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 7.2 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

Walking anisotropic spatial solitons and their steering in nematic liquid crystals

A novel nematic liquid crystal cell allows the excitation of anisotropic spatial solitons and their angular steering, acting on walk-off thru the applied bias. The input interface enables polarization-healing soliton generation and spatial routing.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: University “Roma Tre”, Nonlinear Optics and OptoElectronics Lab, University of Calabria
Contributors: Peccianti, M., Alberucci, A., Assanto, G., De Luca, A., Coschignano, G., Umeton, C.
Publication date: 1 Jan 2005

Host publication information

Title of host publication: Nonlinear Guided Waves and Their Applications, NLGW 2005
Publisher: Optical Society of America OSA
ISBN (Print): 1557527911
ASJC Scopus subject areas: Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials, Electrical and Electronic Engineering

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 3.4 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

Very high dose electron irradiation effects on photoluminescence from GaInNAs/GaAs quantum wells grown by molecular beam epitaxy

The effects of 7 MeV electron irradiation at very high doses of 2×1017 and 1.5×1018electrons/cm2 and subsequent rapid thermal annealing on photoluminescence from a strain-compensated GaInAsN/GaAsN/GaAs quantum well structure are investigated. A large additional blueshift of photoluminescence has been observed from the lower-dose irradiated sample as compared to the non-irradiated one when annealed after the irradiation. This additional blueshift will become considerably reduced by an ageing effect, which occurs already at room temperature. The mechanism causing the additional blueshift of photoluminescence and its reduction is qualitatively assigned to metastable complex defects promoted by electron irradiation in the nitrogen containing layers. No such additional blueshift of photoluminescence under the thermal treatment has been observed in the higher-dose irradiated sample.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Photonics, National Institute for Research and Development in Microtechnologies Romania, Faculty of Exact Sciences and Engineering, Hyperion University
Contributors: Pavelescu, E. M., Bălţăţeanu, N., Spânulescu, S. I., Arola, E.
Number of pages: 5
Pages: 361-365
Publication date: 1 Feb 2017
Peer-reviewed: Yes

Publication information

Journal: Optical Materials
Volume: 64
ISSN (Print): 0925-3467
Ratings: 
  • Scopus rating (2017): CiteScore 3.7 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: Dilute nitrides, Electron irradiation, Photoluminescence

Bibliographical note

EXT="Pavelescu, E. M."

Source: Scopus
Source ID: 85008334984

Research output: Contribution to journalArticleScientificpeer-review

Utilizing triangular mesh with MMEV to study hysteresis losses of round superconductors obeying critical state model

Nature's minimum energy principle formulated in minimum magnetic energy variation (MMEV) and coupled with the Bean's critical state model (CSM) has resulted in feasible tools to model hysteresis losses in superconductors. These tools have been applied for single wires as well as for multi-turn coils in two-dimensional modelling domains. However, so far the discretization of the modelling domain has always relied on regular rectangular meshes. Therefore, the mesh representation of round filaments suffers from large discretization error if the mesh is not refined considerably more than triangular meshing would need. In this paper, we study the utilisation of triangular mesh in such a hysteresis loss modelling tool. We present the required extension to the already available knowledge that is needed to implement such a modelling tool. With our home-brewed tool, we study the convergence of the simulated transport current losses in the cross-section of a round wire represented with triangular and rectangular meshes of different types and of different densities. According to the results, triangular meshing is considerably more efficient than rectangular meshing for simulating transport current losses in the investigated situation.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Electrical Engineering, Research area: Electromagnetics
Contributors: Ruuskanen, J., Stenvall, A., Lahtinen, V.
Publication date: 1 Jun 2015
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Applied Superconductivity
Volume: 25
Issue number: 3
Article number: 8200405
ISSN (Print): 1051-8223
Ratings: 
  • Scopus rating (2015): CiteScore 2.5 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: critical state model, hysteresis losses, minimum magnetic energy variation, Numerical modelling
Source: Scopus
Source ID: 84921532493

Research output: Contribution to journalArticleScientificpeer-review

Unveiling and controlling the electronic structure of oxidized semiconductor surfaces: Crystalline oxidized InSb(100)(1 × 2)-O: Crystalline oxidized InSb(100)(1 × 2)-O

The exothermic nature of oxidation causes nearly all semiconductor applications in various fields like electronics, medicine, photonics, and sensor technology to acquire an oxidized semiconductor surface part during the application manufacturing. The significance of understanding and controlling the atomic scale properties of oxidized semiconductor surfaces is expected to increase even further with the development of nanoscale semiconductor crystals. The nature of oxidized semiconductor layers is, however, hard to predict and characterize as they are usually buried and amorphous. To shed light on these issues, we pursue a different approach based on oxidized III-V semiconductor layers that are crystalline. We present a comprehensive characterization of oxidized crystalline InSb(100)(1×2)-O layers by ab initio calculations, photoelectron spectroscopy, scanning tunneling microscopy, and spectroscopy, and demonstrate the electronic band structures of different oxidized phases of the semiconductor, which elucidate the previous contradictory semiconductor- oxidation effects. At 0.5 monolayer (ML) oxidation, oxygen atoms tend to occupy subsurface Sb sites, leading to metallic states in the semiconductor band gap, which arise from top dimers. When the oxidation is increased to the 1.0-2.0 ML concentration, oxygen occupies also interstitial sites, and the insulating band structure without gap states is stabilized with unusual occupied In dangling bonds. In contrast, the 2.5-3.0 ML oxide phases undergo significant changes toward a less ordered structure. The findings suggest a methodology for manipulating the electronic structure of oxidized semiconductor layers. © 2014 American Physical Society.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Optoelectronics Research Centre, Frontier Photonics, Turun Yliopisto/Turun Biomateriaalikeskus, Department of Physics and Astronomy, University of Turku, Lunds Universitet / Lunds Tekniska Högskola, Russian Academy of Sciences, Tampere University of Technology
Contributors: Lång, J. J. K., Punkkinen, M. P. J., Tuominen, M., Hedman, H. P., Vähä-Heikkilä, M., Polojärvi, V., Salmi, J., Korpijärvi, V. M., Schulte, K., Kuzmin, M., Punkkinen, R., Laukkanen, P., Guina, M., Kokko, K.
Number of pages: 9
Pages: 1-9
Publication date: 29 Jul 2014
Peer-reviewed: Yes

Publication information

Journal: Physical Review B
Volume: 90
Issue number: 4
Article number: 045312
ISSN (Print): 1098-0121
Ratings: 
  • Scopus rating (2014): CiteScore 7 SJR 2.762 SNIP 1.316
Original language: English
ASJC Scopus subject areas: Condensed Matter Physics, Electronic, Optical and Magnetic Materials

Bibliographical note

Contribution: organisation=orc,FACT1=1<br/>Portfolio EDEND: 2015-01-12<br/>Publisher name: American Physical Society

Source: researchoutputwizard
Source ID: 883

Research output: Contribution to journalArticleScientificpeer-review

Ultra-large mode area single frequency anisotropic MOPA with double clad Yb-doped tapered fiber

We demonstrates all-fiber master oscillator - power amplifier delivered 70W output power at 1033.33nm with 8 kHz FWHM linewidth without any problems with SBS. The anisotropic ytterbium doped tapered double clad amplifier with 50 μm MFD and polarization extinction ratio about 30 dB is developed as a burst stage. The output radiation demonstrated perfect beam quality (M2=1.03/1.08).

