environment. Thus, the sensor can detect the increased moisture in the environment. Based on our initial results, this information can be clearly read from the changed backscattered signal of the embedded passive RFID tag. The fabricated sensor has an initial peak read range of 6 meters. After being dipped into water for 2 hours, the read range of the sensor has a significant decrease, but it is still readable from 5 meters. Thus, this moisture sensor can be read wirelessly from a convenient distance, when considering practical use of moisture sensors.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: BioMediTech
Contributors: Chen, X., He, H., Khan, Z., Sydänheimo, L., Ukkonen, L., Virkki, J.
Number of pages: 4
Pages: 1027-1030
Publication date: 1 Jun 2019

Host publication information

Title of host publication: 2019 PhotonIcs and Electromagnetics Research Symposium - Spring, PIERS-Spring 2019 - Proceedings
Publisher: IEEE
Article number: 9017301
ISBN (Electronic): 9781728134031

Publication series

Name: Progress in Electromagnetics Research Symposium
Volume: 2019-June
ISSN (Print): 1559-9450
ISSN (Electronic): 1931-7360
ASJC Scopus subject areas: Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials
Source: Scopus
Source ID: 85082012079

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Maintenance-free moisture sensor on dishcloth substrate

In this study, a passive UHF RFID-based moisture sensor is fabricated and evaluated. The sensor tag can sense the high humidity of the environment and indicate it with a permanent change in its backscattered signal. The sensor tag antenna and antenna-IC interconnections are fabricated on a biodegradable dishcloth material using conductive thread. The sensors are tested in an anechoic chamber and in normal office conditions, when initially dry, after dipped into water for 1 minute, and again after 24 hours of drying in air. These sensor tags initially show read ranges of 6-9 meters throughout the global UHF RFID frequency band. When wet, the read range decreases to 5 meters, while after 24 hours of drying, the read ranges of the tags permanently decrease to around 2-4 meters. The dishcloth material comes thicker when wet, also causing a change to the embroidered antenna structure, finally causing the permanent change in the backscattered signal. In normal office conditions, moisture causes the average backscattered signal an obvious change from around -66 dBm to -69 dBm.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: BioMediTech, City University of Hong Kong
Contributors: Chen, X., He, H., Yang, Y., Gou, M., Sydanheimo, L., Ukkonen, L., Virkki, J.
Number of pages: 4
Pages: 2418-2421
Publication date: 1 Dec 2019

Host publication information

Title of host publication: 2019 Photonics and Electromagnetics Research Symposium - Fall, PIERS - Fall 2019 - Proceedings
Publisher: IEEE
Article number: 9021487
ISBN (Electronic): 9781728153049
ASJC Scopus subject areas: Electrical and Electronic Engineering, Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials, Mathematical Physics

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Compressive strain measurement using RFID patch antenna sensors

In this research, two radiofrequency identification (RFID) antenna sensor designs are tested for compressive strain measurement. The first design is a passive (battery-free) folded patch antenna sensor with a planar dimension of 61mm × 69mm. The second design is a slotted patch antenna sensor, whose dimension is reduced to 48mm × 44mm by introducing slots on antenna conducting layer to detour surface current path. A three-point bending setup is fabricated to apply compression on a tapered aluminum specimen mounted with an antenna sensor. Mechanics-electromagnetics coupled simulation shows that the antenna resonance frequency shifts when each antenna sensor is under compressive strain. Extensive compression tests are conducted to verify the strain sensing performance of the two sensors. Experimental results confirm that the resonance frequency of each antenna sensor increases in an approximately linear relationship with respect to compressive strain. The compressive strain sensing performance of the two RFID antenna sensors, including strain sensitivity and determination coefficient, is evaluated based on the experimental data.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Sensing Systems for Wireless Medicine (MediSense), Georgia Institute of Technology, Georgia Institute of Technology, School of Electrical and Computer Engineering, Virginia Tech
Contributors: Cho, C., Yi, X., Wang, Y., Tentzeris, M. M., Leon, R. T.
Publication date: 2014

Host publication information

Title of host publication: Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2014
Volume: 9061
Publisher: SPIE
Article number: 90610X
ISBN (Print): 9780819499875
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Computer Science Applications, Applied Mathematics, Electrical and Electronic Engineering
Keywords: Folded patch antenna, Passive wireless sensor, RFID, Slotted patch antenna, Strain sensor
Source: Scopus
Source ID: 84902151393

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

A near-infrared optoelectronic approach to detection of road conditions

We introduce and test an original approach for the optical assessment of road conditions due to various atmospheric perturbations such as the presence of ice, wet surfaces and rain. The technique is based on measuring diffused and reflected light under near infrared illumination, extracting the polarization contrast after reflection. Several tests, carried out on various types of asphalt and various thicknesses of water and ice layers, demonstrate that the system exhibits selectivity and robustness to allow the recognition of dry asphalt, water-layered, wet asphalt and asphalt with ice.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Frontier Photonics, University “Roma Tre”, Nonlinear Optics and OptoElectronics Lab
Contributors: Colace, L., Santoni, F., Assanto, G.
Number of pages: 4
Pages: 633-636
Publication date: May 2013
Peer-reviewed: Yes

Publication information

Journal: Optics and Lasers in Engineering
Volume: 51
Issue number: 5
ISSN (Print): 0143-8166
Ratings: 
  • Scopus rating (2013): CiteScore 2.4 SJR 0.864 SNIP 1.851
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Electrical and Electronic Engineering, Atomic and Molecular Physics, and Optics, Mechanical Engineering
Keywords: Ice detection, Near-infrared, Optical sensors
Source: Scopus
Source ID: 84874118385

Research output: Contribution to journalArticleScientificpeer-review

Noise characterization of Ge/Si photodetectors

We invesyigate the noise in Ge/Si photodiodes. The noise performance is characterized by current voltage characteristics and spectral analysis and the results compared with reference Ge/Ge photodetectors. Both thermal and shot noise are of the same order, while Ge/Si devices exhibit a significantly larger 1/f noise.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Frontier Photonics, University “Roma Tre”, Nonlinear Optics and OptoElectronics Lab
Contributors: Colace, L., Scacchi, A., Assanto, G.
Number of pages: 3
Pages: 290-292
Publication date: 2011

Host publication information

Title of host publication: 8th IEEE International Conference on Group IV Photonics, GFP 2011
Article number: 6053793
ISBN (Print): 9781424483389
ASJC Scopus subject areas: Electrical and Electronic Engineering, Ceramics and Composites, Electronic, Optical and Magnetic Materials
Keywords: Ge/Si photodetectors, near infrared, noise
Source: Scopus
Source ID: 81355136186

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Germanium-on-glass solar cells

We report on the fabrication and characterization of Ge solar cells on glass realized by layer transfer and epitaxial regrowth. These devices exhibit typical conversion efficiency exceeding 2.4% under AM1.5 irradiation and maximum efficiency of 3.7% under concentrated excitation. This approach enables flexible and affordable multi-junction engineering for solar energy conversion.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Frontier Photonics, University “Roma Tre”, Nonlinear Optics and OptoElectronics Lab, Barclays
Contributors: Colace, L., Sorianello, V., Maragliano, C., Assanto, G., Fulgoni, D., Nash, L., Palmer, M.
Number of pages: 3
Pages: 255-257
Publication date: 2011

Host publication information

Title of host publication: 8th IEEE International Conference on Group IV Photonics, GFP 2011
Article number: 6053781
ISBN (Print): 9781424483389
ASJC Scopus subject areas: Electrical and Electronic Engineering, Ceramics and Composites, Electronic, Optical and Magnetic Materials
Keywords: germanium, solar cells, wafer bonding
Source: Scopus
Source ID: 81355136195

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Optical power monitors in Ge monolithically integrated on SOI chips

We report on the fabrication and operation of optical power monitors monolithically integrated on silicon-on-insulator optical chips. The devices consist of near-infrared waveguide pn heterojunction photodiodes in evaporated germanium. The low temperature growth of Ge is compatible with silicon waveguide technology. The photodetectors exhibit typical responsivities of 10-30 mA/W; the power monitors are used with front-end trans-impedance amplifiers based on commercially available operational amplifiers and can operate with optical signals as small as 10 nW, with errors below 0.2% and 2% at 1 and 0.1 μW, respectively.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Frontier Photonics, University “Roma Tre”, Nonlinear Optics and OptoElectronics Lab
Contributors: Colace, L., Sorianello, V., Romagnoli, M., Socci, L., Assanto, G.
Number of pages: 4
Pages: 514-517
Publication date: Apr 2011
Peer-reviewed: Yes

Publication information

Journal: Microelectronic Engineering
Volume: 88
Issue number: 4
ISSN (Print): 0167-9317
Ratings: 
  • Scopus rating (2011): CiteScore 1.8 SJR 0.813 SNIP 1.148
Original language: English
ASJC Scopus subject areas: Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Surfaces, Coatings and Films, Atomic and Molecular Physics, and Optics, Condensed Matter Physics
Keywords: Germanium, Integrated optoelectronics, Photodetectors, Powermonitor, Silicon-on-insulator
Source: Scopus
Source ID: 79751538504

Research output: Contribution to journalArticleScientificpeer-review

Inkjet catalyst printing and electroless copper deposition for low-cost patterned microwave passive devices on paper

A scalable, low-cost process for fabricating copper-based microwave components on flexible, paper-based substrates is demonstrated. An inkjet printer is used to deposit a catalyst-bearing solution (tailored for such printing) in a desired pattern on commercially-available, recyclable, non-toxic (Teslin®) paper. The catalystbearing paper is then immersed in an aqueous copper-bearing solution to allow for electroless deposition of a compact and conformal layer of copper in the inkjet-derived pattern. Meander monopole antennas comprised of such electroless-deposited copper patterns on paper exhibited comparable performance as for antennas synthesized via inkjet printing of a commercially-available silver nanoparticle ink. However, the solution-based patterning and electroless copper deposition process avoids nozzle-clogging problems and costs associated with noble metal particle-based inks. This process yields compact conductive copper layers without appreciable oxidation and without the need for an elevated temperature, post-deposition thermal treatment commonly required for noble metal particle-based ink processes. This low-cost copper patterning process is readily scalable on virtually any substrate and may be used to generate a variety of copper-based microwave devices on flexible, paper-based substrates.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Sensing Systems for Wireless Medicine (MediSense), Georgia Institute of Technology, School of Electrical and Computer Engineering, Georgia Institute of Technology
Contributors: Cook, B. S., Fang, Y., Kim, S., Le, T., Goodwin, W. B., Sandhage, K. H., Tentzeris, M. M.
Number of pages: 8
Pages: 669-676
Publication date: Sep 2013
Peer-reviewed: Yes

Publication information

Journal: Electronic Materials Letters
Volume: 9
Issue number: 5
ISSN (Print): 1738-8090
Ratings: 
  • Scopus rating (2013): CiteScore 3.39 SJR 1.219 SNIP 2.498
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials
Keywords: antennas, copper metallization, flexible and recyclable substrates, inkjet printed electronics, paper-bearing electronics, RF devices
Source: Scopus
Source ID: 84883808468

Research output: Contribution to journalArticleScientificpeer-review

Novel oxyfluorophosphate glasses and glass-ceramics

Effect of CaF2 addition at the expense of CaO on the thermal, physical, optical and structural properties of glasses in the NaPO3-CaO system was studied. The glasses were prepared by the conventional melt quenching method. For each glass, the thermal properties were studied by differential thermal analysis (DTA) and the optical properties by UV-Vis-NIR spectroscopy. The changes in the glass structure induced by the progressive replacement of CaO by CaF2 were investigated using IR and Raman spectroscopies. The glasses were heat treated at 20 °C above their respective glass transition temperature for 17 h to form nuclei and then at their peak crystallization temperature for 1 h to grow the nuclei into crystals. An increase in the CaF2 content increased the polymerization of the phosphate network leading to shift of the band gap to lower wavelength and reduced the crystallization tendency of the glasses. At least two crystalline phases precipitated in all the investigated glasses, the composition of which depended on the CaF2 content. Finally, bulk crystallization was suspected to occur in the oxyfluorophosphate glasses.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Electronics and Communications Engineering, Research group: Biomaterials and Tissue Engineering Group, Abo Akademi University, University of Turku
Contributors: Cui, S., Massera, J., Lastusaari, M., Hupa, L., Petit, L.
Number of pages: 5
Pages: 40-44
Publication date: 1 Aug 2016
Peer-reviewed: Yes

Publication information

Journal: Journal of Non-Crystalline Solids
Volume: 445-446
ISSN (Print): 0022-3093
Ratings: 
  • Scopus rating (2016): CiteScore 2.02 SJR 0.685 SNIP 1.154
Original language: English
ASJC Scopus subject areas: Condensed Matter Physics, Ceramics and Composites, Electronic, Optical and Magnetic Materials, Materials Chemistry
Keywords: Crystallization, Fluorophosphate glasses and glass-ceramics, Raman and IR spectroscopies, XRD
Source: Scopus
Source ID: 84969872500

Research output: Contribution to journalArticleScientificpeer-review

Development of a new illumination procedure for photodynamic therapy of the abdominal cavity

A homogeneous illumination of intra-abdominal organs is essential for successful photodynamic therapy of the abdominal cavity. Considering the current lack of outstanding light-delivery systems, a new illumination procedure was assessed. A rat model of peritoneal carcinomatosis was used. Four hours after intraperitoneal injection of hexaminolevulinate, a square illuminating panel connected to a 635-nm laser source was inserted vertically into the abdominal cavity. The abdominal incision was sutured and a pneumoperitoneum created prior to illumination. Light dosimetry was based on the calculation of the peritoneal surface by MRI. The rats were treated with a light dose of 20,10, 5 or 2.5 J/cm2 administered continuously with an irradiance of 7 mW/cm 2. The homogeneity of the cavity illumination was assessed by quantification of the photobleaching of the tumor lesions according to their localization and by scoring of that of the liver and of the bowel immediately after treatment. Photobleaching quantification for tumor lesions relied on the calculation of the fluorescence intensity ratio (after/before treatment) after recording of the lesions during blue-light laparoscopy and determination of their fluorescence intensity with Sigmascan Pro software. The procedure led to a homogeneous treatment of the abdominal cavity. No statistical difference was observed for the photobleaching values according to the localization of the lesions on the peritoneum (p = 0.59) and photobleaching of the liver and of the intestine was homogeneous. We conclude that this procedure can successfully treat the major sites involved in peritoneal carcinomatosis.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Frontier Photonics, Lille University Hospital - CHRU, Univ Lille Nord de France, GDR 3049
Contributors: Cuyon, L., Lesage, J. C., Betrouni, N., Mordon, S.
Publication date: Mar 2012
Peer-reviewed: Yes

Publication information

Journal: JOURNAL OF BIOMEDICAL OPTICS
Volume: 17
Issue number: 3
Article number: 038001
ISSN (Print): 1083-3668
Ratings: 
  • Scopus rating (2012): CiteScore 2.55 SJR 1.292 SNIP 1.329
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Atomic and Molecular Physics, and Optics, Biomaterials, Biomedical Engineering
Keywords: Hexaminolevulinate, Light dosimetry, Peritoneal carcinomatosis, Photobleaching, Photodynamic therapy
Source: Scopus
Source ID: 84864951116

Research output: Contribution to journalArticleScientificpeer-review

Novel highly-efficient and misalignment insensitive wireless power transfer systems utilizing Strongly Coupled Magnetic Resonance principles

The wireless powering efficiency of traditional Strongly Coupled Magnetic Resonance (SCMR) systems is highly sensitive to the alignment between the transmitter and receiver elements; an issue that has limited their applicability in practical wireless power transfer systems. This paper proposes a novel set of SCMR-based topologies that are insensitive to misalignment and isotropic while providing large wireless powering efficiencies. The systems, which are presented here, achieve power transfer efficiencies above 50% over the complete misalignment range of 0-90° with performance that is significantly better than typical SCMR elements.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Sensing Systems for Wireless Medicine (MediSense), Florida International University, Georgia Institute of Technology
Contributors: Daerhan, D., Jonah, O., Hu, H., Georgakopoulos, S. V., Tentzeris, M. M.
Number of pages: 4
Pages: 759-762
Publication date: 11 Sep 2014

Host publication information

Title of host publication: Proceedings - Electronic Components and Technology Conference
Publisher: Institute of Electrical and Electronics Engineers Inc.
Article number: 6897370
ISBN (Electronic): 9781479924073
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Electrical and Electronic Engineering
Source: Scopus
Source ID: 84907906443

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Performance enhancement of the RFID EPC Gen2 protocol by exploiting collision re-covery

Maximizing the Radio Frequency Identification (RFID) performance is one of the main challenges in application domains, such as logistics and supply chain management, where the undesired effect of Tag collisions can significantly degrade the speed of the inventory process. The dominating UHF EPC Class-1 Generation- 2 (EPC Gen2) protocol only specifies collision avoidance algorithms but makes no provision for collision resolution. In this paper, performance enhancement of the EPC Gen2 standard exploiting Tag collision recovery is demonstrated, for the first time, in real time with measurements. Three simple and effective approaches to handle successful Tag acknowledgments of recovered collided packets are proposed and implemented on a software-defined Reader and programmable Tags. The attained benefits over the conventional EPC Gen2 MAC scheme are significant: the throughput per time slot is increased by 72% while the overall time required to inventory the Tag population is reduced by 26%. The effectiveness of the proposed approach and the validity of the achieved results are confirmed by the good agreement with simulations reported in the literature.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Sensing Systems for Wireless Medicine (MediSense), Università del Salento, Georgia Institute of Technology, School of Electrical and Computer Engineering
Contributors: De Donno, D., Tarricone, L., Catarinucci, L., Lakafosis, V., Tentzeris, M. M.
Number of pages: 20
Pages: 53-72
Publication date: 2012
Peer-reviewed: Yes

Publication information

Journal: Progress in Electromagnetics Research B
Issue number: 43
ISSN (Print): 1937-6472
Ratings: 
  • Scopus rating (2012): CiteScore 1.69 SJR 0.51 SNIP 1.216
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Electrical and Electronic Engineering
Source: Scopus
Source ID: 84866454701

Research output: Contribution to journalArticleScientificpeer-review

RFDNA: A wireless authentication system on flexible substrates

The design and development of RFDNA, an RF authentication system consisting of wirelessly transmitting and receiving electromagnetic signals in the presence of a constellation of dense metals called certificates of authenticity that act as reflecting obstacles, has been performed [1]. The unique feature of this system is that the authentication is physical (hardware-based). Therefore, an integration process necessitates the manufacturing of certificates of authenticity to be durable and able to withstand normal wear and tear. In this system, one of the drawbacks has been the materials that have been used in the design. The materials for the readers have been designed on bulkier, non-conformable substrates, such as FR4. Additionally, the certificates of authenticity consisted of metal wires that have been densely placed into heated plastic that is hardened to maintain the wires' position. In order to realize a more practical implementation, a new class of certificates of authenticity and readers need to be manufactured on flexible substrates. This paper will focus on the design of a new antenna for an RFDNA reader on flexible substrates.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Sensing Systems for Wireless Medicine (MediSense), Microsoft Research, Georgia Institute of Technology, School of Electrical and Computer Engineering
Contributors: Dejean, G., Lakafosis, V., Traille, A., Lee, H., Gebara, E., Tentzeris, M., Kirovski, D.
Number of pages: 6
Pages: 1332-1337
Publication date: 2011

Host publication information

Title of host publication: 2011 IEEE 61st Electronic Components and Technology Conference, ECTC 2011
Article number: 5898684
ISBN (Print): 9781612844978
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Electrical and Electronic Engineering
Source: Scopus
Source ID: 79960402541

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Processing and Characterization of Bioactive Borosilicate Glasses and Scaffolds with Persistent Luminescence

In this proceeding, we report our latest results on the development of borosilicate glasses with persistent luminescence (PeL). Those PeL glasses were processed by adding PeL microparticles (MPs) in the glass using the direct doping method. First, we explain the challenges to balance the survival and dispersion of MPs when preparing borosilicate glasses using this method. Then, we show that scaffold can be obtained using the sintering process from these glasses but also by adding PeL microparticles (MPs) in the glass powder prior to sintering. Finally, we discuss the impact of the scaffold fabrication process on the PeL properties of the MPs.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Faculty of Biomedical Sciences and Engineering, Research group: Biomaterials and Tissue Engineering Group, Photonics, Research group: Photonics Glasses, Turku University of Applied Science
Contributors: Del Cerro, P. R., Saarinen, M., Massera, J., Norrbo, I., Lastusaari, M., Petit, L.
Number of pages: 5
Publication date: 26 Sep 2018

Host publication information

Title of host publication: 2018 20th International Conference on Transparent Optical Networks, ICTON 2018
Volume: 2018-July
Publisher: IEEE COMPUTER SOCIETY PRESS
Article number: 8473916
ISBN (Electronic): 9781538666043

Publication series

Name: Conference proceedings : International Conference on Transparent Optical Networks
ISSN (Print): 2161-2056
ASJC Scopus subject areas: Computer Networks and Communications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials
Keywords: borosilicate glasses, direct particles doping method, Dy microparticles, persistent luminescence, sintering, SrAlO:Eu

Bibliographical note

INT=fot,"Del Cerro, P. Roldan"

Source: Scopus
Source ID: 85055532457

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Novel borosilicate bioactive scaffolds with persistent luminescence

Persistent luminescent amorphous borosilicate scaffolds were successfully prepared, for the first time, with a porosity of >70% using the burn-off technique. The persistent luminescence was obtained by adding the SrAl2O4:Eu2+,Dy3+ microparticles: i) in the glass melt or ii) in the glass crushed into powder prior to the sintering. The scaffolds prepared by adding the microparticles in the glass melt exhibits lower persistent luminescence and a slower reaction rate in simulated body fluid than the scaffolds prepared by adding the microparticles in the glass powder due to the release of strontium from the microparticles into the glass during the glass melting.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: BioMediTech, Physics, Tampere University, Turun yliopisto
Contributors: Del Cerro, P. R., Teittinen, H., Norrbo, I., Lastusaari, M., Massera, J., Petit, L.
Number of pages: 9
Pages: 1-9
Publication date: 2020
Peer-reviewed: Yes

Publication information

Journal: Biomedical Glasses
Volume: 6
Issue number: 1
ISSN (Print): 2299-3932
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Ceramics and Composites, Surfaces, Coatings and Films, Materials Chemistry
Keywords: Borosilicate glasses, Direct particle doping method, Dy microparticles, In-vitro testing, Persistent luminescence, Scaffold, SrAlO:Eu
Source: Scopus
Source ID: 85085038962

Research output: Contribution to journalArticleScientificpeer-review

Test Results of the LARP Nb3Sn Quadrupole HQ03a

The U.S. LHC Accelerator Research Program (LARP) has been developing Nb3Sn quadrupoles of increasing performance for the high-luminosity upgrade of the large hadron collider. The 120-mm aperture high-field quadrupole (HQ) models are the last step in the RD phase supporting the development of the new IR Quadrupoles (MQXF). Three series of HQ coils were fabricated and assembled in a shell-based support structure, progressively optimizing the design and fabrication process. The final set of coils consistently applied the optimized design solutions and was assembled in the HQ03a model. This paper reports a summary of the HQ03a test results, including training, mechanical performance, field quality, and quench studies.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Fermi National Accelerator Laboratory, Brookhaven National Laboratory, European Organization for Nuclear Research, Lawrence Berkeley National Laboratory
Contributors: DiMarco, J., Ambrosio, G., Anerella, M., Bajas, H., Chlachidze, G., Borgnolutti, F., Bossert, R., Cheng, D., Dietderich, D., Felice, H., Holik, T., Pan, H., Ferracin, P., Ghosh, A., Godeke, A., Hafalia, A. R., Marchevsky, M., Orris, D., Ravaioli, E., Sabbi, G., Salmi, T., Schmalzle, J., Stoynev, S., Strauss, T., Sylvester, C., Tartaglia, M., Todesco, E., Wanderer, P., Wang, X., Yu, M.
Publication date: 1 Jun 2016
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Applied Superconductivity
Volume: 26
Issue number: 4
Article number: 4005105
ISSN (Print): 1051-8223
Ratings: 
  • Scopus rating (2016): CiteScore 1.42 SJR 0.398 SNIP 1.132
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Electrical and Electronic Engineering
Keywords: High field accelerator magnets, NbSn
Source: Scopus
Source ID: 84971631243

Research output: Contribution to journalArticleScientificpeer-review

First principles prediction of the solar cell efficiency of chalcopyrite materials  AgMX2(M=In, Al; X=S, Se, Te)

Using the spectroscopic limited maximum efficiency, and Shockley and Queisser predictor models, we compute the solar efficiency of the chalcopyrites AgMX 2 (M = In, Al; X = S, Se, Te). The results presented are based on the estimation of the electronic and optical properties obtained from first principles density functional theory as well as the many-body perturbation theory calculations. The results from this report were consistent with the experimental data.The optical bandgap was accurately estimated from the absorption spectra, obtained by solving the Bethe and Salpeter equation. Fitting the Tauc's plot on the absorption spectra, we also predicted that the materials studied have a direct allowed optical transition. The theoretical estimations of the solar cell performance showed that the efficiencies from the Shockley and Queisser model are higher than those from the spectroscopic limited maximum efficiency model. This improvement is attributed to the absorption, the recombination processes and the optical transition accounted in the calculation of the efficiency.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Electrical Engineering, University of South Africa, University of Witwatersrand
Contributors: Dongho-Nguimdo, G. M., Igumbor, E., Zambou, S., Joubert, D. P.
Publication date: 1 Dec 2019
Peer-reviewed: Yes