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Ampliconyx Ltd, Institute of Radio Engineering and Electronics of the Russian Academy of Sciences, St. Petersburg State Polytechnical University
Contributors: Noronen, T., Fedotov, A., Rissanen, J., Gumenyuk, R., Butov, O., Chamorovskii, Y., Golant, K., Odnoblyudov, M., Filippov, V.
Number of pages: 6
Publication date: 1 Jan 2018

Host publication information

Title of host publication: Fiber Lasers XV : Technology and Systems
Publisher: SPIE, IEEE
Article number: 105121T
ISBN (Electronic): 9781510615090

Publication series

Name: Proceedings of SPIE
Publisher: SPIE
Volume: 10512
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: active fiber, fiber amplifier, Fiber laser

Bibliographical note

EXT="Noronen, Teppo"
EXT="Fedotov, Andrei"
INT=fot, "Rissanen, Joona"
EXT="Gumenyuk, Regina"
EXT="Filippov, Valery"

Source: Scopus
Source ID: 85045656071

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

Ultrahigh-pressure form of Si O2 glass with dense pyrite-type crystalline homology

High-pressure synthesis of denser glass has been a longstanding interest in condensed-matter physics and materials science because of its potentially broad industrial application. Nevertheless, understanding its nature under extreme pressures has yet to be clarified due to experimental and theoretical challenges. Here we reveal the formation of OSi4 tetraclusters associated with that of SiO7 polyhedra in SiO2 glass under ultrahigh pressures to 200 gigapascal confirmed both experimentally and theoretically. Persistent homology analyses with molecular dynamics simulations found increased packing fraction of atoms whose topological diagram at ultrahigh pressures is similar to a pyrite-type crystalline phase, although the formation of tetraclusters is prohibited in the crystalline phase. This critical difference would be caused by the potential structural tolerance in the glass for distortion of oxygen clusters. Furthermore, an expanded electronic band gap demonstrates that chemical bonds survive at ultrahigh pressure. This opens up the synthesis of topologically disordered dense oxide glasses.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Physics, Research area: Computational Physics, Research group: Materials and Molecular Modeling, HCI e 486.1, Tohoku University, National Institute for Materials Science (NIMS), Japan Synchrotron Radiation Research Institute, Japan Advanced Institute of Science and Technology, Japan Science and Technology Agency, Tokyo University of Science, Norwegian Univ. of Sci. and Technol., University of Tokyo, Waseda University, National Institute of Advanced Industrial Science and Technology, Research and Services Division of Materials Data and Integrated System (MaDIS) NIMS, Kyoto Women's University, RIKEN Center for Integrative Medical Sciences, Aalto University, COMP Centre of Excellence, Department of Applied Physics, Aalto University, Division of Electrical Engineering and Computer Science, Kanazawa University
Contributors: Murakami, M., Kohara, S., Kitamura, N., Akola, J., Inoue, H., Hirata, A., Hiraoka, Y., Onodera, Y., Obayashi, I., Kalikka, J., Hirao, N., Musso, T., Foster, A. S., Idemoto, Y., Sakata, O., Ohishi, Y.
Publication date: 29 Jan 2019
Peer-reviewed: Yes

Publication information

Journal: Physical Review B
Volume: 99
Issue number: 4
Article number: 045153
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

Bibliographical note

EXT="Foster, A. S."

Source: Scopus
Source ID: 85060951368

Research output: Contribution to journalArticleScientificpeer-review

Ultrafast picosecond MOPA with Yb-doped tapered double clad fiber

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: Noronen, T., Gumenyuk, R., Chamorovskii, Y., Golant, K., Odnoblyudov, M., Filippov, V.
Publication date: 2017

Host publication information

Title of host publication: The European Conference on Lasers and Electro-Optics 2017 : Munich Germany 25–29 June 2017
Volume: Part F82-CLEO_Europe 2017
Publisher: The Optical Society; OSA
Article number: CJ_9_4
ISBN (Electronic): 978-1-5090-6736-7
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Mechanics of Materials
Source: Scopus
Source ID: 85039921118

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-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 3.4 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

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

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 11.9 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

Tuning electronic properties of graphene heterostructures by amorphous-to-crystalline phase transitions

The remarkable ability of phase change materials (PCM) to switch between amorphous and crystalline states on a nanosecond time scale could provide new opportunities for graphene engineering. We have used density functional calculations to investigate the structures and electronic properties of heterostructures of thin amorphous and crystalline films of the PCM GeTe (16 Å thick) and Ge2Sb2Te5 (20 Å) between graphene layers. The interaction between graphene and PCM is very weak, charge transfer is negligible, and the structures of the chalcogenide films differ little from those of bulk phases. A crystalline GeTe (111) layer induces a band gap opening of 80 meV at the Dirac point. This effect is absent for the amorphous film, but the Fermi energy shifts down along the Dirac cone by -60 meV. Ge2Sb2Te5 shows similar features, although inherent disorder in the crystalline rocksalt structure reduces the contrast in band structure from that in the amorphous structure. These features originate in charge polarization within the crystalline films, which show electromechanical response (piezoelectricity) upon compression, and show that the electronic properties of graphene structures can be tuned by inducing ultrafast structural transitions within the chalcogenide layers. Graphene can also be used to manipulate the structural state of the PCM layer and its electronic and optical properties.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Physics, Research area: Computational Physics, Research group: Materials and Molecular Modeling, COMP Centre of Excellence, Aalto University, Molecular Foundry, Lawrence Berkeley National Laboratory, Forschungszentrum Jülich (FZJ)
Contributors: Kulju, S., Akola, J., Prendergast, D., Jones, R. O.
Number of pages: 8
Publication date: 31 May 2016
Peer-reviewed: Yes

Publication information

Journal: Physical Review B
Volume: 93
Issue number: 19
Article number: 195443
ISSN (Print): 1098-0121
Ratings: 
  • Scopus rating (2016): CiteScore 8.6 SJR 2.339 SNIP 1.183
Original language: English
ASJC Scopus subject areas: Condensed Matter Physics, Electronic, Optical and Magnetic Materials
Source: Scopus
Source ID: 84973352747

Research output: Contribution to journalArticleScientificpeer-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

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

Transverse structure optimization of laterally-coupled ridge waveguide DFB lasers

A new figure of merit for single transverse mode operation and an accurate procedure for calculating the coupling coefficient in distributed feedback lasers with laterally-coupled ridge waveguide surface grating structures are introduced. Based on the difference in optical confinement between the pumped and un-pumped regions in the transverse plane, the single transverse mode figure of merit is effective and easy to calculate, while the improved coupling coefficient calculation procedure gives experimentally confirmed better results than the standard calculation approaches.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Optoelectronics Research Centre, Research group: Semiconductor Technology and Applications
Contributors: Uusitalo, T., Virtanen, H., Dumitrescu, M.
Number of pages: 2
Pages: 79-80
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
Article number: 7547038
ISBN (Electronic): 9781467386036
ASJC Scopus subject areas: Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Modelling and Simulation, Numerical Analysis
Source: Scopus
Source ID: 84987653468

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-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): CiteScore 13.8 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

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

Transmission, refraction, and focusing properties of labyrinth based left-handed metamaterials