Publication information

Journal: Computational Condensed Matter
Volume: 21
Article number: e00391
ISSN (Print): 2352-2143
Ratings: 
  • Scopus rating (2019): SJR 0.341 SNIP 0.706
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Materials Science (miscellaneous), Condensed Matter Physics, Materials Chemistry
Keywords: Chalcopyrites, First principles, Solar cell efficiency
Source: Scopus
Source ID: 85065198754

Research output: Contribution to journalArticleScientificpeer-review

Electronic transport in n-type modulation-doped AlGaAs/GaAsBi quantum well structures: Influence of Bi and thermal annealing on electron effective mass and electron mobility

We investigate electronic transport properties of as-grown and annealed n-type modulation-doped Al0.15Ga0.85As/GaAs1-xBix (x = 0 and 0.04) quantum well (QW) structures using magnetotransport measurements in the temperature range 4.2 K and 60 K and at magnetic fields up to 18 T. Thermal annealing process was applied at two different temperatures, 700 °C and 350 °C during 60 s and 180 s, respectively. We find that electron effective mass and 2D electron density in as-grown Bi-containing sample are slightly lower than that in Bi-free one. Furthermore, quantum electron mobility and quantum scattering time are observed to be decreased in Bi-containing samples. The annealing process at 700 °C causes a slight increase in electron effective mass and 2D electron density. A negligible decrease in electron effective mass and an increase in 2D electron density are determined following annealing at 350 °C. The observed change in electron effective mass following thermal annealing process is attributed to changing 2D electron density in the samples. No improvement on quantum electron mobility and quantum scattering time are observed following thermal annealing at both process temperatures. We determine that one electron subband (e1) for as-grown and annealed (at 700 °C for 60 s) Bi-containing QWs and two electron subbands (e1 and e2) for the annealed (at 350 °C for 180 s) GaAsBi QW sample and the Bi-free QW sample contribute to electronic transport. Our results reveal that there is no significant direct effect of Bi on effective electron mass, but an indirect effect, in which Bi can provoke changes in 2D electron density and hence causes not to observe actual band-edge electron mass but a deviation from its band-edge value. Therefore, it can be concluded that dispersion curve of conduction band does not change as an effect of Bi incorporation in GaAs.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Physics, Istanbul University, Eskişehir Technical University (ESTU), Istanbul University-Cerrahpasa
Contributors: Donmez, O., Aydin, M., Ardali, Yildirim, S., Tiraş, E., Nutku, F., Cetinkaya, C., okduygulular, E., Puustinen, J., Hilska, J., Guina, M., Erol, A.
Publication date: 2020
Peer-reviewed: Yes

Publication information

Journal: Semiconductor Science and Technology
Volume: 35
Issue number: 2
Article number: 025009
ISSN (Print): 0268-1242
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Electrical and Electronic Engineering, Materials Chemistry
Keywords: bismuthindependent effective mass, Electron effective mass in GaAsBi, electron mobility in GaAsBi, electronic transport in GaAsBi, n-type GaAsBi
Source: Scopus
Source ID: 85082305824

Research output: Contribution to journalArticleScientificpeer-review

Real-time measurements of ultrafast instabilities in nonlinear fiber optics: Recent advances

Recent years have seen renewed interest in the study of nonlinear fibre laser and propagation dynamics through the use of real-time measurement techniques for non-repetitive ultrafast optical signals. In this paper we review our recent work in this field using dispersive Fourier Transform and Time Lens techniques.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Physics, UMR 6174
Contributors: Dudley, J. M., Ryczkowski, P., Närhi, M., Billet, C., Merolla, J. M., Lapre, C., Meng, F., Lacourt, P. A., Genty, G.
Publication date: 1 Jul 2019

Host publication information

Title of host publication: 21st International Conference on Transparent Optical Networks, ICTON 2019
Publisher: IEEE
ISBN (Electronic): 9781728127798

Publication series

Name: International Conference on Transparent Optical Networks
ISSN (Electronic): 2161-2064
ASJC Scopus subject areas: Computer Networks and Communications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials

Bibliographical note

jufoid=72297

Source: Scopus
Source ID: 85073069033

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Simulation of photon-photon resonance enhanced direct modulation bandwidth of DFB lasers

Simulations and experimental results of high-frequency photon-photon resonance are used to examine the possibilities to extend the direct modulation bandwidth in dual-mode distributed feedback lasers beyond the conventional limit set by the carrier-photon resonance.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Optoelectronics Research Centre, Research group: Semiconductor Technology and Applications, Brighterwave Inc, Politecnico di Torino
Contributors: Dumitrescu, M., Uusitalo, T., Virtanen, H., Laakso, A., Bardella, P., Montrosset, I.
Number of pages: 2
Pages: 147-148
Publication date: 17 Aug 2016

Host publication information

Title of host publication: 16th International Conference on Numerical Simulation of Optoelectronic Devices, NUSOD 2016
Publisher: IEEE
ISBN (Electronic): 978-1-4673-8603-6
ASJC Scopus subject areas: Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Modelling and Simulation, Numerical Analysis

Bibliographical note

EXT="Laakso, A."

Source: Scopus
Source ID: 84987641496

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Efficient photon upconversion at remarkably low annihilator concentrations in a liquid polymer matrix: when less is more

A green-to-blue triplet-triplet annihilation upconversion of 24.5% quantum yield was achieved at a remarkably low 600 μM annihilator concentration in a viscous polymer matrix. This was made possible by utilizing a ZnTPP-based photosensitizer with exceptionally long 11 ms phosphorescence lifetime. Higher 3 mM annihilator concentration resulted in lower 24% upconversion quantum yield.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Chemistry and Bioengineering
Contributors: Durandin, N. A., Isokuortti, J., Efimov, A., Vuorimaa-Laukkanen, E., Tkachenko, N. V., Laaksonen, T.
Number of pages: 4
Pages: 14029-14032
Publication date: 2018
Peer-reviewed: Yes

Publication information

Journal: Chemical Communications
Volume: 54
Issue number: 99
ISSN (Print): 1359-7345
Ratings: 
  • Scopus rating (2018): CiteScore 6.12 SJR 2.177 SNIP 1.145
Original language: English
ASJC Scopus subject areas: Catalysis, Electronic, Optical and Magnetic Materials, Ceramics and Composites, Chemistry(all), Surfaces, Coatings and Films, Metals and Alloys, Materials Chemistry
Keywords: triplet-triplet annihilation, triplet-triplet energy transfer, triplet state lifetime, upconversion, triplet fusion
URLs: 
Source: Scopus
Source ID: 85058301188

Research output: Contribution to journalArticleScientificpeer-review

Two-time coherence of pulse trains and the integrated degree of temporal coherence

We examine the temporal coherence properties of trains of nonidentical short optical pulses in the framework of the second-order coherence theory of nonstationary light. Considering Michelson's interferometric measurement of temporal coherence, we demonstrate that time-resolved interferograms reveal the full two-time temporal coherence function of the partially coherent pulse train. We also show that the result given by the time-integrated Michelson interferogram equals the true degree of temporal coherence only when the pulse train is quasistationary, i.e., the coherence time is a small fraction of the pulse duration. True two-time and integrated coherence functions produced by specific models representing perturbed trains of mode-locked pulses and supercontinuum pulse trains produced in nonlinear fibers are illustrated.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Physics, Research group: Nonlinear Fiber Optics, Research area: Optics, Frontier Photonics, Ita-Suomen yliopisto, Institute of Photonics
Contributors: Dutta, R., Friberg, A. T., Genty, G., Turunen, J.
Number of pages: 7
Pages: 1631-1637
Publication date: 2015
Peer-reviewed: Yes

Publication information

Journal: Journal of the Optical Society of America A: Optics Image Science and Vision
Volume: 32
Issue number: 9
ISSN (Print): 1084-7529
Ratings: 
  • Scopus rating (2015): CiteScore 1.61 SJR 0.918 SNIP 1.103
Original language: English
ASJC Scopus subject areas: Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials, Computer Vision and Pattern Recognition
Source: Scopus
Source ID: 84943414423

Research output: Contribution to journalArticleScientificpeer-review

Deformation of lamellar γ-TiAl below the general yield stress

The occurrence of plasticity below the macroscopic yield stress during tensile monotonic loading of nearly lamellar Ti-45Al-2Nb-2Mn(at%)-0.8 vol% TiB2 at both 25 °C and 700 °C, and in two conditions of lamellar thickness, was measured by digital image correlation strain mapping of a remodelled Au surface speckle pattern. Such initial plasticity, not necessarily related to the presence of common stress concentrators such as hard particles or cracks, could occur at applied stresses as low as 64% of the general yield stress. For a same applied strain it was more prominent at room temperature, and located as slip and twinning parallel to, and near to or at (respect.) lamellar interfaces of all types in soft mode-oriented colonies. These stretched the full colony width and the shear strain was most intense in the centre of the colonies. Further, the most highly operative microbands of plasticity at specimen fracture were not those most active prior to yielding. The strain mapping results from polycrystalline tensile loading were further compared to those from microcompression testing of soft-mode stacks of lamellae milled from single colonies performed at the same temperatures. Combined with post-mortem transmission electron microscopy of the pillars, the initial plasticity by longitudinal dislocation glide was found to locate within 30–50 nm of the lamellar interfaces, and not at the interfaces themselves. The highly localised plasticity that precedes high cycle fatigue failure is therefore inherently related to the lamellar structure, which predetermines the locations of plastic strain accumulation, even in a single loading cycle.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Materials Science, Research group: Materials Characterization, University of Cambridge, Swiss Federal Laboratories for Materials Science and Technology
Contributors: Edwards, T. E. J., Di Gioacchino, F., Goodfellow, A. J., Mohanty, G., Wehrs, J., Michler, J., Clegg, W. J.
Number of pages: 18
Pages: 122-139
Publication date: 15 Jan 2019
Peer-reviewed: Yes
Early online date: 2018

Publication information

Journal: Acta Materialia
Volume: 163
ISSN (Print): 1359-6454
Ratings: 
  • Scopus rating (2019): SJR 3.662 SNIP 3.037
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Ceramics and Composites, Polymers and Plastics, Metals and Alloys
Keywords: Deformation twinning, Digital image correlation, Electron backscattering diffraction (EBSD), Pre-yield plasticity, Titanium aluminide
Source: Scopus
Source ID: 85055112164

Research output: Contribution to journalArticleScientificpeer-review

Transverse deformation of a lamellar TiAl alloy at high temperature by in situ microcompression

The distribution of strain in hard mode oriented lamellar stacks of the two-phase γ-TiAl/α2-Ti3Al alloy Ti-45Al-2Nb-2Mn (at.%)-0.8 vol% TiB2 was measured at several temperatures up to 633 °C by in situ micropillar compression, complemented by electron backscatter diffraction orientation mapping and digital image correlation strain mapping of a thermally stable surface Pt speckle pattern. Post-mortem transmission electron microscopy further identified the finest scale deformation structures. It was found that slip and twinning transverse to the lamellae operates within discreet bands that zigzag across the lamellar structure. The shear strain within each band is approximately constant across the pillar width. This is inconsistent with current energetic models for transverse twin formation in γ-TiAl, which assume independent, non-interacting twins. This is explained using a mathematical formulation for the stress required to operate this transverse mechanical twinning as a function of strain. This study has elucidated how the multi-scale combination of several transverse twinning systems on different {111} planes in γ-TiAl lamellae can relieve the elastic stresses generated at a lamellar interface by the primary (highest Schmid factor) twinning system. It is thought that the facilitation of this mechanism will promote the ductilisation of lamellar γ-TiAl alloys. This is crucial for an increased damage tolerance and ease of component manufacture, leading to a more widespread use of γ-TiAl alloys.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Materials Science, University of Cambridge, Swiss Federal Laboratories for Materials Science and Technology
Contributors: Edwards, T. E. J., Di Gioacchino, F., Goodfellow, A. J., Mohanty, G., Wehrs, J., Michler, J., Clegg, W. J.
Number of pages: 15
Pages: 85-99
Publication date: 1 Mar 2019
Peer-reviewed: Yes
Early online date: 27 Nov 2018

Publication information

Journal: Acta Materialia
Volume: 166
ISSN (Print): 1359-6454
Ratings: 
  • Scopus rating (2019): SJR 3.662 SNIP 3.037
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Ceramics and Composites, Polymers and Plastics, Metals and Alloys
Keywords: Deformation twinning, Digital image correlation, Electron backscattering diffraction (EBSD), Scanning transmission electron microscopy, Titanium aluminide polysynthetically twinned crystal (PST)
Source: Scopus
Source ID: 85058779138

Research output: Contribution to journalArticleScientificpeer-review

3-D Numerical Modeling of AC Losses in Multifilamentary MgB2 Wires

Due to their high current carrying capacity, round geometry and low cost, MgB2 wires are promising candidates for realizing high power cables. However, their operating temperature comprised between 4.2 K and 25 K makes AC losses a critical issue for those cables. In order to optimize the cable architecture for minimizing AC losses, one must be able to predict them quite accurately. As a first step in this direction, we addressed the numerical computation of a single multi-filamentary MgB2 wire that forms the basic element of a high current cable. The wire under consideration has 36 twisted MgB2 filaments disposed on three concentric layers and embedded in a pure nickel matrix. An initial comparison between 2-D and 3-D finite elements was performed in order to justify the need of a full 3-D model, without which coupling losses in the matrix cannot be modeled properly. This is of prime importance since coupling loss is the dominant loss mechanism at high applied fields. Then, simulations of simpler geometries (6- and 18- filament wires) submitted to various transport currents and/or applied fields were performed to identify trends in AC losses and find the best numerical tools for scaling up simulations to the full 36-filament case. The complexity of the model was increased progressively, starting with MgB2 filaments in air matrix, then adding electrical conductivity and magnetic properties in the nickel matrix.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Research area: Electromagnetics, Department of Electrical Engineering, G2Elab/Institut Néel, Polytechnique Montréal, Cedrat S.A. 15 Chemin de Malacher-Inovallé, Nexans France
Contributors: Escamez, G., Sirois, F., Lahtinen, V., Stenvall, A., Badel, A., Tixador, P., Ramdane, B., Meunier, G., Perrin-Bit, R., Bruzek, C. É.
Publication date: 1 Apr 2016
Peer-reviewed: Yes
Early online date: 2016

Publication information

Journal: IEEE Transactions on Applied Superconductivity
Volume: 26
Issue number: 3
Article number: 4701907
ISSN (Print): 1051-8223
Ratings: 
  • Scopus rating (2016): CiteScore 1.42 SJR 0.398 SNIP 1.132
Original language: English
ASJC Scopus subject areas: Electrical and Electronic Engineering, Condensed Matter Physics, Electronic, Optical and Magnetic Materials
Keywords: AC losses, FEM modelling, MgB2, power cable
Source: Scopus
Source ID: 84963878465

Research output: Contribution to journalArticleScientificpeer-review

Development of efficient electrically pumped nanolasers based on InAlGaAs tunnel junction

We propose and experimentally demonstrate a metallo-dielectric nanolasers utilizing an InAlGaAs tunnel junction for efficient carrier injection, which reduce the complexity when optimizing the metal contact, and reduces the device resistance.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Photonics, Research group: ORC, University of California San Diego
Contributors: Fang, C. Y., Vallini, F., Amili, A. E., Tukiainen, A., Lyytikäinen, J., Guina, M., Fainman, Y.
Publication date: 2018

Host publication information

Title of host publication: CLEO : Science and Innovations, CLEO_SI 2018
Publisher: OSA - The Optical Society
ISBN (Electronic): 9781557528209
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Mechanics of Materials
Source: Scopus
Source ID: 85048984466

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Evaluating transparent liquid screen overlay as a haptic conductor: Method of enhancing touchscreen based user interaction by a transparent deformable liquid screen overlay

In line with our previous work, this research focuses on a method for attenuating acoustic components (noise) while providing enhanced vibrotactile feedback signals on mobile devices using, deformable touchscreen overlays. Traditional mechanism of providing tactile feedback to the fingertip via a flat rigid touchscreen is limited due to the dampening of the mechanoreceptors which are sensitive to static deformation and lie at the tips of the intermediate ridges in the epidermal-dermal junction. This tactile mechanism becomes useless when the fingertip acts against a ridged surface (chemically strengthened alkali-aluminosilicate glass). Furthermore, the actuation provided by most devices is indirect with little or no mediation mechanism, which results in filtering various signal frequencies, loss of signal intensity as well as creating acoustic noise. The resulting haptic signal is considerably inefficient and incongruent to the applied signal, which was designed to stimulate user skin contact. To resolve these issues we developed a unique transparent screen overlay conductor which contains an oil based composition (a low viscosity inert nonconductive liquid), that acts as a soft deformable interaction point, enhancing the ratio between tactile signals and the acoustic components, provided by haptic actuators. Using surface mounted and embedded actuators to the overlay, while being attached to an ExoPC Slate, we measured haptic signal to noise correlation, as well as signal efficiency and strength over multiple frequencies and concluded that the haptic conductor was able to limit auditory noise and mediate tactile signals more efficiently than traditional rigid glass based surfaces.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Augmented Human Activities (AHA), Fukoku-Rubber Co.
Contributors: Farooq, A., Evreinov, G., Raisamo, R., Takahata, D.
Publication date: 31 Dec 2015

Host publication information

Title of host publication: 2015 IEEE SENSORS - Proceedings
Publisher: Institute of Electrical and Electronics Engineers Inc.
Article number: 7370186
ISBN (Electronic): 9781479982028
ASJC Scopus subject areas: Instrumentation, Electronic, Optical and Magnetic Materials, Spectroscopy, Electrical and Electronic Engineering
Keywords: haptic signal mediation, haptics user interface, Liquid transparent screen overlay, piezoelectric and voice coil actuators, vibrotactile mechano-transduction
Source: Scopus
Source ID: 84963615224

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Development of MQXF: The Nb3Sn Low-β Quadrupole for the HiLumi LHC

The High Luminosity (HiLumi) Large Hadron Collider (LHC) project has, as the main objective, to increase the LHC peak luminosity by a factor five and the integrated luminosity by a factor ten. This goal will be achieved mainly with a new interaction region layout, which will allow a stronger focusing of the colliding beams. The target will be to reduce the beam size in the interaction points by a factor of two, which requires doubling the aperture of the low-β (or inner triplet) quadrupole magnets. The use of Nb3Sn superconducting material and, as a result, the possibility of operating at magnetic field levels in the windings higher than 11 T will limit the increase in length of these quadrupoles, called MQXF, to acceptable levels. After the initial design phase, where the key parameters were chosen and the magnet's conceptual design finalized, the MQXF project, a joint effort between the U.S. LHC Accelerator Research Program and the Conseil Europeén pour la Recherche Nucleaíre (CERN), has now entered the construction and test phase of the short models. Concurrently, the preparation for the development of the full-length prototypes has been initiated. This paper will provide an overview of the project status, describing and reporting on the performance of the superconducting material, the lessons learnt during the fabrication of superconducting coils and support structure, and the fine tuning of the magnet design in view of the start of the prototyping phase.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Electrical Engineering, Research area: Electromagnetics, European Organization for Nuclear Research, Fermi National Accelerator Laboratory, Brookhaven National Laboratory, Lawrence Berkeley National Laboratory, Istituto Nazionale Di Fisica Nucleare, Frascati
Contributors: Ferracin, P., Ambrosio, G., Anerella, M., Ballarino, A., Bajas, H., Bajko, M., Bordini, B., Bossert, R., Cheng, D. W., Dietderich, D. R., Chlachidze, G., Cooley, L., Felice, H., Ghosh, A., Hafalia, R., Holik, E., Izquierdo Bermudez, S., Fessia, P., Grosclaude, P., Guinchard, M., Juchno, M., Krave, S., Lackner, F., Marchevsky, M., Marinozzi, V., Nobrega, F., Oberli, L., Pan, H., Perez, J. C., Prin, H., Rysti, J., Rochepault, E., Sabbi, G., Salmi, T., Schmalzle, J., Sorbi, M., Sequeira Tavares, S., Todesco, E., Wanderer, P., Wang, X., Yu, M.
Publication date: 1 Jun 2016
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Applied Superconductivity
Volume: 26
Issue number: 4
Article number: 4000207
ISSN (Print): 1051-8223
Ratings: 
  • Scopus rating (2016): CiteScore 1.42 SJR 0.398 SNIP 1.132
Original language: English
ASJC Scopus subject areas: Electrical and Electronic Engineering, Condensed Matter Physics, Electronic, Optical and Magnetic Materials
Keywords: High Luminosity LHC, Interaction Regions, Low-β Quadrupoles
Source: Scopus
Source ID: 84962432718

Research output: Contribution to journalArticleScientificpeer-review

Full-field mode sorter using two optimized phase transformations for high-dimensional quantum cryptography

High-dimensional encoding schemes have emerged as a novel way to perform quantum information tasks. For high dimensionality, temporal and transverse spatial modes of photons are the two paradigmatic degrees of freedom commonly used in such experiments. Nevertheless, general devices for multi-outcome measurements are still needed to take full advantage of the high-dimensional nature of encoding schemes. We propose a general full-field mode sorting scheme consisting of only up to two optimized phase elements based on evolutionary algorithms that allows for joint sorting of azimuthal and radial modes. We further study the performance of our scheme through simulations in the context of high-dimensional quantum cryptography, where sorting in different mutually unbiased bases and high-fidelity measurement schemes are crucial.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Physics, Austrian Academy of Sciences, University of Ottawa, Canada, University of Ulm Medical Center, Centro S3, Max Planck Institute for the Science of Light, Friedrich-Alexander-Universität Erlangen-Nürnberg
Contributors: Fickler, R., Bouchard, F., Giese, E., Grillo, V., Leuchs, G., Karimi, E.
Number of pages: 7
Publication date: 2020
Peer-reviewed: Yes

Publication information

Journal: Journal of Optics (United Kingdom)
Volume: 22
Issue number: 2
Article number: 024001
ISSN (Print): 2040-8978
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Atomic and Molecular Physics, and Optics
Keywords: mode demultiplexing high-dimensional quantum information, quantum cryptography, transverse spatial modes
Electronic versions: 
Source: Scopus
Source ID: 85079689477

Research output: Contribution to journalArticleScientificpeer-review

Picosecond MOPA with ytterbium doped tapered double clad fiber

The powerful picosecond master oscillator - power amplifier (MOPA) with double clad ytterbium doped tapered fiber as a buster amplifier has been demonstrated in the presented paper. The developed MOPA has 60ps pulses with 0.3mJ pulse energy and 5MW peak power.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Research group: Ultrafast and intense lasers, Photonics, Research group: Nanophotonics, Ampliconyx Ltd, Institute of Radio Engineering and Electronics of the Russian Academy of Sciences
Contributors: Filippov, V., Vorotynskii, A., Noronen, T., Gumenyuk, R., Chamorovskii, Y., Golant, K.
Number of pages: 6
Publication date: 2017

Host publication information

Title of host publication: Fiber Lasers XIV : Technology and Systems
Volume: 10083
Publisher: SPIE
Article number: 100831H
ISBN (Electronic): 9781510606074

Publication series

Name: Proceedings of SPIE
Publisher: SPIE
No.: 10083
ISSN (Print): 0277-786X
ISSN (Electronic): 1996-756X
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Computer Science Applications, Applied Mathematics, Electrical and Electronic Engineering
Keywords: Fiber laser, Picosecond laser, Ultrafast laser
Source: Scopus
Source ID: 85019465842

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Anisotropic ultra-large mode area Yb-doped tapered double clad fiber for ultrafast amplifiers

The anisotropic ytterbium doped tapered double clad fiber with 95 μm mode field diameter is experimentally demonstrated. The high power picosecond master oscillator - power amplifier with 70 W average power pulses is developed.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Photonics, Ampliconyx Ltd, Institute of Radio Engineering and Electronics of the Russian Academy of Sciences, St. Petersburg State Polytechnical University
Contributors: Filippov, V., Noronen, T., Gumenyuk, R., Chamorovskii, Y., Golant, K., Odnoblyudov, M.
Publication date: 2017

Host publication information

Title of host publication: Advanced Solid State Lasers 2017 : Nagoya, Aichi Japan 1–5 October 2017
Volume: Part F75-ASSL 2017
Publisher: The Optical Society; OSA
Article number: JTu2A.51
ISBN (Electronic): 978-0-9600380-7-7
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Mechanics of Materials
Source: Scopus
Source ID: 85039147555

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

FEM for directly coupled magneto-mechanical phenomena in electrical machines

A directly coupled magneto-mechanical model is proposed for simulating the effect of the magnetostriction and electromagnetic stress in iron. The model is based on the general balance laws of electromagnetism, mechanics, and continuum thermodynamics. It is implemented in 2-D by using a conforming finite element method for the magnetic vector potential and the displacement field. The method is applied to two different types of induction machines.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Aalto University
Contributors: Fonteyn, K., Belahcen, A., Kouhia, R., Rasilo, P., Arkkio, A.
Number of pages: 4
Pages: 2923-2926
Publication date: Aug 2010
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Magnetics
Volume: 46
Issue number: 8
ISSN (Print): 0018-9464
Ratings: 
  • Scopus rating (2010): SJR 0.712 SNIP 1.134
Original language: English
ASJC Scopus subject areas: Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials
Keywords: electromagnetic stress tensor, finite element analysis, Magneto-mechanical coupling, magnetostriction
Source: Scopus
Source ID: 77954840624

Research output: Contribution to journalArticleScientificpeer-review

Optical fiber amplifier with spectral compression elements for high-power laser pulse generation

We report main features of spectral compression of parabolic pulses in nonlinear optical fibers. It is shown that the variational analysis correctly describes evolution of pulse parameters during spectral compression. The model of cascade amplifier system employing spectral compression is developed to achieve superior spectral densities. The proposed configuration is promising as optical pulse preamplifier for operation in the high-energy pulse laser systems.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Optoelectronics Research Centre, University de Mons, Ulyanovsk State University, Optoelectronic Research Center
Contributors: Fotiadi, A. A., Korobko, D. A., Okhotnikov, O. G., Zolotovskii, I. O.
Publication date: 2016

Host publication information

Title of host publication: Nonlinear Optics and its Applications IV
Volume: 9894
Publisher: SPIE
Article number: 989411
ISBN (Electronic): 9781510601390

Publication series

Name: Proceedings of SPIE
Volume: 9894
ISSN (Print): 0277-786X
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Computer Science Applications, Electrical and Electronic Engineering, Applied Mathematics
Keywords: Fiber optics amplifiers, high-power laser pulses, nonlinear spectral compression, phase self-modulation
Source: Scopus
Source ID: 84985911601

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Simultenious binary hash and features learning for image retrieval

Content-based image retrieval systems have plenty of applications in modern world. The most important one is the image search by query image or by semantic description. Approaches to this problem are employed in personal photo-collection management systems, web-scale image search engines, medical systems, etc. Automatic analysis of large unlabeled image datasets is virtually impossible without satisfactory image-retrieval technique. It's the main reason why this kind of automatic image processing has attracted so much attention during recent years. Despite rather huge progress in the field, semantically meaningful image retrieval still remains a challenging task. The main issue here is the demand to provide reliable results in short amount of time. This paper addresses the problem by novel technique for simultaneous learning of global image features and binary hash codes. Our approach provide mapping of pixel-based image representation to hash-value space simultaneously trying to save as much of semantic image content as possible. We use deep learning methodology to generate image description with properties of similarity preservation and statistical independence. The main advantage of our approach in contrast to existing is ability to fine-tune retrieval procedure for very specific application which allow us to provide better results in comparison to general techniques. Presented in the paper framework for data- dependent image hashing is based on use two different kinds of neural networks: convolutional neural networks for image description and autoencoder for feature to hash space mapping. Experimental results confirmed that our approach has shown promising results in compare to other state-of-the-art methods.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Department of Signal Processing, Research group: Computational Imaging-CI, Don State Technical University, Univ of Texas at San Antonio
Contributors: Frantc, V. A., Makov, S. V., Voronin, V. V., Marchuk, V. I., Semenishchev, E. A., Egiazarian, K. O., Agaian, S.
Publication date: 2016

Host publication information

Title of host publication: Mobile Multimedia/Image Processing, Security, and Applications 2016
Publisher: SPIE
Article number: 986902
ISBN (Electronic): 9781510601109

Publication series

Name: SPIE Conference Proceedings
Volume: 9869
ISSN (Print): 0277-786X
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Computer Science Applications, Applied Mathematics, Electrical and Electronic Engineering
Keywords: autoencoder, content{based image retrieval, deep convolutional neural network, semantic hashing
Source: Scopus
Source ID: 84991480411

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Reliability of ACA interconnections on microvia HDI PCBs in thermal cycling conditions

New packaging technologies require new high density substrates. In built up high density interconnect (HDI) printed circuit boards (PCB) high density is achieved by using built up microvia layers. Such HDI PCBs may be used in many applications. In flip chip technology a bare chip is attached directly to a substrate which enables very high density and requires often also HDI PCBs. Anisotropic conductive adhesives (ACA) are especially well suited interconnection materials for high density flip chip applications. In this study the reliability of flip chip ACA attachments on several different HDI PCBs was studied. The PCBs had similar core layers, but the microvia layers of the PCBs were different. Test chips were attached on these PCBs using an ACA film (ACF). The reliability of the interconnections was tested using fast thermal cycling between the temperatures of -40?C and 125?C. Several failures were seen with all PCB materials during the 2,000 cycles of testing. The differences in the reliability of the different microvia layers were found to be relatively small and the microvia layer composition did not seem to be critical for the thermal cycling reliability of the ACF interconnections.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Department of Electrical Engineering, Research area: Reliability
Contributors: Frisk, L., Lahokallio, S., Kiilunen, J.
Publication date: 5 Jun 2016

Host publication information

Title of host publication: IMAPS Nordic Annual Conference 2016 Proceedings
Publisher: IMAPS-International Microelectronics and Packaging Society
Editor: Kutilainen, J.
ISBN (Electronic): 9781510827226
ASJC Scopus subject areas: Electrical and Electronic Engineering, Engineering (miscellaneous), Electronic, Optical and Magnetic Materials
Keywords: Anisotropic conductive adhesive, Flip chip, High density interconnect, Printed circuit board, Reliability, Thermal cycling
Source: Scopus
Source ID: 84988001295

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Machine learning for adaptive bilateral filtering

We describe a supervised learning procedure for estimating the relation between a set of local image features and the local optimal parameters of an adaptive bilateral filter. A set of two entropy-based features is used to represent the properties of the image at a local scale. Experimental results show that our entropy-based adaptive bilateral filter outperforms other extensions of the bilateral filter where parameter tuning is based on empirical rules. Beyond bilateral filter, our learning procedure represents a general framework that can be used to develop a wide class of adaptive filters.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Department of Signal Processing, Research group: Computational Imaging-CI, Signal Processing Research Community (SPRC), NVIDIA
Contributors: Frosio, I., Egiazarian, K., Pulli, K.
Publication date: 2015

Host publication information

Title of host publication: Image Processing: Algorithms and Systems XIII
Volume: 9399
Publisher: SPIE
Article number: 939908
ISBN (Print): 9781628414899

Publication series

Name: Proceedings of SPIE - The International Society for Optical Engineering
Publisher: The International Society for Optical Engineering
ISSN (Print): 0277-786X
ISSN (Electronic): 1996-756X
ASJC Scopus subject areas: Applied Mathematics, Computer Science Applications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Keywords: Adaptive bilateral filter, Denoising, Machine learning, Optimization, Training
Source: Scopus
Source ID: 84928485491

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Single-source multibattery solar charger: Case study and implementation issues

In this paper, design process and functionality of a portable single-panel dual-battery solar charger prototype are presented, achieving energy density of 571Whkg-1 during a typical 3-day infantry mission. The device may instantaneously charge up to two Li-ion MR-2791 batteries, supporting plug-and-play operation. The system consists of a lightweight custom solar panel, based on 20% efficient monocrystalline photovoltaics, and an intelligent power processing module. The panel contains eight transparent polymer-encapsulated and camouflaged series-connected six solar cell packs with antiparallel diodes, allowing partial shading operation. The power processing module consists of two synchronous current-mode-controlled buck converters, digital signal processor, and a microcontroller, supporting both maximum power point tracking of the solar panel with partial shading detection and multimode charging of Li-ion packs while instantaneously communicating with the batteries. Power management algorithmic design is presented, based on ensuring system stability while supporting the required operation modes. System implementation stages and underlying issues are thoroughly discussed, and utilized hardware components are presented in detail. Experimental results of system testing under real outdoor conditions are presented to demonstrate the device functionality and energy yield capabilities.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Electrical Engineering, Research area: Power engineering, Smart Energy Systems (SES), Hybrid Energy Sources Laboratory
Contributors: Gadelovits, S., Sitbon, M., Suntio, T., Kuperman, A.
Number of pages: 13
Pages: 1916-1928
Publication date: 25 Nov 2015
Peer-reviewed: Yes

Publication information

Journal: Progress in Photovoltaics: Research and Applications
Volume: 23
Issue number: 12
ISSN (Print): 1062-7995
Ratings: 
  • Scopus rating (2015): CiteScore 7.31 SJR 2.724 SNIP 3.409
Original language: English
ASJC Scopus subject areas: Renewable Energy, Sustainability and the Environment, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Keywords: Energy density, Li-ion battery, Partial shading, Portable system, Solar charger

Research output: Contribution to journalArticleScientificpeer-review

Coherence of Supercontinuum Light

Supercontinuum (SC) light fields are characterized by broadband spectra that may extend from ultraviolet to near-infrared. Such SC fields can be generated by nonlinear processes in solid-state bulk media and liquids, or in optical fibers. In the latter case, SC pulse trains with high spatial coherence can be produced, which however may feature widely different spectral and temporal properties depending on the excitation conditions. In this review, we consider the coherence properties of SC pulses using the second-order coherence theory of nonstationary light. We begin with an overview of SC generation and explain how different nonlinear processes give rise to variable coherence properties. After a brief review of the coherence theory of nonstationary light, we show how second-order correlation functions in both time and frequency domains can be constructed from numerical simulations of ensembles of individual pulses. Two types of convenient modal representations of these correlation functions are presented, and a connection to the widely used "first-order" spectral coherence function is made. We then consider several interferometric techniques that have been used to measure this first-order coherence function, and discuss methods for experimental determination of the second-order correlations. Finally, some conclusions are drawn and certain as-yet unresolved questions regarding the coherence of SC are outlined.

General information

Publication status: Published
MoE publication type: A3 Part of a book or another research book
Organisations: Department of Physics, Research group: Nonlinear Fiber Optics, Research area: Optics
Contributors: Genty, G., Friberg, A. T., Turunen, J.
Publication date: 2016

Host publication information

Title of host publication: Progress in Optics
Volume: 61
Publisher: Elsevier
ISBN (Print): 978-0-12-804699-9

Publication series

Name: Progress in Optics
ISSN (Print): 0079-6638
ASJC Scopus subject areas: Surfaces and Interfaces, Electronic, Optical and Magnetic Materials
Keywords: Coherence, Interferometry, Modes, Pulses, Supercontinuum

Bibliographical note

JUFOID=65575

Source: Scopus
Source ID: 84960194642

Research output: Chapter in Book/Report/Conference proceedingChapterScientificpeer-review

Towards universal enrichment nanocoating for IR-ATR waveguides

Polymer multilayered nanocoating capable of concentrating various chemical substances at IR-ATR waveguide surfaces is described. The coating affinity to an analyte played a pivotal role in sensitivity enhancement of the IR-ATR measurements, since the unmodified waveguide did not show any analyte detection.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Frontier Photonics, Clemson University, School of Materials Science and Engineering/COMSET, University of Delaware, Massachusetts Institute of Technology
Contributors: Giammarco, J., Zdyrko, B., Petit, L., Musgraves, J. D., Hu, J., Agarwal, A., Kimerling, L., Richardson, K., Luzinov, I.
Number of pages: 3
Pages: 9104-9106
Publication date: 28 Aug 2011
Peer-reviewed: Yes

Publication information

Journal: Chemical Communications
Volume: 47
Issue number: 32
ISSN (Print): 1359-7345
Ratings: 
  • Scopus rating (2011): CiteScore 5.96 SJR 2.889 SNIP 1.326
Original language: English
ASJC Scopus subject areas: Catalysis, Electronic, Optical and Magnetic Materials, Ceramics and Composites, Chemistry(all), Surfaces, Coatings and Films, Metals and Alloys, Materials Chemistry
Source: Scopus
Source ID: 79961012632

Research output: Contribution to journalArticleScientificpeer-review

Dilute nitride SOAs for high-speed data processing in variable temperature conditions

We present the first experimental study of a Dilute Nitride SOA with high-speed gain dynamics and attractive thermal characteristics as a data processing element at 10Gb/s and at different operating temperatures.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Frontier Photonics, Optoelectronics Research Centre, Research group: Semiconductor Technology and Applications, Aristotle University of Thessaloniki, School of Electrical and Computer Engineering, National Technical University of Athens
Contributors: Giannoulis, G., Korpijärvi, V. M., Iliadis, N., Mäkelä, J., Viheriälä, J., Apostolopoulos, D., Guina, M., Avramopoulos, H.
Publication date: 13 Mar 2015

Host publication information

Title of host publication: Optical Fiber Communication Conference, OFC 2015
Publisher: OSA - The Optical Society
ISBN (Print): 9781557529374
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Computer Networks and Communications, Instrumentation, Atomic and Molecular Physics, and Optics

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Bringing High-Performance GaInNAsSb/GaAs SOAs to True Data Applications

We experimentally demonstrate the high-speed data processing capabilities of a GaInNAsSb semiconductor optical amplifier operating at 1.55 μm. The investigated structure exhibits good thermal characteristics and fast gain dynamics with 10%-90% recovery time of 55 ps. Successful wavelength conversion of 10-Gb/s signals is reported. A maximum power penalty of <2.4 dB for return to zero formatting and of 1.9 dB for nonreturn to zero is demonstrated.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Optoelectronics Research Centre, Research group: Semiconductor Technology and Applications, Research group: Nanophotonics, Frontier Photonics, Photonics Research Communications Laboratory, National Technological University of Athens
Contributors: Giannoulis, G., Korpijärvi, V., Iliadis, N., Mäkelä, J., Viheriälä, J., Apostolopoulos, D., Guina, M., Avramopoulos, H.
Number of pages: 4
Pages: 1691-1694
Publication date: 15 Aug 2015
Peer-reviewed: Yes

Publication information

Journal: IEEE Photonics Technology Letters
Volume: 27
Issue number: 16
Article number: 7113825
ISSN (Print): 1041-1135
Ratings: 
  • Scopus rating (2015): CiteScore 2.62 SJR 1.19 SNIP 1.254
Original language: English
ASJC Scopus subject areas: Electrical and Electronic Engineering, Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials
Keywords: dilute nitrides, Photonic integration, semiconductor optical amplifier (SOA), wavelength conversion
Source: Scopus
Source ID: 84937146617

Research output: Contribution to journalArticleScientificpeer-review

Better understanding of the role of SiO2, P2O5 and Al2O3 on the spectroscopic properties of Yb3+ doped silica sol-gel glasses

Yb3+ doped silica sol-gel glass powders were prepared with different concentrations of SiO2, Al2O3 and P2O5 in order to understand the impact of the glass composition on the Yb3+ emission properties. In this paper, we clearly show that not only the Al/P ratio but also the SiO2 content have an impact on the Yb3+ spectroscopic properties. Our results provide new insight on the real impact of the composition on the spectroscopic properties of Yb3+ doped sol-gels: we demonstrate that an increase in the Al2O3 content at the expense of P2O5 leads to an increase in the intensity of the emission at 1000nm of the Yb3+ ions whereas an increase in the SiO2 content decreases it. We clearly showed that the inexpensive sol-gel approach can be easily used when investigating new Yb3+ doped silica glasses.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Photonics, Research group: Nanophotonics, Faculty of Biomedical Sciences and Engineering, Research group: Biomaterials and Tissue Engineering Group, Research group: Photonics Glasses, Institut de Chimie de la Matiere Condensee de Bordeaux, Turun Yliopisto/Turun Biomateriaalikeskus
Contributors: Glorieux, B., Salminen, T., Massera, J., Lastusaari, M., Petit, L.
Pages: 46-51
Publication date: 2018
Peer-reviewed: Yes
Early online date: 2017

Publication information

Journal: Journal of Non-Crystalline Solids
Volume: 482
ISSN (Print): 0022-3093
Ratings: 
  • Scopus rating (2018): CiteScore 2.7 SJR 0.689 SNIP 1.186
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Ceramics and Composites, Condensed Matter Physics, Materials Chemistry
Keywords: Silica glass, Sol-gel, Spectroscopic properties, Yb doping
Source: Scopus
Source ID: 85037629421

Research output: Contribution to journalArticleScientificpeer-review

Silver sulfide nanoclusters and the superatom model

The superatom model of electron-shell closings has been widely used to explain the stability of noble-metal nanoclusters of few nanometers, including thiolate-protected Au and Ag nanoclusters. The presence of core sulfur atoms in silver sulfide (Ag-S) nanoclusters renders them a class of clusters with distinctive properties as compared to typical noble-metal clusters. Here, it is natural to ask whether the superatom model is still applicable for the Ag-S nanoclusters with mixed metal and nonmetal core atoms. To address this question, we applied density functional simulations to analyze a series of Ag-S nanoclusters: Ag14S(SPh)12(PPh3)8, Ag14(SC6H3F2)12(PPh3)8, Ag70S16(SPh)34(PhCO2)4(triphos)4, and [Ag123S35(StBu)50]3+. We observed that superatomic orbitals are still present in the conduction band of these Ag-S clusters where the cluster cores comprise mostly silver atoms. Our Bader charge analysis illustrates that thiolates play a significant role in withdrawing charge (electron density) from the core Ag atoms. The simulated optical absorption properties of the selected Ag-S clusters reflect the substantial band gaps associated with typical molecular orbitals on both sides. Apart from Ag14S(SPh)12(PPh3)8, which has a central sulfur atom in the cluster core, superatomic orbitals of the Ag-S clusters can have contributions for individual transitions in the conduction band.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Physics, Research group: Materials and Molecular Modeling, Computational Science X (CompX), University of Jyväskylä, Departments of Physics and Chemistry
Contributors: Goh, J., Malola, S., Häkkinen, H., Akola, J.
Number of pages: 8
Pages: 1583-1590
Publication date: 22 Jan 2015
Peer-reviewed: Yes

Publication information

Journal: Journal of Physical Chemistry C
Volume: 119
Issue number: 3
ISSN (Print): 1932-7447
Ratings: 
  • Scopus rating (2015): CiteScore 4.68 SJR 1.886 SNIP 1.246
Original language: English
ASJC Scopus subject areas: Physical and Theoretical Chemistry, Electronic, Optical and Magnetic Materials, Surfaces, Coatings and Films, Energy(all)
Source: Scopus
Source ID: 84921476515

Research output: Contribution to journalArticleScientificpeer-review

Superatom Model for Ag-S Nanocluster with Delocalized Electrons

Several Ag–S nanoclusters where the cluster core comprises mixed metal (main component) and sulfur atoms show superatomic orbitals in the conduction band edge. However, there are no superatomic states, i.e., delocalized electrons, in the valence band, and the clusters in question can be labeled as “zerovalent”. We show here an example of an Ag–S cluster which fulfills the superatom model and has delocalized electrons: The recently synthesized and characterized [Ag62S12(StBu)32]2+ cluster has four delocalized valence electrons based on a simple counting rule, and we compare it to the zerovalent cluster [Ag62S13(StBu)32]4+. Our electronic structure analysis confirms the existence of superatomic states in the valence and conduction bands, but the locations of these states do not agree completely with the conventional prediction based on the spherical Jellium model. [Ag62S12(StBu)32]2+ displays the 1S2 electronic shell closure at the Fermi energy instead of the 1S21P2 configuration as suggested by its electron count. This shift of energy levels and electron shell closing has been introduced by the core–shell structure of the cluster. Our optical absorption simulation can reproduce the features observed in the experiments, and we assign these features to the transitions involving superatomic states within the conduction band.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Physics, Research group: Materials and Molecular Modeling, Computational Science X (CompX), COMP Centre of Excellence, Department of Applied Physics, Aalto University
Contributors: Goh, J. Q., Akola, J.
Number of pages: 8
Pages: 21165-21172
Publication date: 10 Sep 2015
Peer-reviewed: Yes
Early online date: 19 Aug 2015

Publication information

Journal: Journal of Physical Chemistry C
Volume: 119
Issue number: 36
ISSN (Print): 1932-7447
Ratings: 
  • Scopus rating (2015): CiteScore 4.68 SJR 1.886 SNIP 1.246
Original language: English
ASJC Scopus subject areas: Physical and Theoretical Chemistry, Electronic, Optical and Magnetic Materials, Surfaces, Coatings and Films, Energy(all)
Source: Scopus
Source ID: 84941254956

Research output: Contribution to journalArticleScientificpeer-review

Geometric Structure and Chemical Ordering of Large AuCu Clusters: A Computational Study

Understanding the structure and composition of nanosized gold-copper (AuCu) clusters is crucial for designing an effective AuCu catalyst. Global optimization of AuCu clusters using atomistic force fields is a viable solution for clusters with at least a few nm sizes, because of its fast computation. Here we develop an atomistic many-body potential for AuCu on the basis of the second-moment approximation to the tight-binding model. We show that our potential is in good agreement with density-functional theory calculations, and use it to study the structure and chemical ordering of clusters of sizes up to ∼4 nm by means of global optimization searches. We show that the clusters present a surface enrichment in Au, while subsurface and central sites are enriched in Cu. Surface enrichment in Au and center enrichment in Cu are stronger in icosahedra. Surface Cu atoms prefer terrace sites on (111) facets. Both atomistic and DFT calculations show that L10 and L12 ordered phases are not favorable, even at their ideal compositions for these sizes, because of the tendency of Au to surface segregation. The stability range of icosahedral structures is wider in AuCu nanoalloys than in Au and Cu pure clusters.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Physics, COMP Centre of Excellence, Department of Applied Physics, Aalto University, Aalto University, Università di Genova
Contributors: Goh, J., Akola, J., Ferrando, R.
Number of pages: 8
Pages: 10809-10816
Publication date: 25 May 2017
Peer-reviewed: Yes

Publication information

Journal: Journal of Physical Chemistry C
Volume: 121
Issue number: 20
ISSN (Print): 1932-7447
Ratings: 
  • Scopus rating (2017): CiteScore 4.58 SJR 2.135 SNIP 1.133
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Energy(all), Physical and Theoretical Chemistry, Surfaces, Coatings and Films
Source: Scopus
Source ID: 85016919329

Research output: Contribution to journalArticleScientificpeer-review

The effects of laser patterning 10CeTZP-Al2O3 nanocomposite disc surfaces: Osseous differentiation and cellular arrangement in vitro

Customized square grid arrangements of different groove depths (1.0, 1.5 and 3.0 μm) and separations (10 and 30 μm) were successfully laser patterned, using a nanosecond pulsed fibre laser, on the surface of 10 mol% ceria-stabilized zirconia and alumina (10CeTZP-Al2O3) nanocomposite discs (diameter: 10 mm; thickness: 1.5 mm). The patterned surfaces and the in vitro biological response of osteoblasts (SAOS-2) towards them were thoroughly analysed. In terms of composition, the laser treatment was found to cause superficial monoclinic-tetragonal zirconia phase transformation and alumina evaporation. In vitro, the most effective grid configuration for osseous differentiation was found to be 1.5 μm groove depth and 10 μm groove separation, and confocal microscopy revealed that the cells show a tendency to be sorted as groove depth increases. It is thought that custom-made patterns could be produced to guide cell attachment in vivo, which could favour implant integration and reduce healing time.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Materials Science, Mechanical Engineering and Industrial Systems, Nanoker Research, Universidad de Oviedo
Contributors: Goyos-Ball, L., Prado, C., Díaz, R., Fernández, E., Ismailov, A., Kumpulainen, T., Levänen, E., Torrecillas, R., Fernández, A.
Pages: 9472-9478
Publication date: Jun 2018
Peer-reviewed: Yes
Early online date: 2018

Publication information

Journal: Ceramics International
Volume: 44
Issue number: 8
ISSN (Print): 0272-8842
Ratings: 
  • Scopus rating (2018): CiteScore 3.5 SJR 0.888 SNIP 1.297
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Ceramics and Composites, Process Chemistry and Technology, Surfaces, Coatings and Films, Materials Chemistry
Keywords: Alumina, Cellular arrangement, Ceramic nanocomposite, Laser patterning, Osseous differentiation, Zirconia
Source: Scopus
Source ID: 85042621677

Research output: Contribution to journalArticleScientificpeer-review

Fundamental gaps of quantum dots on the cheap

We show that the fundamental gaps of quantum dots can be accurately estimated at the computational effort of a standard ground-state calculation supplemented with a non-self-consistent step of negligible cost, all performed within density-functional theory at the level of the local-density approximation.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Physics, Research group: Quantum Control and Dynamics, Universita degli Studi di Modena e Reggio Emilia, Centro S3
Contributors: Guandalini, A., Rozzi, C. A., Räsänen, E., Pittalis, S.
Publication date: 25 Mar 2019
Peer-reviewed: Yes

Publication information

Journal: Physical Review B
Volume: 99
Issue number: 12
Article number: 125140
ISSN (Print): 2469-9950
Ratings: 
  • Scopus rating (2019): SJR 1.811 SNIP 1.025
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Source: Scopus
Source ID: 85064152482

Research output: Contribution to journalArticleScientificpeer-review

Quantum-well Laser Emitting at 1.2 μm-1.3 μm Window Monolithically Integrated on Ge Substrate

We report a quantum-well laser diode monolithically integrated on Ge substrate. The gain is provided by two GaInNAsSb/GaAs quantum-wells with emission at 1.2 μm-1.3 μm. The diode exhibits continuous-wave operation with mW-level output power at room temperature.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Photonics, Research group: ORC
Contributors: Guina, M., Isoaho, R., Viheriälä, J., Aho, A., Aho, A., Tukiainen, A.
Number of pages: 3
Pages: 1-3
Publication date: 24 Apr 2018