In this present article, we studied the transmission, refraction and focusing properties of one, two and three dimensional labyrinth based left-handed metamaterials. We demonstrated that the proper periodic arrangement of labyrinth structures and wires results in left-handed transmission. By using a two dimensional labyrinth based left-handed slab, it is shown that it is possible to image the field emitted from source in sub-wavelength detail. Moreover, we demonstrated the focusing and negative refraction of electromagnetic waves by a three dimensional labyrinth based left-handed slab.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Nanotechnology Research Center
Contributors: Özbay, E., Bulu, I., Caglayan, H.
Number of pages: 9
Pages: 1202-1210
Publication date: Apr 2007
Peer-reviewed: Yes

Publication information

Journal: Physica Status Solidi (B) Basic Research
Volume: 244
Issue number: 4
ISSN (Print): 0370-1972
Ratings: 
  • Scopus rating (2007): SJR 0.871 SNIP 0.721
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics

Bibliographical note

EXT="Caglayan, Humeyra"

Source: Scopus
Source ID: 34247328206

Research output: Contribution to journalArticleScientificpeer-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 7.9 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

Towards REBCO 20T+ Dipoles for Accelerators

ReBCO High Temperature Superconducting (HTS) coated conductor tapes are a promising candidate for pushing the magnetic fields in accelerator magnets well beyond 20 T. They are capable of very high current densities in intense applied magnetic field, have a very high thermal stability, can withstand high transverse pressures and allow operation in 20 to 30 K helium gas flow, potentially reducing operating cost significantly. During the EuCARD2 program significant developments have been made in terms of coil design, manufacturing and testing. Now that EuCARD2 has come to an end, CERN and collaborators are initiating a new program to continue the development of HTS accelerator magnets. This paper presents our initial thoughts on the conceptual design of a 20 T+ accelerator magnet, using the results and technologies from EuCARD2 combined with some new ideas. The paper discusses the options available for the cross-sectional layout, the use of a hybrid configurations including Aligned Block, the design of the coil-ends and dual aperture configurations. Also discussed is the quench protection of the magnets. Due to the high thermal stability of the conductor and high energy densities it will be required to explore an entirely new approach.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Electrical Energy Engineering, European Organization for Nuclear Research
Contributors: van Nugteren, J., Kirby, G., Murtomaki, J., DeRijk, G., Rossi, L., Stenvall, A.
Publication date: Jun 2018
Peer-reviewed: Yes
Early online date: 27 Mar 2018

Publication information

Journal: IEEE Transactions on Applied Superconductivity
Volume: 28
Issue number: 4
Article number:  4008509
ISSN (Print): 1051-8223
Ratings: 
  • Scopus rating (2018): CiteScore 2.9 SJR 0.406 SNIP 0.987
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Electrical and Electronic Engineering
Keywords: Accelerator Dipoles, Accelerator magnets, Conductors, Current density, High-temperature superconductors, HTS Magnets, Magnet Stability, Magnet Structure, Perpendicular magnetic anisotropy, Quench Protection, Superconducting magnets
Source: Scopus
Source ID: 85044849023

Research output: Contribution to journalArticleScientificpeer-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

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 3.5 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

Three-color vector nematicon

Light localization via reorientation in nematic liquid crystals supports multi-component optical spatial solitons, i.e., vector nematicons. By launching three optical beams of different wavelengths and the same input polarization in a bias-free planar cell, we demonstrate a three-color vector nematicon which is self-trapped thanks to its incoherent nature.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Photonics, Politechnika Warszawska, Univ Roma Tre, Roma Tre University, Dept Elect Engn, NooEL, University “Roma Tre”, Aerosol Physics Laboratory
Contributors: Laudyn, U. A., Kwaśny, M., Karpierz, M. A., Assanto, G.
Number of pages: 3
Pages: 36-38
Publication date: 2017
Peer-reviewed: Yes

Publication information

Journal: Photonics Letters of Poland
Volume: 9
Issue number: 2
ISSN (Print): 2080-2242
Ratings: 
  • Scopus rating (2017): CiteScore 0.9 SJR 0.25 SNIP 0.446
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials
Electronic versions: 
Source: Scopus
Source ID: 85021814168

Research output: Contribution to journalArticleScientificpeer-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 0.7 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

Thickness variation study of RFID-based folded patch antennas for strain sensing

This paper explores folded patch antennas for the development of low-cost and wireless smart-skin sensors that monitor the strain in metallic structures. When the patch antenna is under strain/deformation, its resonance frequency varies accordingly. The variation can be easily interrogated and recorded by a wireless reader that also provides power for the antenna operation. The patch antenna adopts a specially selected substrate material with low dielectric constant, as well as an inexpensive off-the-shelf radiofrequency identification (RFID) chip for signal modulation. A thicker substrate increases RFID signal-to-noise ratio, but reduces the strain transfer efficiency. To experimentally study the effect of substrate thickness, two prototype folded patch antennas with different substrate thicknesses have been designed and manufactured. For both prototypes, tensile testing results show strong linearity between the interrogated resonance frequency and the strain experienced by the antenna. Longer interrogation range is achieved with the larger substrate thickness.

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
Contributors: Yi, X., Wu, T., Lantz, G., Wang, Y., Leon, R. T., Tentzeris, M. M.
Publication date: 2011

Host publication information

Title of host publication: Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2011
Volume: 7981
Article number: 79811H
ISBN (Print): 9780819485434
ASJC Scopus subject areas: Applied Mathematics, Computer Science Applications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Keywords: folded patch antenna, passive wireless sensor, RFID, strain sensor, substrate thickness
Source: Scopus
Source ID: 79956325124

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-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 6.1 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

Thermal, structural and optical properties of Er3+ doped phosphate glasses containing silver nanoparticles

The melt-quenching method is employed to prepare the amorphous phosphate glasses containing silver nanoparticles (Ag NPs). The structural characteristics of phosphate glasses were investigated by X-ray diffraction, thermal analysis, transmission electron microscopy, UV-Vis spectroscopy, Raman, and infrared spectroscopy. The transmission electron microscopic images confirm the presence of spherical silver NPs having an average diameter in the range of 20-40 nm. The EDX analysis spectrum shows the presence of Ag element. Important structural changes induced by the Ag2CO3 addition to the phosphate glass, Raman- and IR-spectroscopic studies were carried out in order to correlate the variations in the glass properties with variations of the glass structure. The surface plasmon resonance (SPR) peak of silver nanoparticles embedded in Er3 + doped phosphate glass is evidenced at ∼403 nm. From the absorption spectra, the optical band gap is found to decrease with the increase of Ag NPs' concentration. All the obtained results in the present study were reported and discussed in detail.

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, Physical Chemistry Laboratory of Mineral Materials and Their Applications, National Center of Research in Materials Science, Åbo Akademi
Contributors: Soltani, I., Hraiech, S., Horchani-Naifer, K., Massera, J., Petit, L., Férid, M.
Number of pages: 7
Pages: 67-73
Publication date: 15 Apr 2016
Peer-reviewed: Yes

Publication information

Journal: Journal of Non-Crystalline Solids
Volume: 438
ISSN (Print): 0022-3093
Ratings: 
  • Scopus rating (2016): CiteScore 3.5 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: FTIR and Raman spectra, Phosphate glasses, Silver nanoparticles (Ag NPs), Thermal stability

Bibliographical note

EXT="Petit, L."

Source: Scopus
Source ID: 84960866255

Research output: Contribution to journalArticleScientificpeer-review

Thermally evaporated single-crystal Germanium on Silicon

Using conventional and polarization-dependent Raman spectroscopy we investigate the structural properties of Germanium films thermally evaporated on Silicon under various conditions. The analysis suggests that the Ge films can be crystalline, amorphous and poly-oriented, depending on the substrate temperature. We use both comparison with Raman spectra of Ge films grown on amorphous substrates and polarization-dependent Raman measurements to demonstrate that in the 250-450 °C interval, crystalline Ge films are epitaxial. This result is validated by means of large angle X-ray diffraction measurements. We employ these films to fabricate and characterize near infrared heterojunction photodiodes that exhibit high responsivities and low dark current densities.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Frontier Photonics, University “Roma Tre”, Università dell'Aquila, Nonlinear Optics and OptoElectronics Lab
Contributors: Sorianello, V., Colace, L., Nardone, M., Assanto, G.
Number of pages: 4
Pages: 8037-8040
Publication date: 1 Sep 2011
Peer-reviewed: Yes

Publication information

Journal: Thin Solid Films
Volume: 519
Issue number: 22
ISSN (Print): 0040-6090
Ratings: 
  • Scopus rating (2011): CiteScore 3.4 SJR 0.995 SNIP 1.323
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: Germanium, Near infrared, Photodetectors, Raman characterization, Thermal evaporation
Source: Scopus
Source ID: 80052110605

Research output: Contribution to journalArticleScientificpeer-review

Thermal evaporation of Ge on Si for near infrared detectors: Material and device characterization

Using a low-temperature process, we thermally evaporated Ge thin films on Si substrates and investigated both structural and electrical properties of samples grown at various temperatures. The characterization included X-ray diffraction, atomic force microscopy and Hall measurements and aimed at determining a suitable temperature range in terms of crystal quality and transport properties. Finally, we employed Ge films on Si to fabricate near infrared photodiodes and test them in terms of dark current and responsivity.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Frontier Photonics, University “Roma Tre”, Nonlinear Optics and OptoElectronics Lab, Centro S3, Institute IMEM-CNR
Contributors: Sorianello, V., Colace, L., Assanto, G., Notargiacomo, A., Armani, N., Rossi, F., Ferrari, C.
Number of pages: 4
Pages: 526-529
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 2.8 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, Photodetectors, Thermal evaporation
Source: Scopus
Source ID: 79751530052

Research output: Contribution to journalArticleScientificpeer-review

Thermal effects on the Wigner localization and Friedel oscillations in many-electron nanowires

Thermal effects on the total charge density are studied for a one-dimensional correlated quantum dot by means of the path integral Monte Carlo method. The competition between Friedel and Wigner oscillations at zero temperature is driven by the ratio between the interaction of electronic strength and the kinetic energy of electrons. At the onset of the formation of a Wigner molecule, we show that thermal enhancement of Wigner oscillations occurs in a range of temperatures, which can be observed in the electron density. We further show that low-temperature Friedel oscillations may change to Wigner oscillations upon an increase in the temperature.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Physics, CNR-SPIN, University of Würzburg
Contributors: Kylänpää, I., Cavaliere, F., Ziani, N. T., Sassetti, M., Räsänen, E.
Publication date: 13 Sep 2016
Peer-reviewed: Yes

Publication information

Journal: Physical Review B
Volume: 94
Issue number: 11
Article number: 115417
ISSN (Print): 1098-0121
Ratings: 
  • Scopus rating (2016): CiteScore 8.6 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: 84990960683

Research output: Contribution to journalArticleScientificpeer-review

Thermal effects on a passive wireless antenna sensor for strain and crack sensing

For application in structural health monitoring, a folded patch antenna has been previously designed as a wireless sensor that monitors strain and crack in metallic structures. Resonance frequency of the RFID patch antenna is closely related with its dimension. To measure stress concentration in a base structure, the sensor is bonded to the structure like a traditional strain gage. When the antenna sensor is under strain/deformation together with the base structure, the antenna resonance frequency varies accordingly. The strain-related resonance frequency variation is wirelessly interrogated and recorded by a reader, and can be used to derive strain/deformation. Material properties of the antenna components can have significant effects on sensor performance. This paper investigates thermal effects through both numerical simulation and temperature chamber testing. When temperature fluctuates, previous sensor design (with a glass microfiber-reinforced PTFE substrate) shows relatively large variation in resonance frequency. To improve sensor performance, a new ceramic-filled PTFE substrate material is chosen for re-designing the antenna sensor. Temperature chamber experiments are also conducted to the sensor with new substrate material, and compared with previous design.

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: Yi, X., Vyas, R., Cho, C., Fang, C. H., Cooper, J., Wang, Y., Leon, R. T., Tentzeris, M. M.
Publication date: 2012

Host publication information

Title of host publication: Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2012
Volume: 8345
Article number: 83450F
ISBN (Print): 9780819490025
ASJC Scopus subject areas: Applied Mathematics, Computer Science Applications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Keywords: Crack sensor, Folded patch antenna, Passive wireless sensor, RFID, Strain sensor, Thermal effect
Source: Scopus
Source ID: 84861112128

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-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 3.7 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

Theoretical studies of structural properties of the high-Tc superconductor Y1Ba2Cu3O7-x

Structural properties of the high temperature oxide superconductor Y1Ba2Cu3O7-gc have been studied by static lattice simulation methods. Empirical (ionic) potentials, derived on the basis of experimental data, are used to describe the basic structural properties of the superconductive oxides. Several potential models, with different location of the extra charge for the O7 compound, have been tested with respect to experimental lattice parameters. Fair parametrizations have been found in almost all cases, but they are usually valid only for a specific oxygen content. However, potential models, consistent both for O6 and O7, have been found. We present the best of our ionic models, where, in O7, two thirds of the holes are distributed in the sheet-site oxygens and one third in oxygens between the sheet and chain planes.

General information

Publication status: Published
MoE publication type: Not Eligible
Organisations: Brookhaven National Laboratory
Contributors: Valkealahti, S., Welch, D. O.
Number of pages: 2
Pages: 540-541
Publication date: 1 Jan 1989
Peer-reviewed: Yes

Publication information

Journal: Physica C: Superconductivity and its Applications
Volume: 162-164
Issue number: PART 1
ISSN (Print): 0921-4534
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Energy Engineering and Power Technology, Electrical and Electronic Engineering
Source: Scopus
Source ID: 0024887115

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

The Impact of Protection Heater Delays Distribution on the Hotspot Temperature in a High-Field Accelerator Magnet

Quench protection is one of the challenges in the development of high-field superconducting magnets for future particle accelerators, such as the High-Energy and High-Luminosity LHC. The protection of the accelerator magnets up to now has relied on protection heaters to spread the normal zone across the winding, thus increasing the magnet resistance. The design of the protection heaters layout largely deals with the optimal positioning of the available heater energy on the coil surface. The aim is to quickly bring a large fraction of the winding to resistive state and induce a fast current discharge. Since the coil consists of different field regions, different approaches for heater energy distribution can be considered. Possible optimization criteria can be, for example, the minimum average delay in all the coils, the minimum first delay, or the minimum last delay. In this paper, we present a study of the impact of heater delay distribution on the resulting current decay and hotspot temperature. We use our newly developed current decay model to simulate the magnet current decay rate for different heater designs. We consider the case of the LARP-CERN MQXF magnet, being developed for the LHC luminosity upgrade.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Electrical Engineering, Research area: Electromagnetics
Contributors: Salmi, T., Stenvall, A.
Publication date: 1 Jun 2016
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Applied Superconductivity
Volume: 26
Issue number: 4
Article number: 4001405
ISSN (Print): 1051-8223
Ratings: 
  • Scopus rating (2016): CiteScore 2.6 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: Heater delays, hotspot temperature, protection heaters, quench protection, superconductingmagnets
Source: Scopus
Source ID: 84962385287