Host publication information

Title of host publication: 43rd European Conference on Optical Communication, ECOC 2017
Publisher: IEEE
ISBN (Electronic): 9781538656242
ASJC Scopus subject areas: Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials
Source: Scopus
Source ID: 85046978554

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

All-fiber, high-power, picosecond Yb double clad tapered fiber amplifier

We demonstrate picosecond all-fiber system utilizing Yb-doped tapered power amplifier. The system is capable of producing 6 ps pulses with average power of 60 W and peak power of 0.4 MW. © 2014 IEEE.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Research group: Ultrafast and intense lasers, Optoelectronics Research Centre, Tampere University of Technology, Frontier Photonics, Optoelectronics Research Centre, Tampere University of Technology, Institute of Radio Engineering and Electronics, Russian Academy of Sciences (IRE RAS), Russian Academy of Sciences
Contributors: Gumenyuk, R., Filippov, V., Vorotinskii, A., Okhotnikov, O. G., Chamorovskii, Y., Golant, K.
Publication date: 2014

Host publication information

Title of host publication: Proceedings - 2014 International Conference Laser Optics, LO 2014
Publisher: IEEE
Article number: 6886471
ISBN (Print): 978-1-4799-3884-1
ISBN (Electronic): 978-1-4799-3885-8
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials
Keywords: fiber amplifier, mode-locked fiber laser, Yb-doped tapered fiber

Bibliographical note

Contribution: organisation=orc,FACT1=1<br/>Portfolio EDEND: 2014-09-30<br/>Publisher name: IEEE

Source: researchoutputwizard
Source ID: 378

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

New multisoliton complex in Bi-doped fiber laser operated at 1450 nm

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Photonics, Research group: Nanophotonics, Ulyanovsk State University, Fiber Optics Research Center of the Russian Academy of Sciences, Russian Academy of Sciences
Contributors: Gumenyuk, R., Rissanen, J., Korobko, D. A., Zolotovskiy, I. O., Melkumov, M., Khopin, V. F.
Publication date: 2017

Host publication information

Title of host publication: European Quantum Electronics Conference 2017
Volume: Part F81-EQEC 2017
Publisher: The Optical Society; OSA
Article number: EF_5_4
ISBN (Electronic): 978-1-5090-6736-7
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Mechanics of Materials
Source: Scopus
Source ID: 85039792281

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Optical properties of GaAs1-xBix/GaAs quantum well structures grown by molecular beam epitaxy on (100) and (311)B GaAs substrates

In this work, the electronic bandstructure of GaAs1-xBix/GaAs single quantum well (QW) samples grown by molecular beam epitaxy is investigated by photomodulated reflectance (PR) measurements as a function of Bi content (0.0065 ≤ x ≤ 0.0215) and substrate orientation. The Bi composition is determined via simulation of high-resolution x-ray diffraction measurement and is found to be maximized in the 2.15%Bi and 2.1%Bi samples grown on (100) and (311)B GaAs substrates. However, the simulations indicate that the Bi composition is not only limited in the GaAsBi QW layer but extends out of the GaAsBi QW towards the GaAs barrier and forms a GaAsBi epilayer. PR spectra are fitted with the third derivative function form (TDFF) to identify the optical transition energies. We analyze the TDFF results by considering strain-induced modification on the conduction band (CB) and splitting of the valence band (VB) due to its interaction with the localized Bi level and VB interaction. The PR measurements confirm the existence of a GaAsBi epilayer via observed optical transitions that belong to GaAsBi layers with various Bi compositions. It is found that both Bi composition and substrate orientation have strong effects on the PR signal. Comparison between TDFF and calculated optical transition energies provides a bandgap reduction of 92 meV/%Bi and 36 meV/%Bi and an interaction strength of the isolated Bi atoms with host GaAs valence band (C BiM ) of 1.7 eV and 0.9 eV for (100) and (311)B GaAs substrates, respectively.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Photonics, Research group: ORC, Adana Science and Technology University, Istanbul University, University of Cukurova, University of Nottingham, Universidade Federal de São Carlos, Leibniz Institute for Crystal Growth
Contributors: Gunes, M., Ukelge, M. O., Donmez, O., Erol, A., Gumus, C., Alghamdi, H., Galeti, H. V., Henini, M., Schmidbauer, M., Hilska, J., Puustinen, J., Guina, M.
Publication date: 13 Nov 2018
Peer-reviewed: Yes

Publication information

Journal: Semiconductor Science and Technology
Volume: 33
Issue number: 12
Article number: 124015
ISSN (Print): 0268-1242
Ratings: 
  • Scopus rating (2018): CiteScore 2.4 SJR 0.744 SNIP 1.014
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Electrical and Electronic Engineering, Materials Chemistry
Keywords: high-index substrate, oriented GaAsBi, photomodulated reflectance, strained quantum well, type I band line-up
Source: Scopus
Source ID: 85057810892

Research output: Contribution to journalArticleScientificpeer-review

Interfacial design and structure of protein/polymer films on oxidized AlGaN surfaces

Protein detection using biologically or immunologically modified field-effect transistors (bio/immunoFETs) depends on the nanoscale structure of the polymer/protein film at sensor interfaces (Bhushan 2010 Springer Handbook of Nanotechnology 3rd edn (Heidelberg: Springer); Gupta et al 2010 The effect of interface modification on bioFET sensitivity, submitted). AlGaN-based HFETs (heterojunction FETs) are attractive platforms for many protein sensing applications due to their electrical stability in high osmolarity aqueous environments and favourable current drive capabilities. However, interfacial polymer/protein films on AlGaN, though critical to HFET protein sensor function, have not yet been fully characterized. These interfacial films are typically comprised of protein-polymer films, in which analyte-specific receptors are tethered to the sensing surface with a heterobifunctional linker molecule (often a silane molecule). Here we provide insight into the structure and tribology of silane interfaces composed of one of two different silane monomers deposited on oxidized AlGaN, and other metal oxide surfaces. We demonstrate distinct morphologies and wear properties for the interfacial films, attributable to the specific chemistries of the silane monomers used in the films. For each specific silane monomer, film morphologies and wear are broadly consistent on multiple oxide surfaces. Differences in interfacial film morphology also drive improvements in sensitivity of the underlying HFET (coincident with, though not necessarily caused by, differences in interfacial film thickness). We present a testable model of the hypothetical differential interfacial depth distribution of protein analytes on FET sensor interfaces with distinct morphologies. Empirical validation of this model may rationalize the actual behaviour of planar immunoFETs, which has been shown to be contrary to expectations of bio/immunoFET behaviour prevalent in the literature for the last 20 years. Improved interfacial properties of bio/immunoHFETs have improved bio/immunoHFET performance: better understanding of interfaces may lead to mechanistic understanding of FET sensor properties and to clinical translation of the immunoFET platform.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Augmented Human Activities (AHA), Ohio State University, Department of Electrical and Computer Engineering
Contributors: Gupta, S. K., Wu, H. H., Kwak, K. J., Casal, P., Nicholson, T. R., Wen, X., Anisha, R., Bhushan, B., Berger, P. R., Lu, W., Brillson, L. J., Lee, S. C.
Publication date: 26 Jan 2011
Peer-reviewed: Yes

Publication information

Journal: Journal of Physics D: Applied Physics
Volume: 44
Issue number: 3
Article number: 34010
ISSN (Print): 0022-3727
Ratings: 
  • Scopus rating (2011): CiteScore 2.36 SJR 1.266 SNIP 1.424
Original language: English
ASJC Scopus subject areas: Condensed Matter Physics, Electronic, Optical and Magnetic Materials, Acoustics and Ultrasonics, Surfaces, Coatings and Films
Source: Scopus
Source ID: 78650639127

Research output: Contribution to journalArticleScientificpeer-review

On the limit of superhydrophobicity: Defining the minimum amount of TiO2 nanoparticle coating

Fabrication of superhydrophobic surfaces in large scale has been in high interest for several years, also titanium oxide nanostructures having been applied for the purpose. Optimizing the amount and structure of the TiO2 material in the coating will play a key role when considering upscaling. Here, we take a look at fabricating the superhydrophobic surface in a one-step roll-to-roll pilot scale process by depositing TiO2 nanoparticles from a Liquid Flame Spray onto a moving paperboard substrate. In order to find the minimum amount of nanomaterial still sufficient for creating superhydrophobicity, we varied nanoparticle production rate, flame distance from the substrate and line speed. Since the deposited amount of material sideways from the flame path was seen to decrease gradually, spatial analysis enabled us to consistently determine the minimum amount of TiO2 nanoparticles on the substrate needed to achieve superhydrophobicity. Amount as low as 20-30 mg m-2 of TiO2 nanoparticles was observed to be sufficient. The scanning electron microscopy revealed that at this amount, the surface was covered with nanoparticles only partially, but still sufficiently to create a hierarchical structure to affect wetting significantly. Based on XPS analysis, it became apparent that TiO2 gathers hydrocarbons on the surface to develop the surface chemistry towards hydrophobic, but below the critical amount of TiO2 nanoparticles, the chemistry could not enable superhydrophobicity anymore. While varying the deposited amount of TiO2, besides the local spatial variance of the coating amount, also the overall yield was studied. Within the text matrix, a yield up to 44% was achieved. In conclusion, superhydrophobicity was achieved at all tested line speeds (50 to 300 m min-1), even if the amount of TiO2 varied significantly (20 to 230 mg m-2).

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Physics, Research group: Aerosol Synthesis, Research area: Aerosol Physics, Materials Science, Packaging Technology Research Team, Physics at Interfaces, Max Planck Institute for Polymer Research, Bioscience and Materials/Surface, RISE Research Institutes of Sweden AB, Finnish Environment Institute, Abo Akad Univ, Abo Akademi University, Dept Phys, AGH University of Science and Technology, University of Eastern Finland
Contributors: Haapanen, J., Aromaa, M., Teisala, H., Juuti, P., Tuominen, M., Sillanpää, M., Stepien, M., Saarinen, J. J., Toivakka, M., Kuusipalo, J., Mäkelä, J. M.
Publication date: 2019
Peer-reviewed: Yes
Early online date: 5 Dec 2018

Publication information

Journal: Materials Research Express
Volume: 6
Issue number: 3
Article number: 035004
ISSN (Print): 2053-1591
Ratings: 
  • Scopus rating (2019): SJR 0.365 SNIP 0.661
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Biomaterials, Surfaces, Coatings and Films, Polymers and Plastics, Metals and Alloys
Keywords: liquid flame spray, nanocoatings, nanoparticles, superhydrophobic, TiO, titanium dioxide, wetting
Source: Scopus
Source ID: 85059238010

Research output: Contribution to journalArticleScientificpeer-review

Graphene-based tunable plasmon induced transparency in gold strips

Plasmon induced transparency (PIT) has been numerically investigated and experimentally realized by two parallel gold strips on graphene for the mid-infrared (MIR) range. The PIT response is realized by the weak hybridization of two bright modes of the gold strips. The response of the device is adjusted with the lengths of two strips and tuned electrically in real time by changing the Fermi level (Ef) of the graphene. Ef is changed to tune the resonance frequency of the transparency window. A top gating is used to achieve high tunability and a 263 nm shift is obtained by changing the gate voltage from -0.6 V to 2.4 V. The spectral contrast ratio of our devices is up to 82%. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Photonics, Bilkent University, Department of Electrical and Electronics Engineering, Laboratory of Photonics
Contributors: Habib, M., Rashed, A. R., Ozbay, E., Caglayan, H.
Number of pages: 6
Pages: 1069-1074
Publication date: 1 Apr 2018
Peer-reviewed: Yes

Publication information

Journal: Optical Materials Express
Volume: 8
Issue number: 4
ISSN (Print): 2159-3930
Ratings: 
  • Scopus rating (2018): CiteScore 2.76 SJR 0.886 SNIP 1.045
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials
Keywords: ELECTROMAGNETICALLY INDUCED TRANSPARENCY, SLOW LIGHT, METAMATERIAL, SPECTROSCOPY, RESONATORS, DYNAMICS, ANALOG
Electronic versions: 
Source: Scopus
Source ID: 85044841180

Research output: Contribution to journalArticleScientificpeer-review

Tunable Reflection Type Plasmon Induced Transparency with Graphene

Plasmon induced transparency (PIT) has always been investigated in transmission mode, which makes the design dependent upon the type of substrate. In this work, we propose a first tunable reflection type PIT (RPIT) device based on simple design of two parallel gold strips on graphene. We have numerically investigated the design by using Finite Difference Time-Domain (FDTD) method. This response is tunable by changing the Fermi level (Ef) of graphene. High tunability of 215 nm shift was observed by changing the Ef of graphene from 0 to 0.8 eV. The spectral contrast ratio of our device is 99.2%.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Photonics, Department of Electrical and Electronics Engineering, Bilkent University, Nanotechnology Research Center
Contributors: Habib, M., Ozbay, E., Caglayan, H.
Number of pages: 3
Pages: 170-172
Publication date: 13 Nov 2018

Host publication information

Title of host publication: 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena, METAMATERIALS 2018
Publisher: IEEE
ISBN (Electronic): 9781538647028
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Acoustics and Ultrasonics, Atomic and Molecular Physics, and Optics, Radiation

Bibliographical note

EXT="Habib, M."

Source: Scopus
Source ID: 85058538366

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Site-controlled InAs Quantum Dots for Plasmonics

We present site-controlled epitaxy of InAs quantum dots (QD) for plasmonics and report QD-plasmon coupling in a hybrid structure consisting of site-controlled InAs/GaAs QD chains in the proximity of an Ag film.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Optoelectronics Research Centre, Research group: Semiconductor Technology and Applications, Research group: Laboratory for Future Electronics, Department of Physics, Research group: Nanophotonics
Contributors: Hakkarainen, T., Tommila, J., Schramm, A., Simonen, J., Niemi, T., Strelow, C., Kipp, T., Kontio, J., Guina, M.
Publication date: 2016

Host publication information

Title of host publication: Conference on Lasers and Electro-Optics 2016 : QELS_Fundamental Science
Publisher: OSA - The Optical Society
Article number: FM1B.3
ISBN (Electronic): 978-1-943580-11-8
ASJC Scopus subject areas: Condensed Matter Physics, Electronic, Optical and Magnetic Materials
Keywords: (250.5403) Plasmonics, (160.4236) Nanomaterials, (160.6000) Semiconductor materials

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Effect of Hole Transporting Material on Charge Transfer Processes in Zinc Phthalocyanine Sensitized ZnO Nanorods

The photoinduced electron transfer processes were studied for hybrid systems consisting of self-assembled monolayer of zinc phthalocyanine (ZnPc) assembled on ZnO nanorods and a film of organic hole transporting material (HTM) atop. Polythiophene (P3HT) or Spiro-OMeTAD were used as HTM. The study was carried out by ultrafast transient absorption spectroscopy technique with selective excitation of ZnPc at 680 nm or P3HT at 500 nm. Data analysis revealed that photoexcitation of ZnPc in the structure ZnO|ZnPc|P3HT results in a fast (1.8 ps) electron transfer from ZnPc to ZnO, which is followed by a hole transfer from the ZnPc cation to P3HT roughly in 30 ps. However, in the case of ZnO|ZnPc|Spiro-OMeTAD structure, the primary reaction upon excitation of ZnPc is a fast (0.5 ps) hole transfer from ZnPc to Spiro-OMeTAD, and the second step is electron injection from the ZnPc anion to ZnO in roughly 120 ps. Thus, we demonstrate two structurally very similar hybrid architectures that implement two different mechanisms for photoinduced charge separation found in dye-sensitized or in organic solar cells.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Chemistry and Bioengineering, Research group: Supramolecular photochemistry
Contributors: Hakola, H., Sariola-Leikas, E., Efimov, A., Tkachenko, N. V.
Number of pages: 8
Pages: 7044-7051
Publication date: 21 Apr 2016
Peer-reviewed: Yes

Publication information

Journal: Journal of Physical Chemistry C
Volume: 120
Issue number: 13
ISSN (Print): 1932-7447
Ratings: 
  • Scopus rating (2016): CiteScore 4.48 SJR 1.964 SNIP 1.189
Original language: English
ASJC Scopus subject areas: Physical and Theoretical Chemistry, Electronic, Optical and Magnetic Materials, Surfaces, Coatings and Films, Energy(all)
Source: Scopus
Source ID: 84964529902

Research output: Contribution to journalArticleScientificpeer-review

Double-asymmetric-structure 1.5 μ m high power laser diodes

Design considerations for high pulsed power and brightness 1.5 μm laser emitters for laser radar applications, based on comprehensive semi-analytical theory, are presented. A strongly asymmetric waveguide design with a bulk active layer positioned very near the p-emitter interface is chosen to minimize the current-induced losses at high power while maintaining a single, broad transverse mode. Moderate to high doping of the n-side of the Optical Confinement Layer and high p-doping of the p-cladding layer are used to reduce the residual current-induced losses and the electric resistance of the structure. For pulsed room-temperature operation, short laser resonators are found to be advantageous. First experimental results are presented. An as-cleaved sample with a stripe width of90 μm and a resonator2 mm long exhibits an output power of about 18 W at a pumping current amplitude of 80 A, with 1 mm long resonators showing higher power output. Further improvements are predicted by structure optimization as well as increase in internal quantum efficiency and thermal performance.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Physics, University of Oulu, Ioffe Physico-Technical Institute, University of York
Contributors: Hallman, L., Ryvkin, B. S., Avrutin, E. A., Aho, A. T., Viheriälä, J., Guina, M., Kostamovaara, J. T.
Number of pages: 2
Pages: 19-20
Publication date: 1 Oct 2019

Host publication information

Title of host publication: Proceedings of the 2019 IEEE High Power Diode Lasers and Systems Conference, HPD 2019 - Co-located with Photonex 2019
Publisher: IEEE
ISBN (Electronic): 9781728130972
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Atomic and Molecular Physics, and Optics
Keywords: efficiency, high power lasers, laser diodes, modelling

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Highly efficient charge separation in model Z-scheme TiO2/TiSi2/Si photoanode by micropatterned titanium silicide interlayer

Atomic layer deposited (ALD) TiO2 is an attractive material for improving the photoactivity and chemical stability of semiconductor electrodes in artificial photosynthesis. Using photoelectrochemical (PEC) measurements, we show that an interfacial, topographically microstructured TiSi2 layer inside the TiO2/Si heterojunction improves the charge carrier separation and shifts the water dissociation onset potential to more negative values. These observations are correlated with the X-ray photoelectron spectroscopy (XPS) and ultra-violet photoelectron spectroscopy (UPS) measurements, which reveal an increased band bending due to the TiSi2 interlayer. Combined with the UV–Vis absorption results, the photoelectron spectroscopy measurements allow the reconstruction of the complete energy band diagram for the TiO2/TiSi2/Si heterojunction and the calculation of the valence and conduction band offsets. The energy band alignment and improvements in PEC results reveal that the charge transfer across the heterojunction follows a Z-scheme model, where the metal-like TiSi2 islands act as recombination centers at the interface.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Research group: Surface Science, Physics
Contributors: Hannula, M., Ali-Löytty, H., Lahtonen, K., Saari, J., Tukiainen, A., Valden, M.
Number of pages: 9
Pages: 237-245
Publication date: 1 Aug 2019
Peer-reviewed: Yes

Publication information

Journal: Acta Materialia
Volume: 174
ISSN (Print): 1359-6454
Ratings: 
  • Scopus rating (2019): SJR 3.662 SNIP 3.037
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Ceramics and Composites, Polymers and Plastics, Metals and Alloys
Keywords: Electrochemical characterization, Electronic band structure, Titanium dioxide, Transition metal silicides, X-ray photoelectron spectroscopy (XPS)
Source: Scopus
Source ID: 85066305210

Research output: Contribution to journalArticleScientificpeer-review

Hot spot temperature in an HTS Coil: Simulations with MIITs and finite element method

MIITs, a zero-dimensional concept to study hot spot temperature, has been previously used to estimate hot spot temperatures and quench heater delays in NbTi and Nb3Sn magnets. However, quench behavior is completely different in high-temperature superconducting (HTS) magnets due to the slow normal zone propagation velocity and the high temperature margin. Because the MIITs concept does not take into account thermal diffusion in the magnet, opposite to the finite-element method (FEM) analysis, the difference of these concepts is studied in this paper. Here, we have taken the approach to compute the hot spot temperatures for a future HTS magnet, designed to be built from REBCO Roebel cable, with MIITs and FEM simulations. The magnet protection is accomplished with a dump resistor, and the effect of quench detection threshold voltage on the hot spot temperature has been studied. Furthermore, the inductance of the magnet increases with the magnet length. Thus, there exists a maximum inductance of the magnet, which should not be exceeded to be able to protect the magnet only with a dump resistor. The hot spot temperatures with different values of inductance are also studied in this paper. Our simulations show that the hot spot temperatures computed with MIITs are from 60 to 150 K higher than those of FEM analysis. Thus, the MIITs concept seems unreliable when considering hot spot temperatures in HTS magnets protected with only dump resistors. However, the MIITs concept might be a usable tool when comparing different magnet designs. If 400 K is the upper limit for the hot spot temperature and the protection scheme includes only a dump resistor, the length of the investigated magnet can be increased to only such value that the magnet inductance is at most 50 mH.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Electrical Engineering, Research area: Electromagnetics, European Organization for Nuclear Research
Contributors: Härö, E., Stenvall, A., Van Nugteren, J., Kirby, G.
Publication date: 1 Apr 2015
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Applied Superconductivity
Volume: 25
Issue number: 2
ISSN (Print): 1051-8223
Ratings: 
  • Scopus rating (2015): CiteScore 1.27 SJR 0.403 SNIP 1.046
Original language: English
ASJC Scopus subject areas: Electrical and Electronic Engineering, Condensed Matter Physics, Electronic, Optical and Magnetic Materials
Keywords: Finite element method (FEM), high-temperature superconductors (HTSs), quench simulation, stability analysis, superconducting magnets
Source: Scopus
Source ID: 84926385685

Research output: Contribution to journalArticleScientificpeer-review

A Novel Enhanced-Performance Flexible RFID-Enabled Embroidered Wireless Integrated Module for Sensing Applications

A novel wireless embroidered integrated platform for radio frequency identification (RFID)-enabled strain sensing that takes advantage of the nonlinear behavior of the RFID chip impedance as a function of the incident power is introduced. Due to the nonlinearity of the chip impedance as a function of the power, a large variation of chip impedance value and thus a large difference of radar cross section values for appropriately chosen power levels are achieved. Taking advantage of this idea, the sensing parameter is detected by interrogation of the sensor tag using two distinct transmitting power levels and calculating the difference of backscattered response. As a proof of concept, we applied the proposed method for the detection of an embroidered RFID-enabled strain sensor that is fabricated using electrotextiles in order to observe the variations of the magnitude and the corresponding strain levels. The proposed model for the chip impedance helps in predicting the RFID chip impedance variation for different strain conditions, an extremely important issue for RF/RFID modules and packages operating over a wide power dynamic range as well as enabling the accurate estimation of the maximum range of the RFID-enabled sensing modules for the maximum allowable power levels.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Sensing Systems for Wireless Medicine (MediSense), Department of Electronics and Communications Engineering, Research group: Wireless Identification and Sensing Systems Research Group, University of Montpellier
Contributors: Hasani, M., Vena, A., Sydänheimo, L., Tentzeris, M. M., Ukkonen, L.
Number of pages: 9
Pages: 1244-1252
Publication date: 2015
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Components, Packaging and Manufacturing Technology
Volume: 5
Issue number: 9
ISSN (Print): 2156-3950
Ratings: 
  • Scopus rating (2015): CiteScore 1.66 SJR 0.499 SNIP 1.156
Original language: English
ASJC Scopus subject areas: Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Industrial and Manufacturing Engineering

Bibliographical note

EXT="Vena, Arnaud"

Research output: Contribution to journalArticleScientificpeer-review

Fabrication and performance evaluation of 3D-printed graphene passive UHF RFID tags on cardboard

This paper discusses the fabrication and wireless performance of 3D-printed graphene-based passive UHF (ultra high frequency) RFID (radiofrequency identification) tags on two different cardboard packaging substrates. Our results confirm that the low-cost and eco-friendly graphene-based RFID tags achieve high performance with attainable read ranges of 3.2-3.8 meters. These results are superior to those of previously reported RFID tags with graphene antennas.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Faculty of Biomedical Sciences and Engineering, Research group: Biomaterials and Tissue Engineering Group, Research group: Wireless Identification and Sensing Systems Research Group, Southeast University
Contributors: He, H., Akbari, M., Chen, X., Nommeots-Nomm, A., Chen, L., Ukkonen, L., Virkki, J.
Number of pages: 4
Pages: 3322-3325
Publication date: 22 May 2017

Host publication information

Title of host publication: 2017 Progress in Electromagnetics Research Symposium - Spring, PIERS 2017
Publisher: IEEE
ISBN (Electronic): 9781509062690
ASJC Scopus subject areas: Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials
Source: Scopus
Source ID: 85044919743

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Power and wavelength scaling using semiconductor disk laser - bismuth fiber MOPA systems

We present a master oscillator power amplifier (MOPA) system that comprises a mode-locked semiconductor disk laser (SDL) emitting at 1.33 mu m and a bismuth-doped fiber amplifier. The mode-locked SDL was fabricated by wafer bonding an InP-based gain section with a GaAs-based distributed Bragg reflector (DBR) using (3-Mercaptopropyl)trimethoxysilane. The bismuth-doped fiber amplifier was pumped with a continuous wave SDL emitting at 1.18 mu m. The MOPA system produced pulses at a repetition rate of 827 MHz with a pulse energy of 0.62 nJ, which corresponds to an average output power of more than 0.5 W.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Frontier Photonics, Optoelectronics Research Centre, Research group: Ultrafast and intense lasers, Research group: Semiconductor Technology and Applications, Ulyanovsk State University, Fiber Optics Research Center, Russian Academy of Sciences
Contributors: Heikkinen, J., Gumenyuk, R., Rantamäki, A., Lyytikäinen, J., Leinonen, T., Zolotovskii, I., Melkumov, M., Dianov, E. M., Okhotnikov, O. G.
Number of pages: 7
Publication date: 2015

Host publication information

Title of host publication: Vertical External Cavity Surface Emitting Lasers (VECSELs) V
Place of publication: BELLINGHAM
Publisher: SPIE
Editor: Guina, M.
Article number: 93490E
ISBN (Print): 9781628414394

Publication series

Name: Proceedings of SPIE
Publisher: SPIE-INT SOC OPTICAL ENGINEERING
Volume: 9349
ISSN (Print): 0277-786X
ASJC Scopus subject areas: Applied Mathematics, Computer Science Applications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Keywords: Semiconductor disk laser (SDL), vertical-external-cavity surface-emitting laser (VECSEL), modelocking, wafer bonding, bismuth-doped fiber, master oscillator power amplifier (MOPA), SUPERCONTINUUM GENERATION, OUTPUT POWER, PICOSECOND, VECSEL, PULSES, GHZ
Source: WOS
Source ID: 000353134900011

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Printable and flexible macroporous organosilica film with high protein adsorption capacity

An approach for creating a flexible and macroporous silsesquioxane film using phase separation method is described. The porous film was prepared by a simple coating method where sol-gel solution containing polyacrylic acid (PAA) and 1,6-bis(trimethoxysilyl)hexane in water was applied on boehmite silica coated polymethylmethacrylate (PMMA) film. After drying, the water soluble PAA template was removed by washing the film with water revealing the porous film. With certain ratios of PAA and water, fully co-continuous pore system with open surface was obtained. Porous films with 3-4 μm thickness were found to be highly flexible. The biocompatibility of the porous film was tested by immobilizing a high affinity biotin-binding chimeric avidin (ChiAVD(I117Y)) into the porous matrix The porous film was found to adsorb higher amounts of functional chimeric avidin compared to the pure PMMA film or a boehmite silica coated PMMA film.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Multi-scaled biodata analysis and modelling (MultiBAM), Univ of Oulu, VTT Technical Research Centre of Finland, School of Management (JKK)
Contributors: Heikkinen, J. J., Kivimäki, L., Hytönen, V. P., Kulomaa, M. S., Hormi, O. E. O.
Number of pages: 4
Pages: 1934-1937
Publication date: 1 Jan 2012
Peer-reviewed: Yes

Publication information

Journal: Thin Solid Films
Volume: 520
Issue number: 6
ISSN (Print): 0040-6090
Ratings: 
  • Scopus rating (2012): CiteScore 1.86 SJR 0.897 SNIP 1.153
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Surfaces and Interfaces, Surfaces, Coatings and Films, Metals and Alloys, Materials Chemistry
Keywords: Flexible coatings, Phase separation, Porous films, Printable coatings, Protein immobilization, Sol-gel
Source: Scopus
Source ID: 84855940396

Research output: Contribution to journalArticleScientificpeer-review

Photocatalytic and antibacterial properties of ZnO films with different surface topographies on stainless steel substrate

Zinc oxide films with three types of topographies: needle-like and hexagonal rods and flakes, were prepared by hydrothermal synthesis on stainless steel substrates to investigate their photocatalytic and antibacterial properties. The photocatalytic activity was measured with a methylene blue (MB) discoloration test, whereas a method using bioluminescent whole cell bacterial biosensors enabling the constant monitoring of the amount of living cells on the surfaces was used here to study the antibacterial properties. The results showed that photocatalytic activity was clearly influenced by the surface area, which is in turn dependent on the topography. Moreover, it was found that all the examined films decreased notably the amount of Staphylococcus aureus and Escherichia coli on the surfaces. Despite significant differences in the surface areas of the studied samples that led to different zinc dissolution rate in aqueous environment, no notable differences in antibacterial activity between the films with different morphologies could be detected. These results are presented and discussed in this paper.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Materials Science, Research group: Ceramic materials, Department of Chemistry and Bioengineering, Research group: Industrial Bioengineering and Applied Organic Chemistry, VTT Technical Research Centre of Finland
Contributors: Heinonen, S., Kannisto, M., Nikkanen, J., Huttunen-Saarivirta, E., Karp, M., Levänen, E.
Number of pages: 8
Pages: 842-849
Publication date: 1 Oct 2016
Peer-reviewed: Yes

Publication information

Journal: Thin Solid Films
Volume: 616
ISSN (Print): 0040-6090
Ratings: 
  • Scopus rating (2016): CiteScore 1.83 SJR 0.639 SNIP 0.863
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Surfaces and Interfaces, Surfaces, Coatings and Films, Metals and Alloys, Materials Chemistry
Keywords: Antibacterial, Biosensor cell, Hydrothermal synthesis, Photocatalytic activity, Zinc oxide
Source: Scopus
Source ID: 84991648557

Research output: Contribution to journalArticleScientificpeer-review

Investigation of long-term chemical stability of structured ZnO films in aqueous solutions of varying conditions

Nanostructured zinc oxide, ZnO, films feature attractive functional properties, but their long-term stability needs further investigation. Here, ZnO thin films with well-aligned rod-like structure were grown on stainless steel substrate. The long-term chemical stability of the ZnO films was investigated in solutions with varying pH values (3 − 11) to enhance knowledge about the durability of films in acidic and basic environments. The solubility and stability of the films in the solutions were investigated using atomic absorption spectrophotometry, scanning electron microscopy imaging and energy-dispersive X-ray spectroscopy analyses, as well as by monitoring changes in water contact angle of the films and in the pH values of the solutions. The ZnO film was found to be most stable at highest pH value, with the amount of dissolved zinc being lowest among the studied pH values and the changes observed with other characterization methods being minor compared to the samples immersed to other solutions. At the lowest pH, the film was removed rapidly from the substrate by dissolution. In solutions featuring pH values 5 and 9, the measured pH was unstable and changed constantly until it reached the value 7.2–7.6, i.e., until the equilibrium of different chemical species in the solution was achieved. These results are presented and discussed in this paper from the viewpoint of applicability of the ZnO films.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Materials Science, Research group: Ceramic materials, VTT Technical Research Centre of Finland
Contributors: Heinonen, S., Nikkanen, J., Huttunen-Saarivirta, E., Levänen, E.
Number of pages: 10
Pages: 410-419
Publication date: 30 Sep 2017
Peer-reviewed: Yes

Publication information

Journal: Thin Solid Films
Volume: 638
ISSN (Print): 0040-6090
Ratings: 
  • Scopus rating (2017): CiteScore 1.91 SJR 0.617 SNIP 0.864
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Surfaces and Interfaces, Surfaces, Coatings and Films, Metals and Alloys, Materials Chemistry
Keywords: Chemical stability, Hydrothermal synthesis, pH, Solubility, Thin film, Zinc oxide
Source: Scopus
Source ID: 85027885831

Research output: Contribution to journalArticleScientificpeer-review

Aryl end-capped quaterthiophenes applied as anode interfacial layers in inverted organic solar cells

Four aryl end-capped quaterthiophene derivatives were synthesized and their material properties were studied by computational, spectroscopic, electrochemical, and thermoanalytical methods. Compounds were applied as interfacial layers between the bulk heterojunction active layer and Ag anode in inverted organic solar cells. Results show that p-cyanophenyl end-capped quaterthiophene with hexyl side chains increases both the short circuit current density and power conversion efficiency notably compared to reference interlayer material, tris-(8-hydroxyquinoline)aluminum. The improved cell performance was attributed to the optimal positions of the highest occupied molecular orbital and the lowest unoccupied molecular orbital (LUMO) of this material, relative to those of the photoactive electron donor poly(3-hexylthiophene) and Ag anode, and evenly distributed LUMO. In addition, the use of these materials as an anode interfacial layer increases the absorption of the solar cell, which could contribute to the formation of excitons and additional current production by the cell.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Chemistry and Bioengineering, Research group: Supramolecular photochemistry, Frontier Photonics, University of Oulu, Department of Chemistry and Mathematics, Faculty of Petroleum and Mining Engineering, Suez University
Contributors: Heiskanen, J. P., Manninen, V. M., Pankov, D., Omar, W. A. E., Kastinen, T., Hukka, T. I., Lemmetyinen, H. J., Hormi, O. E. O.
Number of pages: 11
Pages: 196-206
Publication date: 1 Jan 2015
Peer-reviewed: Yes

Publication information

Journal: Thin Solid Films
Volume: 574
ISSN (Print): 0040-6090
Ratings: 
  • Scopus rating (2015): CiteScore 1.84 SJR 0.68 SNIP 0.923
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Materials Chemistry, Metals and Alloys, Surfaces, Coatings and Films, Surfaces and Interfaces
Keywords: Anode interfacial layer, Bulk heterojunction, Computational research, Inverted organic solar cell, Oligothiophene, Spectroscopy, Suzuki-Miyaura

Bibliographical note

EXT="Heiskanen, J. P."

Source: Scopus
Source ID: 84921286591

Research output: Contribution to journalArticleScientificpeer-review

Teaching for virtual work

Universities are still mainly preparing students for the world, where 'do something useful', i.e. 'do something with your hands' was the main principle and work was done during strictly regulated time. But world has changed and traditional areas of human activity (what also are the main target in University courses) are rapidly diminishing. More important have become virtual products - computer programs, mobile apps, social networks, new types of digital currencies, IOT (voice in your bathroom suggesting to buy the next model of Alexa), video games, interactive TV, virtual reality etc. Most of these new areas are not present in current curricula and there are problems with involving them in curricula - (working) students know (some aspects of) these areas better than many of university teachers, since corresponding knowledge is not yet present in textbooks - it is present only on Internet. The Internet strongly influences both what we teach and how we teach.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Computing Sciences, Tallinn University of Technology, University of Lapland
Contributors: Henno, J., Jaakkola, H., Mäkelä, J.
Number of pages: 9
Pages: 818-826
Publication date: 1 May 2019

Host publication information

Title of host publication: 2019 42nd International Convention on Information and Communication Technology, Electronics and Microelectronics, MIPRO 2019 - Proceedings
Publisher: IEEE
Editors: Skala, K., Car, Z., Pale, P., Huljenic, D., Janjic, M., Koricic, M., Sruk, V., Ribaric, S., Grbac, T. G., Butkovic, Z., Cicin-Sain, M., Skvorc, D., Mauher, M., Babic, S., Gros, S., Vrdoljak, B., Tijan, E.
ISBN (Electronic): 9789532330984
ASJC Scopus subject areas: Computer Networks and Communications, Hardware and Architecture, Information Systems, Energy Engineering and Power Technology, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Wetting hysteresis induced by temperature changes: Supercooled water on hydrophobic surfaces

The state and stability of supercooled water on (super)hydrophobic surfaces is crucial for low temperature applications and it will affect anti-icing and de-icing properties. Surface characteristics such as topography and chemistry are expected to affect wetting hysteresis during temperature cycling experiments, and also the freezing delay of supercooled water. We utilized stochastically rough wood surfaces that were further modified to render them hydrophobic or superhydrophobic. Liquid flame spraying (LFS) was utilized to create a multi-scale roughness by depositing titanium dioxide nanoparticles. The coating was subsequently made non-polar by applying a thin plasma polymer layer. As flat reference samples modified silica surfaces with similar chemistries were utilized. With these substrates we test the hypothesis that superhydrophobic surfaces also should retard ice formation. Wetting hysteresis was evaluated using contact angle measurements during a freeze-thaw cycle from room temperature to freezing occurrence at -7 °C, and then back to room temperature. Further, the delay in freezing of supercooled water droplets was studied at temperatures of -4 °C and -7 °C. The hysteresis in contact angle observed during a cooling-heating cycle is found to be small on flat hydrophobic surfaces. However, significant changes in contact angles during a cooling-heating cycle are observed on the rough surfaces, with a higher contact angle observed on cooling compared to during the subsequent heating. Condensation and subsequent frost formation at sub-zero temperatures induce the hysteresis. The freezing delay data show that the flat surface is more efficient in enhancing the freezing delay than the rougher surfaces, which can be rationalized considering heterogeneous nucleation theory. Thus, our data suggests that molecular flat surfaces, rather than rough superhydrophobic surfaces, are beneficial for retarding ice formation under conditions that allow condensation and frost formation to occur.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Physics, Research area: Aerosol Physics, Research group: Aerosol Synthesis, KTH Royal Institute of Technology, Surface and Corrosion Science, SP Technical Research Institute of Sweden, Department of Civil and Architectural Engineering, Nanostructure Physics
Contributors: Heydari, G., Sedighi Moghaddam, M., Tuominen, M., Fielden, M., Haapanen, J., Mäkelä, J. M., Claesson, P. M.
Number of pages: 13
Pages: 21-33
Publication date: 15 Apr 2016
Peer-reviewed: Yes

Publication information

Journal: Journal of Colloid and Interface Science
Volume: 468
ISSN (Print): 0021-9797
Ratings: 
  • Scopus rating (2016): CiteScore 4.14 SJR 1.156 SNIP 1.277
Original language: English
ASJC Scopus subject areas: Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, Biomaterials, Colloid and Surface Chemistry
Keywords: Contact angle, Hydrophobization, Liquid flame spray (LFS), Morphology, Multi-scale roughness, Plasma polymerization, Supercooled water, Superhydrophobicity, Wetting hysteresis, Wood
Source: Scopus
Source ID: 84955276633

Research output: Contribution to journalArticleScientificpeer-review

Transparent Yb3+ doped phosphate glass-ceramics

Yb3+ doped oxyfluorophosphate glasses with the composition (98.75) [90NaPO3-(10-x) Na2O-xNaF] - 1.25Yb2O3 (in mol%) with x = 0, 2.5, 5, 7.5 and 10 were prepared using a standard melting process. The progressive replacement of Na2O by NaF leads to an increase in the number of Q2 units at the expense of the Q1 units. This increase in the polymerization of the glass network leads to a shift of the optical band gap to lower wavelength, to a slight increase in the intensity of the emission at 1000 nm and more importantly to a change in the glass crystallization process. Indeed, both surface and bulk crystallization were observed in the glass with x = 0 while surface crystallization only occurs when NaF is added in the phosphate network. The heat treatment leads to the precipitation of at least three crystalline phases: as x increases, the NaPO3 phase grows at the expense of Na5P3O10. All glasses precipitate the Yb containing crystal, NaYbP2O7 which leads to an increase in the intensity of the emission at 1000 nm compared to the emission at 975 nm. We show for the first time to the best of our knowledge that transparent Yb3+ doped phosphate glass-ceramics can be obtained within this glass system when free of NaF.

General information

Publication status: E-pub ahead of print
MoE publication type: A1 Journal article-refereed
Organisations: Physics, Fondazione LINKS – Leading Innovation & Knowledge for Society, CNRS, Université de Bordeaux, ICMCB
Contributors: Hongisto, M., Veber, A., Boetti, N. G., Danto, S., Jubera, V., Petit, L.
Publication date: 1 Jan 2020
Peer-reviewed: Yes

Publication information

Journal: Ceramics International
ISSN (Print): 0272-8842
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Ceramics and Composites, Process Chemistry and Technology, Surfaces, Coatings and Films, Materials Chemistry
Keywords: Glass-ceramic, Luminescence, Phosphate glass, XRD, Yb
Source: Scopus
Source ID: 85077933290

Research output: Contribution to journalArticleScientificpeer-review

Special Issue: Mid-infrared optical materials and their device applications

The mid-infrared (mid-IR, 2 to 10 μm) is a technologically important spectral regime for sensing, imaging, and communications. In the past few years, there has been a surge of interest in novel mid-IR optical materials as well as their device implementations to address the increasing demands from these applications. The 22 papers in this feature issue represent a diverse cross-section of the latest technological advances in this field, spanning mid-IR light generation, propagation, manipulation, and detection functions in free-space, fiber, and planar platforms. In terms of material systems, semiconductors, glasses, plasmonic metals, as well as nanostructures specifically engineered for the mid-IR band, are all extensively covered. We hope that the readers will enjoy the kaleidoscopic view of the burgeoning field of mid-IR optics and photonics through this feature issue.

General information

Publication status: Published
MoE publication type: C2 Edited books
Organisations: Physics, Research group: Photonics Glasses, Massachusetts Institute of Technology, University of Wisconsin-Madison, The Aerospace Corporation, Jet Propulsion Laboratory, California Institute of Technology
Contributors: Hu, J. (ed.), Mawst, L. (ed.), Moss, S. (ed.), Petit, L. (ed.), Ting, D. (ed.)
Publication date: 2018
Peer-reviewed: Yes

Publication information

Journal: Optical Materials Express
Volume: 8
Issue number: 7
ISSN (Print): 2159-3930
Ratings: 
  • Scopus rating (2018): CiteScore 2.76 SJR 0.886 SNIP 1.045
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials
Source: Scopus
Source ID: 85070797189

Research output: Contribution to journalSpecial issueScientificpeer-review

Tuneable topological domain wall states in engineered atomic chains

Topological modes in one- and two-dimensional systems have been proposed for numerous applications utilizing their exotic electronic responses. The 1D, zero-energy, topologically protected end modes can be realized in structures implementing the Su–Schrieffer–Heeger (SSH) model. While the edge modes in the SSH model are at exactly the mid-gap energy, other paradigmatic 1D models such as trimer and coupled dimer chains have non-zero energy boundary states. However, these structures have not been realized in an atomically tuneable system that would allow explicit control of the edge modes. Here, we demonstrate atomically controlled trimer and coupled dimer chains realized using chlorine vacancies in the c(2 × 2) adsorption layer on Cu(100). This system allows wide tuneability of the domain wall modes that we experimentally demonstrate using low-temperature scanning tunneling microscopy (STM).

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Physics, Research area: Computational Physics, Aalto University, Helsinki Institute of Physics, Max-Planck-Institut für Festkörperforschung
Contributors: Huda, M. N., Kezilebieke, S., Ojanen, T., Drost, R., Liljeroth, P.
Number of pages: 5
Publication date: 2020
Peer-reviewed: Yes

Publication information

Journal: npj Quantum Materials
Volume: 5
Issue number: 1
Article number: 17
ISSN (Print): 2397-4648
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Source: Scopus
Source ID: 85081728975

Research output: Contribution to journalArticleScientificpeer-review

Dissolution behavior of the bioactive glass S53P4 when sodium is replaced by potassium, and calcium with magnesium or strontium

The initial dissolution behavior of glasses based on bioactive glass S53P4 was studied with a dynamic measurement setup in a Tris-buffered solution. The glass composition was modified systematically on a molar basis by replacing sodium oxide with potassium oxide (0-100% K) and calcium oxide with magnesium (0-18% Mg) or strontium oxide (0-100% Sr). The concentrations of the ions dissolving from the glasses were measured continuously on-line in the fluid flow for 15 to 25 min using an inductively coupled plasma emission optical spectrometer. This method enabled attainment of detailed information on the initial dissolution mechanisms without the, for bioactive glasses typical, interference of apatite layer formation. The results showed that initial dissolutions of sodium and potassium were markedly higher from the mixed alkali oxide glasses than from the compositions containing only one alkali oxide. Introducing MgO in S53P4 caused a minor decrease in the dissolution rates of all ions. The glass containing 3 mol% of MgO showed the best chemical durability. In contrast, replacing CaO gradually with SrO increased the dissolution rates of all ions. The glasses with the highest replacement of CaO with SrO showed rapid release of both Sr and Na ions. The results corroborate the overall knowledge of glass durability and can be utilized to design bioactive glasses with controlled ion release rate for tissue engineering applications.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Electronics and Communications Engineering, Research group: Biomaterials and Tissue Engineering Group, Johan Gadolin Process Chemistry Centre, Abo Akademi University, Paroc Group Oy, Åbo Akademi University
Contributors: Hupa, L., Fagerlund, S., Massera, J., Björkvik, L.
Number of pages: 6
Pages: 41-46
Publication date: 2016
Peer-reviewed: Yes
Early online date: 10 Apr 2015

Publication information

Journal: Journal of Non-Crystalline Solids
ISSN (Print): 0022-3093
Ratings: 
  • Scopus rating (2016): CiteScore 2.02 SJR 0.685 SNIP 1.154
Original language: English
ASJC Scopus subject areas: Condensed Matter Physics, Ceramics and Composites, Electronic, Optical and Magnetic Materials, Materials Chemistry
Keywords: Bioactive glass, Chemical durability, Dynamic solution, Ion dissolution
Source: Scopus
Source ID: 84948073019

Research output: Contribution to journalArticleScientificpeer-review

Multistep Bloch-line-mediated Walker breakdown in ferromagnetic strips

A well-known feature of magnetic field driven dynamics of domain walls in ferromagnets is the existence of a threshold driving force at which the internal magnetization of the domain wall starts to precess - a phenomenon known as the Walker breakdown - resulting in an abrupt drop of the domain-wall propagation velocity. Here, we report on micromagnetic simulations of magnetic field driven domain-wall dynamics in thin ferromagnetic strips with perpendicular magnetic anisotropy which demonstrate that in wide enough strips Walker breakdown is a multistep process: It consists of several distinct velocity drops separated by short linear parts of the velocity vs field curve. These features originate from the repeated nucleation, propagation, and annihilation of an increasing number of Bloch lines within the domain wall as the driving field magnitude is increased. This mechanism arises due to magnetostatic effects breaking the symmetry between the two ends of the domain wall.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Physics, Aalto University, COMP Centre of Excellence, Computational Physics Laboratory
Contributors: Hütner, J., Herranen, T., Laurson, L.
Publication date: 24 May 2019
Peer-reviewed: Yes

Publication information

Journal: Physical Review B
Volume: 99
Issue number: 17
Article number: 174427
ISSN (Print): 2469-9950
Ratings: 
  • Scopus rating (2019): SJR 1.811 SNIP 1.025
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Source: Scopus
Source ID: 85066395811

Research output: Contribution to journalArticleScientificpeer-review

Nonlinear optical activity effects in complex anisotropic three-dimensional media

We perform numerical modelling of nonlinear optical (NLO) microscopy of complex anisotropic three-dimensional (3D) media using the uncoupled dipole approximation. The modelling is applied to 3D biological microstructures resembling collagen fibers and multilamellar vesicles. The results elucidate how nonlinear optical activity effects, such as secondharmonic generation circular dichroism, can arise from 3D morphological chirality, in addition to molecular level chirality. We also show how thirdharmonic generation circular dichroism could act as a contrast mechanism for visualizing local structural ordering in 3D anisotropic materials.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Physics, Tampere University of Technology, Research area: Optics, Research group: Nonlinear Optics, Frontier Photonics, Aalto University, National Taiwan University, Molecular Imaging Center, COMP Centre of Excellence, Department of Applied Physics, Aalto University
Contributors: Huttunen, M. J., Partanen, M., Bautista, G., Chu, S., Kauranen, M.
Number of pages: 11
Pages: 11-21
Publication date: 2015
Peer-reviewed: Yes

Publication information

Journal: Optical Materials Express
Volume: 5
Issue number: 1
ISSN (Print): 2159-3930
Ratings: 
  • Scopus rating (2015): CiteScore 3.07 SJR 1.34 SNIP 1.335
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials
Source: Scopus
Source ID: 84920996741

Research output: Contribution to journalArticleScientificpeer-review

Investigating human skin using deep learning enhanced multiphoton microscopy

Histopathological image analysis of stained tissue slides is routinely performed by a pathologist to diagnose diseases, such as cancers. Although the approach is effective, it is labor-intensive, time-consuming and risks being biased. Therefore, it would be beneficial to develop faster and more cost-effective approaches. Multiphoton microscopy can alleviate these problems by allowing label-free imaging with high contrast. When label-free multiphoton microscopy is combined with deep learning based image analysis, a wide variety of possibilities arise for the real-time characterization and diagnosis of tissues. Here, we overview our recent work on this topic focusing on automated classification of tissue images taken from human skin near the dermoepidermal junction.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Physics, Research group: Nonlinear Optics, University Politehnica of Bucharest, Carol Davila University of Medicine and Pharmacy
Contributors: Huttunen, M. J., Hristu, R., Dumitru, A., Costache, M., Stanciu, S. G.
Publication date: 1 Jul 2019

Host publication information

Title of host publication: 21st International Conference on Transparent Optical Networks, ICTON 2019
Publisher: IEEE
ISBN (Electronic): 9781728127798

Publication series

Name: International Conference on Transparent Optical Networks
ISSN (Electronic): 2161-2064
ASJC Scopus subject areas: Computer Networks and Communications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials
Keywords: Deep learning, Label-free, Machine learning, Nonlinear microscopy, Tissue characterization