Research output: Contribution to journalArticleScientificpeer-review

The EuCARD2 Future Magnets Program for particle accelerator high field dipoles: review of results and next steps

The EuCARD2 collaboration aims at the development of a 10 kA-class superconducting, high current density cable suitable for accelerator magnets, to be tested in small coils and magnets capable to deliver 3-5 T when energized in stand-alone mode, and 15-18 T when inserted in a 12-13 T background magnet. REBCO tape, assembled in a Roebel cable, was selected as conductor. The developed REBCO tape has reached a record engineering critical current density, at 4.2 K and 18 T of 956 A/mm2. Roebel cable carried up to 13 kA at 20K when tested in a small coil (FeatherM0.4). Then a first dipole magnet, wound with two low grade Roebel cables of 25 m each, was assembled and tested. The dipole reached the short sample critical current of 6 kA generating more than 3 T central field at about 5.7 K, with indications of good current transfer among cable strands and of relatively soft transition. The construction of a costheta dipole is also discussed. Eucard2 is reaching its objective and is continuing with the H2020-ARIES program aiming at doubling the Je at 20 T to obtain 6 T as standalone and 18 T as insert in a high field facility.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Electrical Energy Engineering, European Organization for Nuclear Research, CNRS Centre National de la Recherche Scientifique, Universite de Geneve, Istituto Nazionale Di Fisica Nucleare, Frascati, University of Twente, IRFM, Institut de Recherche sur les Lois Fondamentales de l'Univers, Karlsruhe Institute of Technology, Insitute for Technical Physics, Germany, Karlsruhe Institute for Technology, Geneva University Hospital, Institut NÉEL, University of Southampton, United Kingdom, Danish Technological Institute
Contributors: Rossi, L., Badel, A., Bajas, H., Bajko, M., Ballarino, A., Barth, C., Betz, U., Bottura, L., Broggi, F., Chiuchiolo, A., Dhalle, M., Durante, M., Fazilleau, P., Fleiter, J., Gao, P., Goldacker, W., Kario, A., Kirby, G., Lorin, C., Murtomaeki, J. S., van Nugteren, J., Petrone, C., DeRijk, G., Senatore, C., Statera, M., Stenvall, A., Tixador, P., Yang, Y., Usoskin, A., Zangenberg, N.
Publication date: Apr 2018
Peer-reviewed: Yes
Early online date: 22 Dec 2017

Publication information

Journal: IEEE Transactions on Applied Superconductivity
Volume: 28
Issue number: 3
ISSN (Print): 1051-8223
Ratings: 
  • Scopus rating (2018): CiteScore 2.9 SJR 0.406 SNIP 0.987
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Electrical and Electronic Engineering
Keywords: Accelerator Magnets, Coils, Collaboration, Conductors, Critical current density (superconductivity), High-temperature superconductors, HTS conductor, HTS dipoles, Superconducting magnets
Source: Scopus
Source ID: 85039777831

Research output: Contribution to journalArticleScientificpeer-review

The EuCARD-2 future magnets European collaboration for accelerator-quality HTS magnets

EuCARD-2 is a project supported by FP7-European Commission that includes, inter alia, a work-package (WP10) called "Future Magnets." This project is part of the long term development that CERN is launching to explore magnet technology at 16 T to 20 T dipole operating field, within the scope of a study on Future Circular Colliders. The EuCARD2 collaboration is closely liaising with similar programs for high field accelerator magnets in the USA and Japan. The main focus of EuCARD2 WP10 is the development of a 10 kA-class superconducting, high current density cable suitable for accelerator magnets, The cable will be used to wind a stand-alone magnet 500 mm long and with an aperture of 40 mm. This magnet should yield 5 T, when stand-alone, and will enable to reach a 15 to 18 T dipole field by placing it in a large bore background dipole of 12-15 T. REBCO based Roebel cables is the baseline. Various magnet configurations with HTS tapes are under investigation and also use of Bi-2212 round wire based cables is considered. The paper presents the structure of the collaboration and describes the main choices made in the first year of the program, which has a breadth of five to six years of which four are covered by the FP7 frame.

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, University of Southampton, Istituto Nazionale Di Fisica Nucleare, Frascati, CERN, Conseil Europeen pour la Recherche Nucleaire, Accelerator and Technology Sector, Institut Polytechnique de Grenoble, University of Twente, CEA, Institute of Research into the Fundamental Laws of the Universe (IRFU), Karlsruhe Institute of Technology, Departement de Physique de la Matiere Condensee (DPMC), University of Geneva, Bruker HTS GmbH, Istituto Nazionale di Fisica Nucleare (INFN), Laboratorio Acceleratori e Superconduttivita Applicata (LASA), Danish Institute of Technology
Contributors: Rossi, L., Badel, A., Bajko, M., Ballarino, A., Bottura, L., Dhallé, M. M. J., Durante, M., Fazilleau, P., Fleiter, J., Goldacker, W., Härö, E., Kario, A., Kirby, G., Lorin, C., 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 Jun 2015
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Applied Superconductivity
Volume: 25
Issue number: 3
Article number: 4001007
ISSN (Print): 1051-8223
Ratings: 
  • Scopus rating (2015): CiteScore 2.5 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: Accelerators Magnets, Eucard2, Future Magnets, High-temperature superconductors, Superconducting Magnets
Source: Scopus
Source ID: 84920911143

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 5.2 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

The effects of I/Q imbalance on wireless communications: A survey

Radio frequency front-ends constitute a core part of both conventional and emerging communication systems. Yet, although hardware realizations practically suffer from several types of impairments that degrade the overall system performance, the corresponding effects are often neglected and transceivers are assumed ideal. This typically refers to effects that are typically related to amplier nonlinearities, phase noise and in phase and quadrature imbalance (IQI), with the latter being among the most critical ones. In this context, this work provides a thorough survey on the effects of IQI, aiming to highlight their important manifestations which depending on the considered scenario can result to destructive and occasionally constructive effects.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Electronics and Communications Engineering, Research group: Wireless Communications and Positioning, Khalifa University, Department of Electrical and Computer Engineering, University of Surrey, Aristotle University of Thessaloniki
Contributors: Selim, B., Sofotasios, P. C., Muhaidat, S., Karagiannidis, G. K.
Publication date: 2 Mar 2017

Host publication information

Title of host publication: 2016 IEEE 59th International Midwest Symposium on Circuits and Systems (MWSCAS)
Publisher: IEEE
ISBN (Electronic): 9781509009169
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Electrical and Electronic Engineering

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 5.2 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