Bibliographical note

jufoid=72297

Source: Scopus
Source ID: 85073067873

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Towards efficient nonlinear plasmonic metasurfaces

Nonlinear processes are important in many fields of photonics ranging from biomedical imaging to ultrashort pulse generation. Progress in nanophotonics and metamaterials has created a growing demand for nanoscale nonlinear optical components. However, it is difficult to answer this demand by using traditional materials motivating the search for alternatives approaches. Nonlinear plasmonics has emerged as a viable solution for enabling efficient and nanoscale nonlinear optics. Despite steady progress, so far achieved conversion efficiencies of metamaterials have not yet rivalled conventional nonlinear materials. Here, we discuss our recent progress in development of efficient nonlinear plasmonic metamaterials. Focus is on metasurfaces utilizing collective responses known as surface lattice resonances, which can be used to dramatically boost nonlinear responses of metasurfaces.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Physics, Research group: Nonlinear Optics, Tampere University, University of Ottawa, Canada, Institute of Physics, Nicolaus Copernicus University, University of Eastern Finland, CRPP, University of Rochester
Contributors: Huttunen, M. J., Stolt, T., Reshef, O., Kiviniemi, A., Czaplicki, R., Zang, X., Vartiainen, I., Butet, J., Kuittinen, M., Martin, O. J., Dolgaleva, K., Boyd, R. W., Kauranen, M.
Publication date: 1 Jul 2019

Host publication information

Title of host publication: 21st International Conference on Transparent Optical Networks, ICTON 2019
Publisher: IEEE
ISBN (Electronic): 9781728127798

Publication series

Name: International Conference on Transparent Optical Networks
ISSN (Electronic): 2161-2064
ASJC Scopus subject areas: Computer Networks and Communications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials
Keywords: Frequency conversion, Metasurfaces, Nonlinear metamaterials, Surface lattice resonances

Bibliographical note

jufoid=72297
EXT="Czaplicki, Robert"
INT=phys,"Stolt, Timo"

Source: Scopus
Source ID: 85073076777

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Third order nonlinear optical response of TTF-based molecular corners

Comparative study of the nonlinear optical response of pyrrolo- tetrathiafulvalene polygons has been carried out. These materials are of great importance for photonics, because they can be used as building blocks for more complicated molecular systems like rotaxanes, catenanes which are promising candidates for opto-electronic applications like optical computing, optical switching etc. During this work the third order nonlinear susceptibility (X (3)) has been determined by the Degenerate Four Wave Mixing experiment, while the imaginary part of the X (3), which is related with the nonlinear absorption was determined by "open-aperture" Z-scan measurements. Moreover measurements have been carried out in order to provide information about the optical limiting efficiency of the materials. High X (3) has been found reaching 2.30 × 10 -21 m 2/V 2, corresponding to second order hyperpolarizability γ values of about 6.5 × 10 -45 m 5/V 2.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Frontier Photonics, CNRS, Centre National de la Recherche Scientifique (CNRS), Universite de Bordeaux - PRES, Lab Bordelais Rech Informat, PICTURA Res Grp, UMR 5800, Univ Angers, Centre National de la Recherche Scientifique (CNRS), University of Nantes Angers Le Mans, University of Angers, CNRS UMR 6200, Inst Sci & Technol Mol Angers, LUNAM Université, Laboratoire MOLTECH-Anjou
Contributors: Iliopoulos, K., Czaplicki, R., Ouazzani, H. E., Balandier, J., Chas, M., Goeb, S., Sallé, M., Gindre, D., Sahraoui, B.
Number of pages: 8
Pages: 205-212
Publication date: 2012
Peer-reviewed: Yes

Publication information

Journal: Nonlinear Optics, Quantum Optics
Volume: 43
Issue number: 1-4
ISSN (Print): 1543-0537
Ratings: 
  • Scopus rating (2012): CiteScore 0.45 SJR 0.211 SNIP 0.272
Original language: English
ASJC Scopus subject areas: Atomic and Molecular Physics, and Optics, Statistical and Nonlinear Physics, Instrumentation, Computer Science(all), Electronic, Optical and Magnetic Materials
Keywords: Degenerate four wave mixing (DFWM), Nonlinear optical response, TTF derivatives, Z-scan
Source: Scopus
Source ID: 84862149419

Research output: Contribution to journalArticleScientificpeer-review

Photovoltaic properties of low-bandgap (0.7–0.9 eV) lattice-matched GaInNAsSb solar junctions grown by molecular beam epitaxy on GaAs

We demonstrate single junction GaInNAsSb solar cells with high nitrogen content, i.e. in the range of 5–8%, and bandgap energies close to 0.7 eV grown by molecular beam epitaxy. A good crystalline quality is demonstrated for the entire range of N concentrations. An average external quantum efficiency of 0.45 is demonstrated for GaInNAsSb solar cell with 6.2% N exhibiting a bandgap of 0.78 eV (no antireflection coatings has been applied). The internal quantum efficiency for the cell is 0.65 at E g + 0.2 eV. The solar cells exhibited bandgap-voltage offsets between 0.55 V (for N = 5.3%) and 0.66 V (for N = 7.9%). When used in a six-junction solar cell architecture under AM1.5D illumination, the estimated short-circuit current density corresponding to the 0.78 eV cell is 8.2 mA/cm 2 . Furthermore, using the parameters obtained for the GaInNAsSb junction with 6.2% N, we have estimated that such six-junction solar cell architecture could realistically attain an efficiency of over 50% at 1000 suns concentration.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Physics, Research group: ORC, Research group: Nanophotonics, Microscopy Center
Contributors: Isoaho, R., Aho, A., Tukiainen, A., Aho, T., Raappana, M., Salminen, T., Reuna, J., Guina, M.
Number of pages: 6
Pages: 198-203
Publication date: 15 Jun 2019
Peer-reviewed: Yes

Publication information

Journal: Solar Energy Materials and Solar Cells
Volume: 195
ISSN (Print): 0927-0248
Ratings: 
  • Scopus rating (2019): SJR 1.827 SNIP 1.799
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Renewable Energy, Sustainability and the Environment, Surfaces, Coatings and Films
Keywords: Dilute nitrides, GaInNAsSb, Molecular beam epitaxy, Multijunction solar cells
Source: Scopus
Source ID: 85062810786

Research output: Contribution to journalArticleScientificpeer-review

Narrow Bandgap Dilute Nitride Materials for 6-junction Space Solar Cells

Narrow bandgap p-i-n dilute nitride GaInNAsSb junctions, for use as bottom cell in 6-junction solar cells, are reported. In particular, we demonstrate a high optical quality for GaInNAsSb junction with a bandgap ~0.78 eV, corresponding to a N content of 6.2%. Under AM0 illumination, such cell exhibits a photocurrent of 36.6 mA/cm2. By extracting the parameters of the experimental cell, we estimate the the AM0 efficiency of a 6-junction multijunction solar cell employing the GaInNAsSb junction, to attain a value of 33%. Further improvements are discussed towards achieving the full potential of the 6-junction design.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Physics, Research group: ORC, Research group: Nanophotonics
Contributors: Isoaho, R., Aho, A., Tukiainen, A., Aho, T., Raappana, M., Salminen, T., Reuna, J., Guina, M.
Number of pages: 3
Publication date: 2019

Host publication information

Title of host publication: 2019 European Space Power Conference (ESPC)
Publisher: IEEE
ISBN (Print): 978-1-7281-2127-7
ISBN (Electronic): 978-1-7281-2126-0
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Renewable Energy, Sustainability and the Environment
Keywords: Solar cell, dilute nitride semiconductors, III-V semiconductor

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Measuring optical anisotropy in poly(3,4-ethylene dioxythiophene): poly(styrene sulfonate) films with added graphene

Abstract Graphene is a 2D nanomaterial having a great potential for applications in electronics and optoelectronics. Composites of graphene with conducting polymers have shown high performance in practical devices and their solution-processability enables low-cost and high-throughput mass manufacturing using printing techniques. Here we measure the effect of incorporation of graphene into poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) to the optical anisotropy, absorbance and conductivity of the film. Uniaxial anisotropy in PEDOT:PSS films has been thought to be caused by the spin-coating process used in fabrication. We have characterized spray- and spin-coated films using ellipsometry and total internal reflection spectroscopy, the latter especially for films too thick and uneven for ellipsometry, and show that spray-coating, similar to inkjet printing, also produces consistently anisotropic properties even in very thick and uneven films. Possible plasmonic excitations related to graphene are not seen in the films. The optical and electrical anisotropy of graphene/PEDOT:PSS enables routes to high performance devices for electronics, photonics and optoelectronics.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Automation Science and Engineering, Research area: Microsystems, Research area: Measurement Technology and Process Control, Integrated Technologies for Tissue Engineering Research (ITTE), Miktech Oy, University of Jyväskylä
Contributors: Isoniemi, T., Tuukkanen, S., Cameron, D. C., Simonen, J., Toppari, J. J.
Number of pages: 7
Pages: 317-323
Publication date: 9 Jul 2015
Peer-reviewed: Yes

Publication information

Journal: Organic Electronics
Volume: 25
ISSN (Print): 1566-1199
Ratings: 
  • Scopus rating (2015): CiteScore 3.6 SJR 1.135 SNIP 1.071
Original language: English
ASJC Scopus subject areas: Biomaterials, Electronic, Optical and Magnetic Materials, Materials Chemistry, Electrical and Electronic Engineering, Chemistry(all), Condensed Matter Physics
Keywords: PEDOT: PSS, Graphene, Anisotropy, Spectroscopy, Conducting polymer, CARBON-NANOTUBE, ELECTRONICS, OPTOELECTRONICS, CONDUCTIVITY, TRANSPARENT, PHOTONICS, GROWTH, CELLS

Bibliographical note

Versio ja lupa ok 13.1.2016 /KK
EXT="Simonen, Janne"

Source: Scopus
Source ID: 84936759109

Research output: Contribution to journalArticleScientificpeer-review

Dots-on-the-fly electron beam lithography

We demonstrate a novel approach for electron-beam lithography (EBL) of periodic nanostructures. This technique can rapidly produce arrays of various metallic and etched nanostructures with line and pitch dimensions approaching the beam spot size. Our approach is based on often neglected functionality which is inherent in most modern EBL systems. The raster/vector beam exposure system of the EBL software is exploited to produce arrays of pixel-like spots without the need to define coordinates for each spot in the array. Producing large arrays with traditional EBL techniques is cumbersome during pattern design, usually leads to large data files and easily results in system memory overload during patterning. In Dots-on-The-fly (DOTF) patterning, instead of specifying the locations of individual spots, a boundary for the array is given and the spacing between spots within the boundary is specified by the beam step size. A designed pattern element thus becomes a container object, with beam spacing acting as a parameterized location list for an array of spots confined by that container. With the DOTF method, a single pattern element, such as a square, rectangle or circle, can be used to produce a large array containing thousands of spots. In addition to simple arrays of nano-dots, we expand the technique to produce more complex, highly tunable arrays and structures on substrates of silicon, ITO/ FTO coated glass, as well as uncoated fused silica, quartz and sapphire.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Department of Electronics and Communications Engineering, Research group: Wireless Communications and Positioning, Optoelectronics Research Centre, Research group: Nanophotonics
Contributors: Isotalo, T. J., Niemi, T.
Number of pages: 7
Publication date: 2016

Host publication information

Title of host publication: SPIE Proceedings : Alternative Lithographic Technologies VIII
Volume: 9777
Publisher: SPIE
Editor: Bencher, C.
Article number: 97771E
ISBN (Electronic): 9781510600126

Publication series

Name: Proceedings of SPIE
Publisher: SPIE
ISSN (Print): 0277-786X
ISSN (Electronic): 1996-756X
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Computer Science Applications, Electrical and Electronic Engineering, Applied Mathematics
Keywords: electron beam lithography, nano-fabrication, nano-particle arrays, optoelectronics, periodic nano-structures, plasmonics
Source: Scopus
Source ID: 84981516864

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Vortex stabilization by means of spatial solitons in nonlocal media

We investigate how optical vortices, which tend to be azimuthally unstable in local nonlinear materials, can be stabilized by a copropagating coaxial spatial solitary wave in nonlocal, nonlinear media. We focus on the formation of nonlinear vortex-soliton vector beams in reorientational soft matter, namely nematic liquid crystals, and report on experimental results, as well as numerical simulations.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Physics
Contributors: Izdebskaya, Y., Krolikowski, W., Smyth, N. F., Assanto, G.
Publication date: 1 May 2016
Peer-reviewed: Yes

Publication information

Journal: Journal of Optics
Volume: 18
Issue number: 5
Article number: 054006
ISSN (Print): 2040-8978
Ratings: 
  • Scopus rating (2016): CiteScore 1.63 SJR 0.715 SNIP 0.829
Original language: English
ASJC Scopus subject areas: Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials
Keywords: liquid crystals, optical vortex, self-action effects, spatial solitons
Source: Scopus
Source ID: 84969245814

Research output: Contribution to journalArticleScientificpeer-review

Artificial intelligence yesterday, today and tomorrow

Artificial Intelligence (AI) is one of the current emerging technologies. In the history of computing AI has been in the similar role earlier - almost every decade since the 1950s, when the programming language Lisp was invented and used to implement self-modifying applications. The second time that AI was described as one of the frontier technologies was in the 1970s, when Expert Systems (ES) were developed. A decade later AI was again at the forefront when the Japanese government initiated its research and development effort to develop an AI-based computer architecture called the Fifth Generation Computer System (FGCS). Currently in the 2010s, AI is again on the frontier in the form of (self-)learning systems manifesting in robot applications, smart hubs, intelligent data analytics, etc. What is the reason for the cyclic reincarnation of AI? This paper gives a brief description of the history of AI and also answers the question above. The current AI “cycle” has the capability to change the world in many ways. In the context of the CE conference, it is important to understand the changes it will cause in education, the skills expected in different professions, and in society at large.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Computing Sciences, Tallinn University of Technology, University of Lapland, Computer Science Institute
Contributors: Jaakkola, H., Henno, J., Mäkelä, J., Thalheim, B.
Number of pages: 8
Pages: 860-867
Publication date: 1 May 2019

Host publication information

Title of host publication: 2019 42nd International Convention on Information and Communication Technology, Electronics and Microelectronics, MIPRO 2019 - Proceedings
Publisher: IEEE
Editors: Skala, K., Car, Z., Pale, P., Huljenic, D., Janjic, M., Koricic, M., Sruk, V., Ribaric, S., Grbac, T. G., Butkovic, Z., Cicin-Sain, M., Skvorc, D., Mauher, M., Babic, S., Gros, S., Vrdoljak, B., Tijan, E.
ISBN (Electronic): 9789532330984
ASJC Scopus subject areas: Computer Networks and Communications, Hardware and Architecture, Information Systems, Energy Engineering and Power Technology, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials
Keywords: Artificial Intelligence, Computer, Computer-supported decision-making, Deep learning, Education, Emerging technology, Expert Systems, Fifth Generation Computer, Frontier technology, Learning, Lisp, Prolog

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Design, fabrication, and testing of a low AC-loss conduction-cooled cryostat for magnetization loss measurement apparatus

Conduction cooling has become a viable alternative for cooling superconducting devices. However, the thermal pathways of a conduction-cooled cryostat can be problematic for applications where time-varying magnetic fields are present. Such alternating magnetic fields are present, e.g., in a magnetization ac-loss measurement system. The losses in the thermal pathways are unwanted as they increase the heat load into the cryostat and interfere with the measurement. To solve this challenge, a conduction-cooled cryostat with special attention in limiting eddy-current losses in the cryostat structures was constructed. The design process is illustrated in detail starting from the specifications and proceeding through the fabrication of individual components. The loss dissipated in the cryostat is experimentally examined, and the finished conduction-cooled magnetization loss measurement system is demonstrated by characterizing a multifilamentary \hbox{MgB}-{2} conductor.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Electrical Engineering, Research area: Electromagnetics, Lappeenranta University of Technology, LUT Energy, Slovak Academy of Sciences
Contributors: Järvelä, J., Lyly, M., Stenvall, A., Juntunen, R., Souc, J., Mikkonen, R.
Publication date: 1 Feb 2015
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Applied Superconductivity
Volume: 25
Issue number: 1
ISSN (Print): 1051-8223
Ratings: 
  • Scopus rating (2015): CiteScore 1.27 SJR 0.403 SNIP 1.046
Original language: English
ASJC Scopus subject areas: Electrical and Electronic Engineering, Condensed Matter Physics, Electronic, Optical and Magnetic Materials
Source: Scopus
Source ID: 84916620705

Research output: Contribution to journalArticleScientificpeer-review

Two cations, two mechanisms: Interactions of sodium and calcium with zwitterionic lipid membranes

Adsorption of metal cations onto a cellular membrane changes its properties, such as interactions with charged moieties or the propensity for membrane fusion. It is, however, unclear whether cells can regulate ion adsorption and the related functions via locally adjusting their membrane composition. We employed fluorescence techniques and computer simulations to determine how the presence of cholesterol - a key molecule inducing membrane heterogeneity - affects the adsorption of sodium and calcium onto zwitterionic phosphatidylcholine bilayers. We found that the transient adsorption of sodium is dependent on the number of phosphatidylcholine head groups, while the strong surface binding of calcium is determined by the available surface area of the membrane. Cholesterol thus does not affect sodium adsorption and only plays an indirect role in modulating the adsorption of calcium by increasing the total surface area of the membrane. These observations also indicate how lateral lipid heterogeneity can regulate various ion-induced processes including adsorption of peripheral proteins, nanoparticles, and other molecules onto membranes.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Physics, University of Helsinki, J. Heyrovský Institute of Physical Chemistry, Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic
Contributors: Javanainen, M., Melcrová, A., Magarkar, A., Jurkiewicz, P., Hof, M., Jungwirth, P., Martinez-Seara, H.
Number of pages: 4
Pages: 5380-5383
Publication date: 2017
Peer-reviewed: Yes

Publication information

Journal: Chemical Communications
Volume: 53
Issue number: 39
ISSN (Print): 1359-7345
Ratings: 
  • Scopus rating (2017): CiteScore 6.03 SJR 2.555 SNIP 1.127
Original language: English
ASJC Scopus subject areas: Catalysis, Electronic, Optical and Magnetic Materials, Ceramics and Composites, Chemistry(all), Surfaces, Coatings and Films, Metals and Alloys, Materials Chemistry
Electronic versions: 
Source: Scopus
Source ID: 85021689400

Research output: Contribution to journalArticleScientificpeer-review

Paraxial light beams in structured anisotropic media

We discuss the paraxial approximation for optical waves propagating in a uniaxial anisotropic medium inhomogeneously twisted on the plane normal to the wave vector, with the latter being parallel to one of the two principal axes normal to the optic axis. Such geometry implies a continuous power transfer between the ordinary and extraordinary components, regardless of the input beam polarization. We pinpoint that this peculiar feature, generalizable to any inhomogeneous linear birefringent material, strongly affects the application of the paraxial approximation due to the simultaneous presence of two different phase velocities. We eventually show that a local coordinate transformation permits a correct application of the paraxial approximation.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Photonics, Research group: Nonlinear Optics, Univ Porto, Universidade do Porto, Fac Med, Dept Med Imaging
Contributors: Jisha, C. P., Alberucci, A.
Number of pages: 6
Pages: 2019-2024
Publication date: 1 Nov 2017
Peer-reviewed: Yes

Publication information

Journal: Journal of the Optical Society of America A: Optics and Image Science, and Vision
Volume: 34
Issue number: 11
ISSN (Print): 1084-7529
Ratings: 
  • Scopus rating (2017): CiteScore 1.76 SJR 0.687 SNIP 1.098
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Atomic and Molecular Physics, and Optics, Computer Vision and Pattern Recognition
Source: Scopus
Source ID: 85033368214

Research output: Contribution to journalArticleScientificpeer-review

Reversible photodoping of TiO2 nanoparticles

Observations on strong photochromic effect of crystalline TiO2 quantum dots (mean size ≈ 4 nm) are presented. The synthesized quantum dots consist of irregularly shaped anatase TiO2 nanoparticles (NPs) and are dispersed in butanol (8 % by mass). Obtained NPs exhibit a dramatic photo-response to UV light, enabling effective transmittance modula-tion of in a broad wavelength range extending from visible to near-infrared region, and even the thermal black body radiation regime beyond 10 μm. The exceptional photo-response is attributed to hole-scavenging by butanol, TiO2 self-reduction, injection of electrons to the conduction band, and consequent localized surface plasmon resonances in NPs. Observed optical effect is reversible and the initial high transmittance state can be restored simply by exposing the NPs to air. Applied NP synthesis route is economic and can be easily scaled for applications such as smart window technol-ogies.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Photonics, Research group: Surface Science, Univ Tartu, University of Tartu, University of Tartu Institute of Physics, Inst Phys, University of Tartu
Contributors: Joost, U., Sutka, A., Oja, M., Smits, K., Doebelin, N., Loot, A., Järvekülg, M., Hirsimäki, M., Valden, M., Nommiste, E.
Pages: 8968-8974
Publication date: 26 Dec 2018
Peer-reviewed: Yes
Early online date: 10 Dec 2018

Publication information

Journal: Chemistry of Materials
Volume: 30
Issue number: 24
ISSN (Print): 0897-4756
Ratings: 
  • Scopus rating (2018): CiteScore 9.92 SJR 4.224 SNIP 1.797
Original language: English
ASJC Scopus subject areas: Inorganic Chemistry, Materials Chemistry, Surfaces and Interfaces, Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Keywords: tio2, nano, nanoparticle, photochromic, anatase, light, photonics, functional
URLs: 

Bibliographical note

INT=fot,"Joost, Urmas"

Research output: Contribution to journalArticleScientificpeer-review

Superfluid weight and Berezinskii-Kosterlitz-Thouless transition temperature of twisted bilayer graphene

We study superconductivity of twisted bilayer graphene with local and nonlocal attractive interactions. We obtain the superfluid weight and Berezinskii-Kosterlitz-Thouless (BKT) transition temperature for microscopic tight-binding and low-energy continuum models. We predict qualitative differences between local and nonlocal interaction schemes which could be distinguished experimentally. In the flat-band limit where the pair potential exceeds the band width we show that the superfluid weight and BKT temperature are determined by multiband processes and quantum geometry of the band.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Physics, Aalto University, University of Jyvaskyla
Contributors: Julku, A., Peltonen, T. J., Liang, L., Heikkilä, T. T., Törmä, P.
Publication date: 1 Feb 2020
Peer-reviewed: Yes

Publication information

Journal: Physical Review B
Volume: 101
Issue number: 6
Article number: 060505
ISSN (Print): 2469-9950
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics

Bibliographical note

INT=phys,"Liang, L."

Source: Scopus
Source ID: 85082866595

Research output: Contribution to journalArticleScientificpeer-review

Broadband finite-Difference Time-Domain modeling of plasmonic organic photovoltaics

We develop accurate finite-difference time-domain (FDTD) modeling of polymer bulk heterojunction solar cells containing Ag nanoparticles between the holetransporting layer and the transparent conducting oxidecoated glass substrate in the wavelength range of 300 nm to 800 nm. The Drude dispersion modeling technique is used to model the frequency dispersion behavior of Agnanoparticles, the hole-transporting layer, and indium tin oxide. The perfectly matched layer boundary condition is used for the top and bottom regions of the computational domain, and the periodic boundary condition is used for the lateral regions of the same domain. The developed FDTD modeling is employed to investigate the effect of geometrical parameters of Ag nanospheres on electromagnetic fields in devices. Although negative plasmonic effects are observed in the considered device, absorption enhancement can be achieved when favorable geometrical parameters are obtained.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Augmented Human Activities (AHA), University Seoul, Ohio State University, Ajou University
Contributors: Jung, K. Y., Yoon, W. J., Park, Y. B., Berger, P. R., Teixeira, F. L.
Number of pages: 8
Pages: 654-661
Publication date: 2014
Peer-reviewed: Yes

Publication information

Journal: ETRI Journal
Volume: 36
Issue number: 4
ISSN (Print): 1225-6463
Ratings: 
  • Scopus rating (2014): CiteScore 1.45 SJR 0.442 SNIP 1.395
Original language: English
ASJC Scopus subject areas: Electrical and Electronic Engineering, Computer Science(all), Electronic, Optical and Magnetic Materials
Keywords: FDTD, Organic photovoltaics, Plasmonics
Source: Scopus
Source ID: 84905972119

Research output: Contribution to journalArticleScientificpeer-review

MECSELs with direct emission in the 760 nm to 810 nm spectral range: A single- and double-side pumping comparison and high-power continuous-wave operation

We compared single-side pumping (SSP) and double-side pumping (DSP) of a semiconductor membrane external-cavity surface-emitting laser (MECSEL). The MECSEL's active region was based on a 4×3 AlGaAs quantum well (QW) structure. This structure was embedded between two silicon carbide (SiC) wafer pieces that were used as transparent intra-cavity (IC) heat spreaders creating a symmetrical cooling environment. The MECSEL structure targeted emission at 780nm and was operated at 20°C heat sink temperature. Via DSP the differential efficiency was improved from 31.9% to 34.4 %. The laser threshold was reduced from 0.79 W to 0.69 W of absorbed pump power while the maximum output power was increased from 3.13 W to 3.22 W. The DSP configuration enabled these improvements by a reduced thermal resistance of the gain element by 9 %. The MECSEL operated at a fundamental Gaussian TEM00 mode profile and the beam quality was measured to be M2 <1.09. We further demonstrate a maximum tuning range from 767 nm to 811 nm. A similar active region with about half the thickness (2×3 AlGaAs QWs) was investigated using the DSP configuration and first results are presented here. 500-μm-thick sapphire IC heat spreaders were used instead of SiC. The output power exceeded 0.5W and the emission was spectrally located around 770 nm.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Physics
Contributors: Kahle, H., Penttinen, J. P., Phung, H. M., Rajala, P., Tukiainen, A., Ranta, S., Guina, M.
Publication date: 2019

Host publication information

Title of host publication: Vertical External Cavity Surface Emitting Lasers (VECSELs) IX
Publisher: SPIE, IEEE
Editor: Keller, U.
Article number: 109010D
ISBN (Electronic): 9781510624443

Publication series

Name: Proceedings of SPIE - The International Society for Optical Engineering
Volume: 10901
ISSN (Print): 0277-786X
ISSN (Electronic): 1996-756X
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Computer Science Applications, Applied Mathematics, Electrical and Electronic Engineering
Keywords: AlGaAs, DBR-free, MECSEL, Near infra-red, Thermal management, Thermal resistance, VECSEL

Bibliographical note

INT=phys,"Rajala, Patrik"
jufoid=71479

Source: Scopus
Source ID: 85066635597

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Double-side pumped membrane external-cavity surface-emitting laser (MECSEL) with increased efficiency emitting > 3 W in the 780 nm region

We demonstrate a double-side pumped MECSEL emitting more than 3 W of output power in the 780 nm wavelength region. The laser exhibits an efficiency as high as 34.4 %.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Physics
Contributors: Kahle, H., Phung, H., Penttinen, J., Rajala, P., Tukiainen, A., Ranta, S., Guina, M.
Publication date: 1 May 2019

Host publication information

Title of host publication: 2019 Conference on Lasers and Electro-Optics, CLEO 2019 - Proceedings
Publisher: IEEE
ISBN (Electronic): 9781943580576
ASJC Scopus subject areas: Spectroscopy, Industrial and Manufacturing Engineering, Safety, Risk, Reliability and Quality, Management, Monitoring, Policy and Law, Electronic, Optical and Magnetic Materials, Radiology Nuclear Medicine and imaging, Instrumentation, Atomic and Molecular Physics, and Optics

Bibliographical note

INT=phys,"Rajala, Patrik"

Source: Scopus
Source ID: 85069191246

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Crystallization processes in the phase change material Ge2 Sb2 Te5: Unbiased density functional/molecular dynamics simulations

Three extensive density functional/molecular dynamics simulations of the crystallization of amorphous Ge2Sb2Te5 (460 atoms) [Phys. Rev. B 90, 184109 (2014)PRBMDO1098-012110.1103/PhysRevB.90.184109] have been completed with simulation times of up to 8.2 ns. Together with the results of earlier simulations with and without a crystallite seed, the results clarify essential features of a complicated process. They emphasize, in particular, the stochastic nature of crystallization, the effect of bond orientations and percolation, and the importance of extended simulations of sufficiently large samples. This is particularly evident in describing the role of crystallites that can merge to form larger units or hinder complete crystallization by the formation of grain boundaries. The total pair distribution functions for the final structures are compared with available neutron and x-ray diffraction data.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Physics, Singapore University of Technology and Design, COMP Centre of Excellence, Aalto University, Forschungszentrum Jülich (FZJ)
Contributors: Kalikka, J., Akola, J., Jones, R. O.
Publication date: 17 Oct 2016
Peer-reviewed: Yes

Publication information

Journal: Physical Review B
Volume: 94
Issue number: 13
Article number: 134105
ISSN (Print): 1098-0121
Ratings: 
  • Scopus rating (2016): CiteScore 3.16 SJR 2.339 SNIP 1.183
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Source: Scopus
Source ID: 84992161291

Research output: Contribution to journalArticleScientificpeer-review

Are coarse-grained models apt to detect protein thermal stability? the case of OPEP force field

We present the first investigation of the kinetic and thermodynamic stability of two homologous thermophilic and mesophilic proteins based on the coarse-grained model OPEP. The object of our investigation is a pair of G-domains of relatively large size, 200 amino acids each, with an experimental stability gap of about 40 K. The OPEP force field is able to maintain stable the fold of these relatively large proteins within the hundred-nanosecond time scale without including external constraints. This makes possible to characterize the conformational landscape of the folded protein as well as to explore the unfolding. In agreement with all-atom simulations used as a reference, we show that the conformational landscape of the thermophilic protein is characterized by a larger number of substates with slower dynamics on the network of states and more resilient to temperature increase. Moreover, we verify the stability gap between the two proteins using replica-exchange simulations and estimate a difference between the melting temperatures of about 23 K, in fair agreement with experiment. The detailed investigation of the unfolding thermodynamics allows to gain insight into the mechanism underlying the enhanced stability of the thermophile relating it to a smaller heat capacity of unfolding.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Multi-scaled biodata analysis and modelling (MultiBAM), Laboratoire de Biochimie Théorique, Institut Universitaire de France
Contributors: Kalimeri, M., Derreumaux, P., Sterpone, F.
Number of pages: 8
Pages: 494-501
Publication date: 1 Jan 2015
Peer-reviewed: Yes

Publication information

Journal: Journal of Non-Crystalline Solids
Volume: 407
ISSN (Print): 0022-3093
Ratings: 
  • Scopus rating (2015): CiteScore 1.85 SJR 0.663 SNIP 1.083
Original language: English
ASJC Scopus subject areas: Condensed Matter Physics, Ceramics and Composites, Electronic, Optical and Magnetic Materials, Materials Chemistry
Keywords: Coarse-grained force field, Conformational substates network, Molecular dynamics, Protein thermodynamic stability, Thermophilic proteins
Source: Scopus
Source ID: 84922435805

Research output: Contribution to journalArticleScientificpeer-review

Narrow-linewidth operation of folded VECSEL cavity with twist-mode configuration

VECSELs exhibit much different longitudinal mode behavior when the device is placed at a fold of a standing wave cavity. Lasing spectrum can be narrowed by employing mode-twisting, stabilizing the standing-wave pattern at the VECSEL.

General information

Publication status: Published
MoE publication type: Not Eligible
Organisations: University of Arizona, Hart SCI, Vexlum Ltd.
Contributors: Kaneda, Y., Hart, M. L., Warner, S. H., Penttinen, J. P., Guina, M.
Number of pages: 2
Publication date: 2018
Peer-reviewed: Unknown
Event: Paper presented at Advanced Solid State Lasers, ASSL 2018, Boston, United States.
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Mechanics of Materials
Source: Scopus
Source ID: 85059479588

Research output: Other conference contributionPaper, poster or abstractScientific

Evaluation of crushing strength of spray-dried MgAl2O4 granule beds

The crushing strengths of four different experimental magnesium aluminate spinel (MgAl2O4) granule beds were monitored with the axial die pressing test after heat treatments. Precursor, magnesium hydroxide (Mg(OH)2) and magnesium oxide (MgO) as Mg precursor and aluminium oxide hydroxide Al(O)OH and α-Al2O3 as Al precursor, were used for experimental granules, which were manufactured via a dispersion manufacturing and spray-drying process. After spray-drying, granules were heat treated in air at 1000, 1100, 1200, 1300 and 1400 °C. In order to understand the potential effect of precursor, phase structure, morphology, particle size distribution and density of granules on crushing strength behaviour, scanning X-ray diffraction (XRD) was used together with electron microscopy (SEM) and laser diffraction (LDPA) for characterisation. All precursor mixtures formed spherical granules during the spray-drying process and pure spinel phase structure during heat treatment. The crushing strength test results indicated that the Al precursor clearly affected the crushing strength behaviour of experimental granule beds. The highest strength was observed for granule beds with Al(O)OH) as Al and Mg(OH)2 as Mg precursor.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Materials Science, Engineering materials science and solutions (EMASS), VTT Technical Research Centre of Finland
Contributors: Kanerva, U., Suhonen, T., Lagerbom, J., Levänen, E.
Number of pages: 7
Pages: 8494-8500
Publication date: 1 Aug 2015
Peer-reviewed: Yes

Publication information

Journal: Ceramics International
Volume: 41
Issue number: 7
ISSN (Print): 0272-8842
Ratings: 
  • Scopus rating (2015): CiteScore 2.64 SJR 0.823 SNIP 1.353
Original language: English
ASJC Scopus subject areas: Ceramics and Composites, Process Chemistry and Technology, Electronic, Optical and Magnetic Materials, Surfaces, Coatings and Films, Materials Chemistry
Keywords: Axial pressing, Granule, MgAl<inf>2</inf>O<inf>4</inf> spinel, The crushing strength

Bibliographical note

EXT="Lagerbom, Juha"
EXT="Kanerva, Ulla"

Source: Scopus
Source ID: 84929271760

Research output: Contribution to journalArticleScientificpeer-review

Pulsed high-power yellow-orange VECSEL

We report on the development of a pulsed high-power frequency doubled vertical-external-cavity surface-emitting laser (VECSEL) with a peak output power of 14 W and emission spectrum near 588 nm. The semiconductor gain chip was grown by molecular beam epitaxy and comprised 10 GaInAs quantum wells. The gain structure was designed to be antiresonant at 1180 nm. The fundamental wavelength was frequency doubled to the yellow-orange spectral range using a 10-mm long critically phase matched lithium triborate nonlinear crystal, situated at the mode waist of the V-shaped laser cavity. The emission spectrum was narrowed down to FWHM of < 0.2 nm by employing a 1.5 mm birefringent filter and a 100-μm-thick etalon inside the cavity. By directly modulating the pump laser of the VECSEL, we were able to produce pulse widths down to 570 ns with average and peak output power of 81 mW and 14 W, respectively. The repetition rate was kept constant at 10 kHz throughout the measurements. The maximum peak power obtained was pump power limited. In comparison, at the same coolant temperature, a maximum of 8.5 W was achieved in continuous wave. The maximum optical-to-optical conversion efficiency (absorbed peak pump power to peak output power) was calculated to be 20-21 %. © 2014 SPIE.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Optoelectronics Research Centre, Research group: Semiconductor Technology and Applications, Frontier Photonics, Optoelectronics Research Centre, Tampere University of Technology
Contributors: Kantola, E., Leinonen, T., Ranta, S., Tavast, M., Guina, M.
Publication date: 2014

Host publication information

Title of host publication: Photonics Europe 2014, Semiconductor Lasers and Laser Dynamics VI, April 14-17, 2014, Brussels, Belgium. Proceedings of SPIE
Volume: 9134
Publisher: SPIE
Article number: 91340Z
ISBN (Print): 978-1-6284-1090-7

Publication series

Name: SPIE Conference Proceedings
Volume: 9134
ISSN (Print): 0277-786X
ISSN (Electronic): 1996-756X
ASJC Scopus subject areas: Applied Mathematics, Computer Science Applications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Keywords: Frequency doubling, Gain modulation, High-efficiency, High-power, Pulsed, SHG, Yellow-orange VECSEL

Bibliographical note

Contribution: organisation=orc,FACT1=1<br/>Portfolio EDEND: 2014-08-31<br/>Publisher name: SPIE - International Society for Optical Engineering

Source: researchoutputwizard
Source ID: 654

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

1180nm VECSEL with 50 W output power

We report on the development of a high-power vertical-external-cavity surface-emitting laser (VECSEL) emitting around 1180 nm. The laser emitted 50 W of output power when the mount of the gain chip was cooled to -15°C. The output power was measured using a 97% reflective cavity end-mirror. The VECSEL was arranged to form an I-shaped cavity with a length of ∼100 mm; the gain chip and a curved dielectric mirror (RoC=150) acting as cavity end mirrors. The gain chip was grown by molecular beam epitaxy (MBE) and incorporated 10 GaInAs/GaAs quantum wells. For efficient heat extraction, the chip was capillary bonded to a diamond heat spreader which was attached to a TEC-cooled copper mount. The maximum optical-to-optical conversion efficiency of 28% was achieved for 42 W of output power and -15°C mount temperature.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Optoelectronics Research Centre, Research group: Semiconductor Technology and Applications, Frontier Photonics
Contributors: Kantola, E., Leinonen, T., Ranta, S., Tavast, M., Penttinen, J., Guina, M.
Publication date: 2015

Host publication information

Title of host publication: Proceedings of SPIE - The International Society for Optical Engineering
Volume: 9349
Publisher: SPIE
Article number: 93490U
ISBN (Print): 9781628414394
ASJC Scopus subject areas: Applied Mathematics, Computer Science Applications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Keywords: continuous wave, frequency doubling, heat management, high power, infrared, power scaling, SDL, VECSEL
Source: Scopus
Source ID: 84925666801

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Molecular dynamics simulations for Xe absorbed in zeolites

We have carried out molecular dynamics simulations for Xe atoms absorbed in two different zeolites, NaA and AlPO-11. The main emphasis is in the distribution of Xe in the zeolites, Xe-Xen interactions in NaA, and structural data on Xe-zeolite cage interactions. We report single-particle and pair correlation data, along with diffusion constants of Xe at 300 K. NMR chemical shifts of Xe were estimated using ab initio parametrization.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: University of Oulu
Contributors: Kantola, J. H., Vaara, J., Rantala, T. T., Jokisaari, J.
Number of pages: 6
Pages: 599-604
Publication date: 1996

Host publication information

Title of host publication: Materials Research Society Symposium - Proceedings
Volume: 408
Publisher: MATERIALS RESEARCH SOCIETY
Editors: Kaxiras, E., Joannopoulos, J., Vashishta, P., Kalia, R. K.
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials
Source: Scopus
Source ID: 0030315761

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Frequency-doubled VECSEL employing a Volume Bragg Grating for linewidth narrowing

We report on a frequency-doubled VECSEL emitting at 512.6 nm. The laser spectrum was narrowed with a Volume Bragg Grating and the intracavity frequency-doubling was achieved with a periodically poled MgO-doped lithium niobate.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Photonics
Contributors: Kantola, E., Penttinen, J., Leinonen, T., Ranta, S., Guina, M.
Publication date: 2018

Host publication information

Title of host publication: CLEO : Applications and Technology, CLEO_AT 2018
Publisher: OSA - The Optical Society
ISBN (Electronic): 9781557528209
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Mechanics of Materials
Source: Scopus
Source ID: 85052561135

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Frequency-doubled wafer-fused 638 nm VECSEL with an output power of 5.6 W

We report on a frequency doubled vertical-external-cavity surface-emitting laser emitting 5.6 W at 635 nm. The cavity employed a wafer-fused AlInGaAs/InP-AlAs/GaAs gain mirror in a V-shaped configuration. The heatsink temperature was 20 °C.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Photonics, RTI-Research SA
Contributors: Kantola, E., Leinonen, T., Rantamäki, A., Guina, M., Sirbu, A., Iakovlev, V.
Publication date: 2018

Host publication information

Title of host publication: CLEO : Applications and Technology, CLEO_AT 2018
Publisher: OSA - The Optical Society
ISBN (Electronic): 9781557528209
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Mechanics of Materials
Source: Scopus
Source ID: 85049146963

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Effect of sol-gel derived in situ silica on the morphology and mechanical behavior of natural rubber and acrylonitrile butadiene rubber blends

Silica particles were generated and grown in situ by sol-gel method into rubber blends comprised of natural rubber (NR) and acrylonitrile butadiene rubber (NBR) at various blend ratios. Silica formed into rubber matrix was amorphous in nature. Amount of in situ silica increased with increase in natural rubber proportion in the blends during the sol-gel process. Morphology studies showed that the generated in situ silica were nanoparticles of different shapes and sizes mostly grown into the NR phase of the blends. In situ silica filled NR/NBR blend composites showed improvement in the mechanical and dynamic mechanical behaviors in comparison to those of the unfilled and externally filled NR/ NBR blend composites. For the NR/NBR blend at 40/60 composition, in particular, the improvement was appreciable where size and dispersion of the silica particles into the rubber matrix were found to be more uniform. Dynamic mechanical analysis revealed a strong rubber-in situ silica interaction as indicated by a positive shift of the glass transition temperature of both the rubber phases in the blends.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Engineering materials science and solutions (EMASS), Visvesvaraya National Institute of Technology, Leibniz-Institut für Polymerforschung Dresden E.V.
Contributors: Kapgate, B. P., Das, C., Das, A., Basu, D., Reuter, U., Heinrich, G.
Number of pages: 9
Pages: 501-509
Publication date: Sep 2012
Peer-reviewed: Yes

Publication information

Journal: JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY
Volume: 63
Issue number: 3
ISSN (Print): 0928-0707
Ratings: 
  • Scopus rating (2012): CiteScore 1.82 SJR 0.732 SNIP 1.133
Original language: English
ASJC Scopus subject areas: Chemistry(all), Condensed Matter Physics, Biomaterials, Ceramics and Composites, Electronic, Optical and Magnetic Materials, Materials Chemistry
Keywords: In situ silica, Reinforcement, Rubber blend, Rubber-filler interaction, Sol-gel
Source: Scopus
Source ID: 84875426374

Research output: Contribution to journalArticleScientificpeer-review

Mining tailings as raw materials for reaction-sintered aluminosilicate ceramics: Effect of mineralogical composition on microstructure and properties

This paper presents studies on the utilization of aluminosilicate-based mining tailings as raw materials for mullite-based ceramics. Based on the 3:2 stoichiometric composition, mullite was synthesised by reactive sintering with a series of powder mixtures with alumina additions. X-ray diffractometry and scanning electron microscopy analyses revealed that, at the specific mineralogical composition, mullite structure formed surrounded by an amorphous glass phase in reaction-sintered powder mixtures. Results demonstrated that the chemical and mineralogical composition of mining tailings do have an effect on mullite formation possibilities and, only with the particular mineralogical composition, the mullite formation is possible regardless of the correct Al:Si ratio in tailings. Physical and mechanical properties of the formed ceramics were defined, showing comparable values to 3:2 mullite reference. Mullite structure formation enables a better thermal resistance up to above 1450 °C of the formed tailings-based ceramics compared to other aluminosilicates, reflecting their utilization potential for refractory ceramic applications.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Materials Science, Research group: Materials Characterization, VTT Technical Research Centre of Finland, Geologian tutkimuskeskus
Contributors: Karhu, M., Lagerbom, J., Solismaa, S., Honkanen, M., Ismailov, A., Räisänen, M. L., Huttunen-Saarivirta, E., Levänen, E., Kivikytö-Reponen, P.
Pages: 4840-4848
Publication date: Mar 2019
Peer-reviewed: Yes
Early online date: 2018

Publication information

Journal: Ceramics International
Volume: 45
Issue number: 4
ISSN (Print): 0272-8842
Ratings: 
  • Scopus rating (2019): SJR 0.891 SNIP 1.31
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Ceramics and Composites, Process Chemistry and Technology, Surfaces, Coatings and Films, Materials Chemistry
Keywords: Mining tailings, Mullite, Reaction sintering, Refractory ceramics, Utilization

Bibliographical note

EXT="Lagerbom, Juha"

Source: Scopus
Source ID: 85057276435

Research output: Contribution to journalArticleScientificpeer-review

ATM switch for 2.488 Gbit/s CATV network on FPGA with a high-throughput buffering architecture

This paper presents an ATM switch with a high-throughput buffering architecture and a new performance measurement system. The switch has been designed for multiplexing and routing Digital Video Broadcasting (DVB) services over 2.488 Gbits/s Asynchronous Transfer Mode (ATM) Cable TV (CATV) backbone network. The buffering architecture is based on a crossbar switch with internal buffering but it also has features of shared memory and output buffered switches. In addition to the buffering architecture the high throughput of this switch is based on an adaptive arbitration algorithm that is used to schedule the transfers of the cells from the cross-point buffers to the output buffers. This adaptive algorithm, which is a combination of Round Robin (RR) and Longest Queue First Served (LQFS) algorithms, provides starvation free service for the buffers with a small cell loss rate. Due to the internal buffering it was possible to use distributed arbitration that can easier achieve a high operation rate than one centralized arbiter. This paper also shows a quick and easy way of analyzing the performance of the presented ATM switch architecture. The high throughput of the switch has also been verified using a new method of measuring the probability distribution of the filling of the buffers of the switch. Additionally this paper deals with a few implementation aspects, since the control logic and the internally buffered crossbar are implemented on a Field Programmable Gate Array (FPGA) circuit.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Research group: System-on-Chip for GNSS, Wireless Communications and Cyber-Physical Embedded Computing, Teleste Corporation
Contributors: Kariniemi, H., Nurmi, J., Fagerlund, P., Liitola, J., Alinikula, J.
Publication date: 2002

Host publication information

Title of host publication: Midwest Symposium on Circuits and Systems
Volume: 2
ASJC Scopus subject areas: Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials
Source: Scopus
Source ID: 0036979380

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Integrated multi-wavelength mid-IR light source for gas sensing

Cost effective multi-wavelength light sources are key enablers for spectroscopic applications at Mid-IR wavelength range. Utilizing a novel Mid-IR Si-based photonic integrated circuit filter and wide-band Mid-IR SLEDs, we show the concept of a light source that covers 2.7.3.5 μm wavelength range with a resolution <1nm. The spectral bands are switchable and tunable and they can be modulated. The source allows for the fabrication of an affordable multi-band gas sensor with good selectivity and sensitivity. The unit price can be lowered in high volumes by utilizing tailored molded IR lens technology and automated packaging and assembling technologies. The status of the development of the key components of the light source are reported. The Mid-IR PIC is based on the use of thick-SOI technology, SLED is based on AlGaInAsSb materials and the lenses are tailored single crystal, nonoxide glass and heavy metal oxide glasses fabricated by the use of hot-embossing. The packaging concept utilizing automated assembly tools are depicted. In safety and security applications, the Mid-IR wavelength range covered by the source allows for the detection of several harmful gas components with a single sensor. At the moment, affordable sources are not available. The market impact is expected to be disruptive, since the devices currently in the market are either complicated, expensive and heavy instruments, or the applied measurement principles are inadequate in terms of stability and selectivity.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Photonics, Research group: ORC, VTT Technical Research Centre of Finland, Institute of Electronic Materials Technology, Vaisala Oyj, Airoptic Sp. z o.o., GasSecure, VIGO System S.A.
Contributors: Karioja, P., Alajoki, T., Cherchi, M., Ollila, J., Harjanne, M., Heinilehto, N., Suomalainen, S., Zia, N., Tuorila, H., Viheriälä, J., Guina, M., Buczynski, R., Kasztelanic, R., Salo, T., Virtanen, S., Kluczynski, P., Borgen, L., Ratajczyk, M., Kalinowski, P.
Publication date: 2018

Host publication information

Title of host publication: Next-Generation Spectroscopic Technologies XI
Publisher: SPIE, IEEE
Article number: 106570A
ISBN (Electronic): 9781510618251

Publication series

Name: SPIE Conference Proceedings
Volume: 10657
ISSN (Print): 0277-786X
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Computer Science Applications, Applied Mathematics, Electrical and Electronic Engineering
Keywords: gas sensing, Mid-IR integrated optics, Mid-IR lens, photonics packaging, PIC, Si photonics, SLED

Bibliographical note

jufoid=71479

Source: Scopus
Source ID: 85050701514

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Computational super-resolution phase retrieval from multiple phase-coded diffraction patterns: Simulation study and experiments

In this paper, we consider computational super-resolution inverse diffraction phase retrieval. The optical setup is lensless, with a spatial light modulator for aperture phase coding. The paper is focused on experimental tests of the super-resolution sparse phase amplitude retrieval algorithm. We start from simulations and proceed to physical experiments. Both simulation tests and experiments demonstrate good-quality imaging for super-resolution with a factor of 4 and a serious advantage over diffraction-limited resolution as defined by Abbe’s criterion.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Signal Processing, Research group: Computational Imaging-CI, Department of Photonics and Optical Information Technology, ITMO University
Contributors: Katkovnik, V., Shevkunov, I., Petrov, N. V., Egiazarian, K.
Number of pages: 9
Pages: 786-794
Publication date: 20 Jul 2017
Peer-reviewed: Yes

Publication information

Journal: Optica
Volume: 4
Issue number: 7
ISSN (Print): 2334-2536
Ratings: 
  • Scopus rating (2017): CiteScore 9.05 SJR 4.602 SNIP 2.811
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Atomic and Molecular Physics, and Optics
Keywords: Discrete optical signal processing, Image processing, Noise in imaging systems, Phase retrieval, Superresolution
Source: Scopus
Source ID: 85025162894

Research output: Contribution to journalArticleScientificpeer-review

Computational wavelength resolution for in-line lensless holography: Phase-coded diffraction patterns and wavefront group-sparsity