The 16 T Dipole Development Program for FCC

A key challenge for a future circular collider (FCC) with centre-of-mass energy of 100 TeV and a circumference in the range of 100 km is the development of high-field superconducting accelerator magnets, capable of providing a 16 T dipolar field of accelerator quality in a 50 mm aperture. This paper summarizes the strategy and actions being undertaken in the framework of the FCC 16 T Magnet Technology Program and the Work Package 5 of the EuroCirCol.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Electrical Energy Engineering, Research area: Power engineering, Research group: Modelling and superconductivity, European Organization for Nuclear Research, Istituto Nazionale Di Fisica Nucleare, Frascati, University of Twente, French Atomic Energy Commission (CEA) Saclay, Environment and Technology, KEK, Universite de Geneve
Contributors: Tommasini, D., Auchmann, B., Bajas, H., Bajko, M., Ballarino, A., Bellomo, G., Benedikt, M., Bermudez, S. I., Bordini, B., Bottura, L., Buzio, M., Dhalle, M., Durante, M., De Rijk, G., Fabbricatore, P., Farinon, S., Ferracin, P., Gao, P., Lackner, F., Lorin, C., Marinozzi, V., Martinez, T., Munilla, J., Ogitsu, T., Ortwein, R., Perez, J., Prioli, M., Rifflet, J. M., Rochepault, E., Russenschuck, S., Salmi, T., Savary, F., Schoerling, D., Segreti, M., Senatore, C., Sorbi, M., Stenvall, A., Todesco, E., Toral, F., Verweij, A. P., Volpini, G., Wessel, S., Wolf, F.
Publication date: 1 Jun 2017
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Applied Superconductivity
Volume: 27
Issue number: 4
Article number: 4000405
ISSN (Print): 1051-8223
Ratings: 
  • Scopus rating (2017): CiteScore 2.7 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: 16 T, FCC, NbSn, superconducting
Source: Scopus
Source ID: 85012994421

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 2.6 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

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 2.5 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

Temporal ghost imaging using wavelength conversion and two-color detection

Ghost imaging constructs an image by correlating two signals: one that interacts with an object but possesses no spatial information, and the other that contains spatial information but does not interact with the object. Ghost imaging can be extended into the time domain by using laser intensity fluctuations to reconstruct an unknown time-varying pattern, but this requires the measurement of laser fluctuations on ultrafast timescales, a significant limitation at wavelengths where ultrafast detectors are not available.We overcome this by using wavelength conversion to shift the probe laser into a spectral region where ultrafast detectors are available, and we apply this technique to image a temporal object at 2 μm. Our results demonstrate that temporal correlation information can be transferred to an arbitrary spectral region, opening possibilities for ultrafast ghost imaging at new wavelengths.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Physics, University of Electronic Science and Technology of China, UMR 6174, Ita-Suomen yliopisto
Contributors: Wu, H., Ryczkowski, P., Friberg, A. T., Dudley, J. M., Genty, G.
Number of pages: 5
Pages: 902-906
Publication date: 20 Jul 2019
Peer-reviewed: Yes

Publication information

Journal: Optica
Volume: 6
Issue number: 7
ISSN (Print): 2334-2536
Ratings: 
  • Scopus rating (2019): CiteScore 18.1 SJR 5.6 SNIP 3.375
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Atomic and Molecular Physics, and Optics

Bibliographical note

INT=phys,"Wu, Han"

Source: Scopus
Source ID: 85071154886

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

Tailoring directional scattering of second-harmonic generation from (111)-GaAs nanoantennas

The group of zincblende III-V compound semiconductors, especially (100)-grown AlGaAs and GaAs, have recently been presented as promising materials for second harmonic generation (SHG) at the nanoscale. However, major obstacles to push the technology towards practical applications are the limited control over directionality of the SH emission and especially zero forward/backward radiation. In this work we provide both theoretically and experimentally a solution to these problems by presenting the first SHG nanoantennas made from (111)-GaAs embedded in a low index material. These nanoantennas show superior forward directionality compared to their (100)-counterparts. Most importantly, it is possible to manipulate the SHG radiation pattern of the nanoantennas by changing the pump polarization without affecting the linear properties and the total nonlinear conversion efficiency.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Research group: Nonlinear Optics, Physics, Australian National University, Friedrich-Schiller-University Jena, School of Engineering and Information Technology, University of New South Wales (UNSW) Australia, Institute of Applied Physics of the Russian Academy of Sciences
Contributors: Sautter, J., Xu, L., Miroshnichenko, A., Lysevych, M., Volkovskaya, I., Smirnova, D., Camacho Morales, M., Zangeneh Kamali, K., Karouta, F., Vora, K., Tan, H. H., Kauranen, M., Staude, I., Jagadish, C., Neshev, D. N., Rahmani, M.
Publication date: 2019

Host publication information

Title of host publication: AOS Australian Conference on Optical Fibre Technology, ACOFT 2019 and Australian Conference on Optics, Lasers, and Spectroscopy, ACOLS 2019
Publisher: SPIE
Editors: Mitchell, A., Rubinsztein-Dunlop, H.
Article number: 112000H
ISBN (Electronic): 9781510631403

Publication series

Name: Proceedings of SPIE - The International Society for Optical Engineering
Volume: 11200
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: Dielectric nanoantennas, Directional emission, Multipolar interference, Second harmonic generation

Bibliographical note

jufoid=71479

Source: Scopus
Source ID: 85079653740

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

System-level design for partially reconfigurable hardware

In this paper, we present a SystemC-based approach for system-level design of partially reconfigurable hardware. The main focuses are resource estimation to support system analysis, reconfiguration modeling for fast performance simulation, automatic generation of reconfigurable components and a static prefetch scheduler. The approach was applied in a real design case of a part of a WCDMA decoding algorithm on a commercial reconfigurable platform.

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, Digitaali- ja tietokonetekniikka, VTT Technical Research Centre of Finland
Contributors: Qu, Y., Tiensyrjä, K., Soininen, J. P., Nurmi, J.
Number of pages: 4
Pages: 2738-2741
Publication date: 2007

Host publication information

Title of host publication: 2007 IEEE International Symposium on Circuits and Systems
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Electrical and Electronic Engineering
Source: Scopus
Source ID: 34548825693

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

Symmetry-broken electronic structure and uniaxial Fermi surface nesting of untwinned CaFe 2 As 2

We used angle-resolved photoemission spectroscopy to make direct measurements of the electronic structure of the untwinned uniaxial state of CaFe2As2, the parent compound of an iron-based superconductor. The very small photon beam size, combined with the relatively large single-domain area on the crystal surfaces, allowed us to obtain the intrinsic symmetry-broken dispersions and Fermi surface (FS) geometries along the orthogonal Fe-Fe bond directions without any mechanical or magnetic detwinning processes. Comparing the optimized local density approximation calculations, an orbital-dependent band shifting is introduced to obtain better agreement, which is consistent with the development of orbital ordering. More interestingly, unidirectional straight and flat FS segments are observed near the zone center, which indicates the existence of a unidirectional charge density wave order. Our results indicate strong electronic anisotropy in CaFe2As2 and put strong constraints on theories for the iron-pnictide system.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Computational Science X (CompX), Los Alamos National Laboratory, University of Science and Technology of China, Lawrence Berkeley National Laboratory, Northeastern University, University of Colorado at Boulder
Contributors: Wang, Q., Sun, Z., Rotenberg, E., Ronning, F., Bauer, E. D., Lin, H., Markiewicz, R. S., Lindroos, M., Barbiellini, B., Bansil, A., Dessau, D. S.
Publication date: 26 Dec 2013
Peer-reviewed: Yes