In-line lensless holography is considered with a random phase modulation at the object plane. The forward wavefront propagation is modelled using the Fourier transform with the angular spectrum transfer function. The multiple intensities (holograms) recorded by the sensor are random due to the random phase modulation and noisy with Poissonian noise distribution. It is shown by computational experiments that high-accuracy reconstructions can be achieved with resolution going up to the two thirds of the wavelength. With respect to the sensor pixel size it is a super-resolution with a factor of 32. The algorithm designed for optimal superresolution phase/amplitude reconstruction from Poissonian data is based on the general methodology developed for phase retrieval with a pixel-wise resolution in V. Katkovnik, "Phase retrieval from noisy data based on sparse approximation of object phase and amplitude", http://www.cs.tut.fi/∼lasip/DDT/index3.html.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Signal Processing, Department of Photonics and Optical Information Technology, ITMO University
Contributors: Katkovnik, V., Shevkunov, I., Petrov, N. V., Egiazarian, K.
Publication date: 2017

Host publication information

Title of host publication: Digital Optical Technologies 2017
Publisher: SPIE
Article number: 1033509
ISBN (Electronic): 9781510611153

Publication series

Name: Proceedings of SPIE
Volume: 10335
ISSN (Print): 0277-786X
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Computer Science Applications, Applied Mathematics, Electrical and Electronic Engineering
Keywords: Discrete optical signal processing, Image processing, Noise in imaging systems, Phase retrieval, Superresolution

Bibliographical note

jufoid=71479

Source: Scopus
Source ID: 85030715279

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Multiwavelength surface contouring from phase-coded diffraction patterns

We propose a new algorithm for absolute phase retrieval from multiwavelength noisy phase coded diffraction patterns in the task of surface contouring. A lensless optical setup is considered with a set of successive single wavelength experiments. The phase masks are applied for modulation of the multiwavelength object wavefronts. The algorithm uses the forward and backward propagation for coherent light beams and sparsely encoding wavefronts which leads to the complex-domain block-matching 3D filtering. The key-element of the algorithm is an original aggregation of the multiwavelength object wavefronts for high-dynamic-range profile measurement. Numerical experiments demonstrate that the developed approach leads to the effective solutions explicitly using the sparsity for noise suppression and high-accuracy object profile reconstruction.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Signal Processing, Research group: Computational Imaging-CI, ITMO University
Contributors: Katkovnik, V., Shevkunov, I., Petrov, N. V., Eguiazarian, K.
Publication date: 1 Jan 2018

Host publication information

Title of host publication: Unconventional Optical Imaging 2018. Strasbourg, France
Publisher: SPIE
Article number: 106771B
ISBN (Print): 978-1-5106-1880-0

Publication series

Name: Proceedings of SPIE - The International Society for Optical Engineering
Volume: 10677
ISSN (Electronic): 0277-786X
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Computer Science Applications, Applied Mathematics, Electrical and Electronic Engineering
Keywords: absolute phase retrieval, discrete optical signal processing, Multiwavelength phase retrieval, phase imaging, surface contouring
Source: Scopus
Source ID: 85052446644

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

The effect of carbon and nickel additions on the precursor synthesis of Cr3C2-Ni nanopowder

Decreasing crystal size to nanoscale is a proven method to enhance material properties. In this study, nanosize Cr3C2 and Cr3C2-Ni were synthetized and the reaction sequence was studied. Aqueous precursors using only water-soluble raw materials with varying carbon contents and a nickel addition were spray-dried. Glycine was used as a carbon source and chromium acetate hydroxide as a chromium source in the precursor solutions. Nickel nitrate hexahydrate was introduced as a nickel source to yield a metallic binder into the carbide nanopowder.Resulting powders were heat-treating to identify an applicable precursor composition producing the targeted Cr3C2 phase with crystal size of tens of nanometers. Thermal synthesis tests of the precursor powders to yield Cr3C2 took place at a temperature between 900 and 1300 °C under an Argon atmosphere. The synthesis of nanosize Cr3C2-Ni powder was successful at 1000 °C in 30 min, in a case of the best precursor. In order to produce the carbide phase with no residual oxide traces, relative carbon load has to be 48 wt%, while the stoichiometric amount of carbon in Cr3C2 is 13 wt%. When also introducing the nickel source into the precursor, an even higher carbon load was required. The carbon surplus needed to enable the Cr3C2 synthesis attributes to the non-homogeneity of the precursor composition.The chemical synthesis starting from water-soluble raw materials is a promising way of preparing nanosize Cr3C2-Ni with the targeted phase configuration.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Materials Science, Research group: Materials Characterization, VTT Technical Research Centre of Finland
Contributors: Kaunisto, K., Kotilainen, M., Karhu, M., Lagerbom, J., Vuorinen, T., Honkanen, M., Vippola, M., Turunen, E.
Pages: 9338-9346
Publication date: 1 Jun 2018
Peer-reviewed: Yes
Early online date: 2018

Publication information

Journal: Ceramics International
Volume: 44
Issue number: 8
ISSN (Print): 0272-8842
Ratings: 
  • Scopus rating (2018): CiteScore 3.5 SJR 0.888 SNIP 1.297
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Ceramics and Composites, Process Chemistry and Technology, Surfaces, Coatings and Films, Materials Chemistry
Keywords: A. Nanosize CrC synthesis, A. Powders: chemical preparation, B. Grain size, D. Carbides, E. Wear parts

Bibliographical note

EXT="Vuorinen, Tommi"
EXT="Lagerbom, Juha"
EXT="Kaunisto, Kimmo"

Source: Scopus
Source ID: 85042300396

Research output: Contribution to journalArticleScientificpeer-review

Alpha radiation induced luminescence in solar blind spectral region

Intense luminescence in the solar blind spectral region is produced by modifying the gas atmosphere around an alpha emitter. This enables standoffdetection of alpha radiation under daylight conditions.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Physics, Photonics, Helsinki Institute of Physics
Contributors: Kerst, T., Toivonen, J.
Publication date: 2018

Host publication information

Title of host publication: CLEO : Applications and Technology, CLEO_AT 2018
Publisher: OSA - The Optical Society
ISBN (Electronic): 9781557528209
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Mechanics of Materials
Source: Scopus
Source ID: 85049133557

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Fabrication of ssDNA/oligo(ethylene glycol) monolayers by promoted exchange reaction with thiol and disulfide substituents

Biorepulsive oligo(ethylene glycol)-substituted alkanethiolate (OEG-AT) monolayers on gold can serve as primary templates for promoted (by electron irradiation) exchange reaction with thiolated ssDNA species, resulting in the formation of mixed OEG-AT/ssDNA monolayers of desired composition. Here we test the ability of alternative, disulfide precursors to serve as substituents in such a reaction. Two representative molecules, based on adenine-based homo-oligonucleotide (25-mer), were used, viz., asymmetric disulfide with a short second chain (A25SSOH) and symmetric disulfide (A25SSA25). The results were compared to the reference system of thiolated ssDNA (A25SH). Both disulfide precursors were found to be suitable for the reaction, further extending the types of commercially available compounds which can be used for this approach. A25SSOH exhibited quite high efficiency, similar to A25SH, while the efficiency of A25SSA25 was noticeably lower, especially at low irradiation doses (2). Also, the single component, A25SSA25-based ssDNA monolayer, was of lower quality as compared to the films prepared from the A25SH and A25SSOH precursors. The above observations were explained by the bulky character and conformational flexibility of A25SSA25, which hinder the proper assembly and efficient exchange reaction.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Integrated Technologies for Tissue Engineering Research (ITTE), Universitat Heidelberg
Contributors: Khan, M. N., Zharnikov, M.
Number of pages: 9
Pages: 3093-3101
Publication date: 13 Feb 2014
Peer-reviewed: Yes

Publication information

Journal: Journal of Physical Chemistry C
Volume: 118
Issue number: 6
ISSN (Print): 1932-7447
Ratings: 
  • Scopus rating (2014): CiteScore 5.08 SJR 2.032 SNIP 1.434
Original language: English
ASJC Scopus subject areas: Physical and Theoretical Chemistry, Electronic, Optical and Magnetic Materials, Surfaces, Coatings and Films, Energy(all)
Source: Scopus
Source ID: 84894037828

Research output: Contribution to journalArticleScientificpeer-review

Fabrication of ssDNA/Oligo(ethylene glycol) monolayers and patterns by exchange reaction promoted by ultraviolet light irradiation

Using a representative test system, we present here a versatile approach to prepare mixed monolayers of thiolated single-stranded DNA (ssDNA) and oligo(ethylene glycol) substituted alkanethiols (OEG-AT) in a broad range of compositions as well as ssDNA/OEG-AT patterns of desired shape imbedded into a biorepulsive background. The procedure involves two steps. First, a primary, well-defined OEG-AT monolayer on a solid support is exposed to UV light in either homogeneous or lithographic fashion. Second, the exchange reaction between the damaged OEG-AT species in the film and ssDNA substituents in solution occurs, resulting in formation of ssDNA/OEG-AT monolayer or pattern. The above procedure relies on commercially available compounds and does not require vacuum, which simplifies its application in research and industrial laboratories. The composition of the mixed films or ssDNA/OEG-AT spots (lithography) can be precisely adjusted by UV dose in an almost entire composition range. It was demonstrated that the procedure can be performed with UV light of different wavelengths (254 or 365 nm), which opens new possibilities for lithography. Using advanced spectroscopic tools, it was shown that ssDNA molecules imbedded into the OEG-AT matrix maintain their identity and intact character as well as exhibit predominant upright orientation typical of one-component films of thiolated ssDNA. The OEG-AT constituents of the mixed monolayers were found to be intact as well, with all UV damaged OEG-AT species being exchanged for ssDNA. Finally, a representative ssDNA/OEG-AT pattern was fabricated.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Integrated Technologies for Tissue Engineering Research (ITTE), Universitat Heidelberg
Contributors: Khan, M. N., Zharnikov, M.
Number of pages: 11
Pages: 24883-24893
Publication date: 27 Nov 2013
Peer-reviewed: Yes

Publication information

Journal: Journal of Physical Chemistry C
Volume: 117
Issue number: 47
ISSN (Print): 1932-7447
Ratings: 
  • Scopus rating (2013): CiteScore 5.14 SJR 2.143 SNIP 1.432
Original language: English
ASJC Scopus subject areas: Physical and Theoretical Chemistry, Electronic, Optical and Magnetic Materials, Surfaces, Coatings and Films, Energy(all)
Source: Scopus
Source ID: 84889582340

Research output: Contribution to journalArticleScientificpeer-review

Irradiation promoted exchange reaction with disulfide substituents

Exchange reaction between the primary self-assembled monolayer (SAM) on gold and potential molecular substituents capable of forming a SAM on the same substrate can be promoted by electron irradiation. Here we demonstrate that such a promoted reaction can be performed not only with thiols but with disulfides as substituents as well. This extends significantly the assortments of the suitable compounds, resulting in a broader variety of mixed SAMs and chemical patterns which can be fabricated by this technique. The kinetics of the promoted exchange reaction was studied in detail. The feasibility and practical usefulness of the approach were demonstrated by the experiments with a disulfide substituent bearing a tail group which can serve as an initiator for surface-initiated polymerization. A variety of complex polymer brush patterns was prepared using several representative polymers, relevant for biomedical research and applications, as test systems.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Integrated Technologies for Tissue Engineering Research (ITTE), Universitat Heidelberg
Contributors: Khan, M. N., Zharnikov, M.
Number of pages: 10
Pages: 14534-14543
Publication date: 18 Jul 2013
Peer-reviewed: Yes

Publication information

Journal: Journal of Physical Chemistry C
Volume: 117
Issue number: 28
ISSN (Print): 1932-7447
Ratings: 
  • Scopus rating (2013): CiteScore 5.14 SJR 2.143 SNIP 1.432
Original language: English
ASJC Scopus subject areas: Physical and Theoretical Chemistry, Electronic, Optical and Magnetic Materials, Surfaces, Coatings and Films, Energy(all)
Source: Scopus
Source ID: 84880559790

Research output: Contribution to journalArticleScientificpeer-review

Fabrication Challenges in Embedding of Components and Embroidered Conductors into 3D-printed Textile Electronics Structures

The challenging unobtrusive implementation of electronics structures into clothing, with low cost and high reliability, can be achieved via utilising and adapting a novel structural additive manufacturing method. Our goal is to utilize 3D-printed flexible and washable wireless platforms, where electronics, embroidered antennas and interconnections are embedded mid-printing, created directly on textiles. During the fabrication process, several challenges were encountered. The most important challenges related to the embroidery process were repeated thread breakages, thread cluster formation at the opposite side of the embroidered patter, and non-precise positioning of the thread at different embroidery rounds. Further, during 3D printing, positioning of the starting point of the printing, resulting as misaligned 3D-printed layers, was a major challenge. This paper describes in detail the challenges encountered during the fabrication process of clothing-integrated basic wireless components, passive UHF RFID tags. Despite the introduced challenges, the ready-made textile-integrated tags showed excellent wireless performance and read ranges of around 6 meters.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: BioMediTech
Contributors: Khan, Z., He, H., Chen, X., Ukkonen, L., Virkki, J.
Number of pages: 6
Pages: 1372-1377
Publication date: 1 Jun 2019

Host publication information

Title of host publication: 2019 PhotonIcs and Electromagnetics Research Symposium - Spring, PIERS-Spring 2019 - Proceedings
Publisher: IEEE
Article number: 9017223
ISBN (Electronic): 9781728134031

Publication series

Name: Progress in Electromagnetics Research Symposium
Volume: 2019-June
ISSN (Print): 1559-9450
ISSN (Electronic): 1931-7360
ASJC Scopus subject areas: Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials
Source: Scopus
Source ID: 85082014277

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Embroidered and e-textile conductors embedded inside 3D-printed structures

This paper discusses the fabrication and wireless performance evaluation of textile-integrated passive ultra-high frequency (UHF) radiofrequency identification (RFID) tags, which are embedded inside flexible additively manufactured wireless platforms. Two different methods are utilized to fabricate the tag antenna, including embroidery with conductive thread and conductive e-textiles. After antenna fabrication, RFID ICs (integrated circuits) are attached to the antenna patterns, to achieve fully functional RFID tags. These two types of tags are embedded inside flexible 3D-printed platforms, which can protect the tags from mechanical stresses and moisture. Our preliminary results show that the peak read ranges of both types of platforms are higher than 6 meters, which are suitable for versatile wireless applications.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: BioMediTech
Contributors: Khan, Z., He, H., Chen, X., Ukkonen, L., Virkki, J.
Number of pages: 6
Pages: 1675-1680
Publication date: 1 Dec 2019

Host publication information

Title of host publication: 2019 Photonics and Electromagnetics Research Symposium - Fall, PIERS - Fall 2019 - Proceedings
Publisher: IEEE
Article number: 9021681
ISBN (Electronic): 9781728153049
ASJC Scopus subject areas: Electrical and Electronic Engineering, Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials, Mathematical Physics

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Electrical Contacts in SOI MEMS Using Aerosol Jet Printing

In this study, an additive method to make electrical contacts in SOI MEMS devices with aerosol jet printing is introduced. Small grooves were etched to the frame of MEMS accelerometer in the same step with the active structure release. Aluminum ink was jetted to the trenches in wafer-level to bridge the device layer to the handle wafer with the minimum amount of material. After subsequent annealing ohmic contacts between p-type device layer and p-type handle silicon were verified by I-V measurements. The via resistance less than 4 Y per via is measured. The method demonstrated in this work provides simple and low-cost approach for SOI handle contact where additional packaging of wafer process steps can be avoided.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Electronics and Communications Engineering, Research group: Laboratory for Future Electronics, Murata Electronics Oy
Contributors: Khorramdel, B., Torkkeli, A., Mäntysalo, M.
Pages: 34-40
Publication date: 2017
Peer-reviewed: Yes
Early online date: 19 Oct 2017

Publication information

Journal: IEEE Journal of the Electron Devices Society
Volume: 6
ISSN (Print): 2168-6734
Ratings: 
  • Scopus rating (2017): CiteScore 3.37 SJR 1.016 SNIP 1.465
Original language: English
ASJC Scopus subject areas: Biotechnology, Electronic, Optical and Magnetic Materials, Electrical and Electronic Engineering
Keywords: additive manufacturing., aerosol jet printing, Aerosols, Cavity resonators, Electrical resistance measurement, Ink, inkjet printing, microelectromechanical systems (MEMS), Micromechanical devices, Printing, silicon on insulator (SOI), Silicon-on-insulator
Source: Scopus
Source ID: 85032682442

Research output: Contribution to journalArticleScientificpeer-review

Accelerator-quality HTS dipole magnet demonstrator designs for the EuCARD-2 5-T 40-mm clear aperture magnet

Future high-energy accelerators will need very high magnetic fields in the range of 20 T. The Enhanced European Coordination for Accelerator Research and Development (EuCARD-2) Work Package 10 is a collaborative push to take high-temperature superconductor (HTS) materials into an accelerator-quality demonstrator magnet. The demonstrator will produce 5 T stand alone and between 17 and 20 T when inserted into the 100-mm aperture of a Fresca-2 high-field outsert magnet. The HTS magnet will demonstrate the field strength and the field quality that can be achieved. An effective quench detection and protection system will have to be developed to operate with the HTS superconducting materials. This paper presents a ReBCO magnet design using a multistrand Roebel cable that develops a stand-alone field of 5 T in a 40-mm clear aperture and discusses the challenges associated with a good field quality using this type of material. A selection of magnet designs is presented as the result of the first phase of development.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Electrical Engineering, Research area: Electromagnetics, Karlsruhe Institute of Technology, Insitute for Technical Physics, Germany, European Organization for Nuclear Research, French Atomic Energy Commission (CEA) Saclay, Physical Science Division (DSM), Institute of Research into the Fundamental Laws of the Universe (IRFU), Lawrence Berkeley National Laboratory, Karlsruhe Institute of Technology
Contributors: Kirby, G. A., Van Nugteren, J., Ballarino, A., Bottura, L., Chouika, N., Clement, S., Datskov, V., Fajardo, L., Fleiter, J., Gauthier, R., Gentini, L., Lambert, L., Lopes, M., Perez, J. C., De Rijk, G., Rijllart, A., Rossi, L., Ten Kate, H., Durante, M., Fazilleau, P., Lorin, C., Härö, E., Stenvall, A., Caspi, S., Marchevsky, M., Goldacker, W., Kario, A.
Publication date: 1 Jun 2015
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Applied Superconductivity
Volume: 25
Issue number: 3
Article number: 4000805
ISSN (Print): 1051-8223
Ratings: 
  • Scopus rating (2015): CiteScore 1.27 SJR 0.403 SNIP 1.046
Original language: English
ASJC Scopus subject areas: Electrical and Electronic Engineering, Condensed Matter Physics, Electronic, Optical and Magnetic Materials
Keywords: Accelerator magnet, EuCARD-2, HTS magnet design, quench protection, ReBCO, Superconducting Magnets, YBCO Roebel cable
Source: Scopus
Source ID: 84920829736

Research output: Contribution to journalArticleScientificpeer-review

Status of the Demonstrator Magnets for the EuCARD-2 Future Magnets Project

EuCARD-2 is a project partly supported by FP7 European Commission aiming at exploring accelerator magnet technology for 20-T dipole operating field. The EuCARD-2 collaboration is liaising with similar programs for high-field magnets in the U.S. and Japan. EuCARD-2 focuses, through the work package 10 'future magnets,' on the development of a 10-kA-class superconducting high-current-density cable suitable for accelerator magnets, for a 5-T stand-alone dipole of 40-mm bore and about 1-m length. After stand-alone testing, the magnet will be inserted in a large bore background dipole, 10-18 T. This paper reports on the design and development of models, which are called Feather0, wound with REBCO Roebel cable. Based on aligned block design to take advantage of the anisotropy of the REBCO tapes, Feather0 is a precursor of Feather2, which should reach the project goals in 2016. Feather0 is planned to be tested both in stand alone and as an insert mounted in the CERN Fresca facility providing 10-T background field. The progress of other designs pursued in the collaboration, one based on classical cos θ layout with Roebel cable and the other based on coil block with stacked tape cable, will be also reported.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Electrical Engineering, Research area: Electromagnetics, European Organization for Nuclear Research, Grenoble Institute of Technology, University of Twente, French Atomic Energy Commission (CEA) Saclay, Karlsruhe Institute of Technology, Insitute for Technical Physics, Germany, Universite de Geneve, Bruker HTS, Istituto Nazionale Di Fisica Nucleare, Frascati, University of Southampton, United Kingdom, Danish Institute of Technology
Contributors: Kirby, G., Rossi, L., Badel, A., Bajko, M., Ballarino, A., Bottura, L., Dhalle, M., Durante, M., Fazilleau, P., Fleiter, J., Goldacker, W., Härö, E., Himbele, J., Kario, A., Langeslag, S., Lorin, C., Murtzomaki, J., Van Nugteren, J., De Rijk, G., Salmi, T., Senatore, C., Stenvall, A., Tixador, P., Usoskin, A., Volpini, G., Yang, Y., Zangenberg, N.
Publication date: 1 Apr 2016
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Applied Superconductivity
Volume: 26
Issue number: 3
Article number: 4003307
ISSN (Print): 1051-8223
Ratings: 
  • Scopus rating (2016): CiteScore 1.42 SJR 0.398 SNIP 1.132
Original language: English
ASJC Scopus subject areas: Electrical and Electronic Engineering, Condensed Matter Physics, Electronic, Optical and Magnetic Materials
Keywords: Accelerators magnets, CLIQ, EuCARD-2, future magnets, higherature-superconductors, superconducting magnets
Source: Scopus
Source ID: 84963812427

Research output: Contribution to journalArticleScientificpeer-review

First Cold Powering Test of REBCO Roebel Wound Coil for the EuCARD2 Future Magnet Development Project

EuCARD-2 is a project partly supported by FP7-European Commission aiming at exploring accelerator magnet technology for 20 T dipole operating field. The EuCARD-2 collaboration is liaising with similar programs for high field magnets in the USA and Japan. EuCARD-2 focuses, through the work-package 10 'Future magnets,' on the development of a 10 kA-class superconducting, high current density cable suitable for accelerator magnets, for a 5 T stand-alone dipole of 40 mm bore and about 1 m length. After standalone testing, the magnet will possibly be inserted in a large bore background dipole, to be tested at a peak field up to 18 T. This paper starts by reporting on a few of the highlight simulations that demonstrate the progress made in predicting: dynamic current distribution and influence on field quality, complex quench propagation between tapes, and minimum quench energy in the multitape cable. The multiphysics output importantly helps predicting quench signals and guides the development of the novel early detection systems. Knowing current position within individual tapes of each cable we present stress distribution throughout the coils. We report on the development of the mechanical component and assembly processes selected for Feather-M2 the 5 T EuCARD2 magnet. We describe the CERN variable temperature flowing helium cold gas test system. We describe the parallel integration of the FPGA early quench detection system, using pickup coils and temperature sensors, alongside the standard CERN magnet quench detection system using voltage taps. Finally we report on the first cold tests of the REBCO 10 kA class Roebel subscale coil named Feather-M0.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Electrical Energy Engineering, Research group: Modelling and superconductivity, European Organization for Nuclear Research, IRFM, Karlsruhe Institute of Technology, Campus North, Bruker HTS
Contributors: Kirby, G. A., Van Nugteren, J., Bajas, H., Benda, V., Ballarino, A., Bajko, M., Bottura, L., Broekens, K., Canale, M., Chiuchiolo, A., Gentini, L., Peray, N., Perez, J. C., De Rijk, G., Rijllart, A., Rossi, L., Murtomaeki, J., Mazet, J., Pincot, F. O., Volpini, G., Durante, M., Fazilleau, P., Lorin, C., Stenvall, A., Goldacker, W., Kario, A., Usoskin, A.
Publication date: 1 Jun 2017
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Applied Superconductivity
Volume: 27
Issue number: 4
Article number: 4003307
ISSN (Print): 1051-8223
Ratings: 
  • Scopus rating (2017): CiteScore 1.45 SJR 0.408 SNIP 0.962
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Electrical and Electronic Engineering
Keywords: accelerators magnets, cryogenic systems, EuCARD-2, future magnets, high-temperature-superconductors, HTS, metal 3-D printing, Roebel cable, Superconducting magnets
Source: Scopus
Source ID: 85017652750

Research output: Contribution to journalArticleScientificpeer-review

Observation of PT-symmetric quantum interference

A common wisdom in quantum mechanics is that the Hamiltonian has to be Hermitian in order to ensure a real eigenvalue spectrum. Yet, parity–time (PT)-symmetric Hamiltonians are sufficient for real eigenvalues and therefore constitute a complex extension of quantum mechanics beyond the constraints of Hermiticity. However, as only single-particle or classical wave physics has been exploited so far, an experimental demonstration of the true quantum nature of PT symmetry has been elusive. In our work, we demonstrate two-particle quantum interference in a PT-symmetric system. We employ integrated photonic waveguides to reveal that the quantum dynamics of indistinguishable photons shows strongly counterintuitive features. To substantiate our experimental data, we analytically solve the quantum master equation using Lie algebra methods. The ideas and results presented here pave the way for non-local PT-symmetric quantum mechanics as a novel building block for future quantum devices.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Physics, Universität Rostock, Albert
Contributors: Klauck, F., Teuber, L., Ornigotti, M., Heinrich, M., Scheel, S., Szameit, A.
Publication date: 16 Sep 2019
Peer-reviewed: Yes

Publication information

Journal: Nature Photonics
ISSN (Print): 1749-4885
Ratings: 
  • Scopus rating (2019): SJR 13.614 SNIP 7.931