Publication information

Journal: Physical Review B
Volume: 88
Issue number: 23
Article number: 235125
ISSN (Print): 1098-0121
Ratings: 
  • Scopus rating (2013): CiteScore 6.9 SJR 2.813 SNIP 1.32
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Source: Scopus
Source ID: 84892419860

Research output: Contribution to journalArticleScientificpeer-review

Switchable unidirectional second-harmonic emission through GaAs nanoantennas

Switching the scattering direction of high-index dielectric nanoantennas between forward and backward, via Mie resonances in the linear regime, has been widely studied, recently. However, switching the harmonic emission of nanoantennas without applying any physical change to the antennas, such as geometry, or environment, is a chal-lenging task that has not been demonstrated yet. Here, we investigate multipolar second-harmonic switch from GaAs nanoantennas. Based on the peculiar nonlinearities of zinc-blende semiconductors, we demonstrate both theoretically and experimentally unidirectional nonlinear emission routing and switching via pump polarization control. Our results offer exciting opportunities for nonlinear nanophotonics technologies, such as nanoscale light routing elements, nonlinear light sources, nonlinear imaging, multifunctional flat optical elements.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Research group: Nonlinear Optics, Physics, School of Engineering and Information Technology, University of New South Wales (UNSW) Australia, HCI e 486.1, Australian National University, Institute of Applied Physics of the Russian Academy of Sciences
Contributors: Xu, L., Saerens, G., Timofeeva, M., Miroshnichenko, A. E., Camacho-Morales, R., Volkovskaya, I., Smirnova, D. A., Lysevych, M., Huang, L., Cai, M., Karouta, F., Hoe Tan, H., Kauranen, M., Jagadish, C., Grange, R., Neshev, D. N., Rahmani, M.
Publication date: 2019

Host publication information

Title of host publication: AOS Australian Conference on Optical Fibre Technology, ACOFT 2019 and Australian Conference on Optics, Lasers, and Spectroscopy, ACOLS 2019
Publisher: SPIE
Editors: Mitchell, A., Rubinsztein-Dunlop, H.
Article number: 112000J
ISBN (Electronic): 9781510631403

Publication series

Name: Proceedings of SPIE - The International Society for Optical Engineering
Volume: 11200
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: Dielectric nanoresonators, Mie resonance, Second harmonic generation, Unidirectional emission

Bibliographical note

jufoid=71479

Source: Scopus
Source ID: 85079683447

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

Surface-relief gratings and stable birefringence inscribed using light of broad spectral range in supramolecular polymer-bisazobenzene complexes

We report on phenol-pyridine hydrogen-bonded supramolecular polymer-azobenzene complexes made from a newly designed polar bisazobenzene chromophore. Because of the substitution with a polar nitro group, the chromophore possesses an extremely broad absorption band, spanning from near-UV up to 650 nm. Moreover, the inclusion of two methoxy groups to the central benzene ring prevents excessive chromophore-chromophore intermolecular interactions and provides advantageous size-related properties. Together, these features of the prepared photoresponsive polymer materials enable efficient inscription of (i) photoinduced birefringence with outstanding stability at various chromophore concentrations and (ii) surface-relief grating formation over a wide range of writing wavelengths from 405 to 633 nm. The photoresponsive behavior is compared to that of Disperse Yellow 7-based supramolecular complexes.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Frontier Photonics, Department of Applied Physics, Aalto University, Tokyo Institute of Technology, University of Bristol
Contributors: Koskela, J. E., Vapaavuori, J., Hautala, J., Priimagi, A., Faul, C. F. J., Kaivola, M., Ras, R. H. A.
Number of pages: 8
Pages: 2363-2370
Publication date: 26 Jan 2012
Peer-reviewed: Yes

Publication information

Journal: Journal of Physical Chemistry C
Volume: 116
Issue number: 3
ISSN (Print): 1932-7447
Ratings: 
  • Scopus rating (2012): CiteScore 8 SJR 2.529 SNIP 1.461
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: 84856360260

Research output: Contribution to journalArticleScientificpeer-review

Surface-induced charge state conversion of nitrogen-vacancy defects in nanodiamonds

We present a study of the charge state conversion of single nitrogen-vacancy (NV) defects hosted in nanodiamonds (NDs). We first show that the proportion of negatively charged NV- defects, with respect to its neutral counterpart NV0, decreases with the size of the ND. We then propose a simple model based on a layer of electron traps located at the ND surface which is in good agreement with the recorded statistics. By using thermal oxidation to remove the shell of amorphous carbon around the NDs, we demonstrate a significant increase in the proportion of NV- defects in 10 nm NDs. These results are invaluable for further understanding, control, and use of the unique properties of negatively charged NV defects in diamond.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Ecole Polytechnique de Montreal, Canada, Laboratoire de Photonique Quantique et Moléculaire-ENS Cachan, Laboratoire de Physique de la Matière Condensée-Ecole Polytechnique-CNRS, CEA/CNG, UMR CNRS 8537, UMR CNRS 7643, Ecole Polytechnique, LIST, Diamond Sensors Laboratory, Laboratoire de Physique des Interfaces et Couches Minces, UMR CNRS 7647, Academia Sinica, Institute of Atomic and Molecular Sciences Academia Sinica Taiwan
Contributors: Rondin, L., Dantelle, G., Slablab, A., Grosshans, F., Treussart, F., Bergonzo, P., Perruchas, S., Gacoin, T., Chaigneau, M., Chang, H. C., Jacques, V., Roch, J. F.
Publication date: 28 Sep 2010
Peer-reviewed: Yes

Publication information

Journal: Physical Review B
Volume: 82
Issue number: 11
Article number: 115449
ISSN (Print): 1098-0121
Ratings: 
  • Scopus rating (2010): SJR 3.318 SNIP 1.457
Original language: English
ASJC Scopus subject areas: Condensed Matter Physics, Electronic, Optical and Magnetic Materials
Source: Scopus
Source ID: 77957722876

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

Supercontinuum generation as a signal amplifier

Supercontinuum white-light generation in optical fibers is a process that is known for its extreme sensitivity toward fluctuations of the input pulses, giving rise to a strong amplification of input noise. Such noise amplification has been recognized as a detrimental effect that prevents compression of the broad white-light spectra into a few-cycle pulse. Here, we show that the same effect can be exploited to amplify and recover faint modulation signals to an extent that seems impossible with any electronic method. We experimentally demonstrate the deterministic amplification of faint amplitude modulation signals by up to 60 dB. As we show from numerical simulations, this amplification process arises from the interaction dynamics between solitons and dispersive radiation in the fiber. The resulting all-optic signal restoration provides a new photonic building block that enables signal processing at virtually unlimited processing speeds.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Optoelectronics Research Centre, Department of Physics, Research area: Optics, Research group: Nonlinear Fiber Optics, Frontier Photonics
Contributors: Orsila, L., Sand, J., Närhi, M., Genty, G., Steinmeyer, G.
Number of pages: 8
Pages: 757-764
Publication date: 2015
Peer-reviewed: Yes

Publication information

Journal: Optica
Volume: 2
Issue number: 8
ISSN (Print): 2334-2536
Ratings: 
  • Scopus rating (2015): CiteScore 3.5 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: Nonlinear optics, fibers, Ultrafast nonlinear optics, Ultrafast processing

Bibliographical note

ORG=orc,0.6
ORG=fys,0.4

Source: Scopus
Source ID: 84941207046

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 7.9 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

Suitability of Different Quench Protection Methods for a 16 T Block-Type Nb3Sn Accelerator Dipole Magnet

Within the future circular collider study, a 100-km long circular hadron collider is being designed for 100 TeV center-of-mass collision energies. The design of the 16 T Nb3Sn bending dipole magnets is carried out within the EuroCirCol collaboration. Three different type of dipole designs have been developed, each aiming to be as compact as possible, accounting for the design criteria. Quench protection a critical aspect of the magnet design and potentially limits the magnet compactness. The EuroCirCol magnets were designed assuming a protection system with significantly improved efficiency compared to the present LHC dipole protection. In this paper, we consider present state-of-the-art quench protection technologies, such as quench heaters and CLIQ, and apply them into the designed 16 T Block-type dipole. Two different simulation models are used to estimate the magnet hotspot temperature and voltages after a quench and consequently estimate the suitability of the different methods.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Electrical Energy Engineering, Research area: Electromagnetics, European Organization for Nuclear Research, Istituto Nazionale Di Fisica Nucleare, Frascati
Contributors: Salmi, T., Prioli, M., Stenvall, A., Ruuskanen, J., Verweij, A. P., Auchmann, B., Marinozzi, V.
Publication date: 1 Jun 2017
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Applied Superconductivity
Volume: 27
Issue number: 4
Article number: 4702305
ISSN (Print): 1051-8223
Ratings: 
  • Scopus rating (2017): CiteScore 2.7 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: CLIQ, hotspot temperature, quench protection heaters, quench simulation, Superconducting magnets
Electronic versions: 
Source: Scopus
Source ID: 85015258090

Research output: Contribution to journalArticleScientificpeer-review

Suitability of bundle approximation in AC loss analysis of NbTi wires: Simulations and experiment

Multifilamentary NbTi wires for ac applications are manufactured by embedding filament bundles into a metal matrix. In this stage of the manufacturing process, it is possible to affect the layout of the cross section and to choose whether to use few large or many small bundles in order to achieve a certain amount of filaments. All in all, up to 100 000 filaments are attainable for wire having the diameter of 1 mm. In this paper, ac loss measurements in external magnetic field on differently stacked NbTi samples are described. The measurements were performed in a LHe-cooled cryostat. The amplitude of the external field was varied between 250 mT and 3 T at frequencies of 0.02 and 0.12 Hz. We discuss possibilities to simulate the losses with finite element method. In particular, we concentrate on the filament bundle approximation and the possibilities to exploit it in the research and development process of new NbTi wires. In this approach, the filament bundles are considered as a homogenous mixture of matrix and superconducting filaments. According to the results, the bundle approximation greatly overestimates the losses. Furthermore, it should not be used for comparing, e.g., two wire structures where one has bundles of different size than the other. However, when considering how to situate the bundles on the cross section to achieve minimal ac loss, the bundle approximation can be a useful tool.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Electrical Engineering, Research area: Electromagnetics, University of Twente
Contributors: Lyly, M., Krooshoop, E., Lübkemann, R., Wessel, S., Stenvall, A., Dhalle, M., Mikkonen, R.
Publication date: 1 Jun 2015
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Applied Superconductivity
Volume: 25
Issue number: 3
ISSN (Print): 1051-8223
Ratings: 
  • Scopus rating (2015): CiteScore 2.5 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: AC loss, finite-element method (FEM), measurements, multifilamentary, NbTi, numerical modeling
Source: Scopus
Source ID: 84923303181

Research output: Contribution to journalArticleScientificpeer-review

Sub-parts-per-trillion sensitivity in trace gas detection by cantilever-enhanced photo-acoustic spectroscopy

We report a simple cantilever-enhanced photoacoustic detector, which reaches exceptionally good sensitivity in trace gas detection of hydrogen fluoride by using a highly stable narrow-linewidth optical parametric oscillator at 2.476 μm.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Photonics, University of Helsinki, Gasera Ltd.
Contributors: Tomberg, T., Vainio, M., Hieta, T., Halonen, L.
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: 85049146097

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

Sub-10 optical-cycle mode-locked Tm:(Lu2/3Sc1/3)2O3 mixed ceramic laser at 2057 nm

We present the first sub-10 optical-cycle bulk solid-state laser emitting in the 2-μm spectral range: A Tm3+:(Lu2/3Sc1/3)2O3 mixed ceramic laser mode-locked by a near-surface design GaSb-based SESAM produced nearly Fourier-limited pulses as short as 63 fs.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Photonics, Research group: ORC, Max Born Institute, China Academy of Engineering Physics, ITMO University, Jiangsu Normal University, Universitat Rovira i Virgili
Contributors: Wang, Y., Jing, W., Loiko, P., Zhao, Y., Huang, H., Suomalainen, S., Härkönen, A., Guina, M., Mateos, X., Griebner, U., Petrov, V.
Number of pages: 3
Publication date: 2017

Host publication information

Title of host publication: Advanced Solid State Lasers 2017 : Nagoya, Aichi Japan 1–5 October 2017
Publisher: The Optical Society; OSA
Article number: ATu6A.4
ISBN (Electronic): 978-0-9600380-7-7
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Mechanics of Materials
Source: Scopus
Source ID: 85039167684

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

Sub-100 ps monolithic diamond Raman laser emitting at 573 nm

We report a compact and efficient picosecond diamond Raman laser at 573 nm wavelength. The laser consists of a 0.5 mm thick single-crystal synthetic diamond coated to form a plane&#x2013;plane laser resonator, and pumped at 532 nm by a frequency-doubled Q-switched microchip laser system. The pump delivers 85 ps pulses at 100 kHz repetition rate at a maximum average power of &#x007E;500 mW. We demonstrate 1st Stokes emission from the diamond Raman laser with maximum power of 175 mW, corresponding to a conversion efficiency of 47&#x0025; and a pulse duration of 71 ps. Substantial pulse shortening is obtained by proper adjustment of the pump spot diameter on the diamond sample. A minimum pulse duration of 39 ps is reported for a conversion efficiency of 36&#x0025; and 150 mW output power. The simplicity of the architecture makes the system highly appealing as a yellow picosecond laser source.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Photonics, Research group: ORC, University of Strathclyde
Contributors: Nikkinen, J., Savitski, V., Reilly, S., Dziechciarczyk, L., Härkönen, A., Kemp, A., Guina, M.
Pages: 981-984
Publication date: 2018
Peer-reviewed: Yes
Early online date: 13 Feb 2018

Publication information

Journal: IEEE Photonics Technology Letters
Volume: 30
Issue number: 11
ISSN (Print): 1041-1135
Ratings: 
  • Scopus rating (2018): CiteScore 5.4 SJR 0.991 SNIP 1.272
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Atomic and Molecular Physics, and Optics, Electrical and Electronic Engineering
Keywords: Diamond, Diamond Raman lasers, Laser excitation, Lenses, Microchip lasers, Power generation, Pulsed lasers, Pump lasers, Q-switched lasers, Raman lasers, Stimulated emission, Visible lasers
Source: Scopus
Source ID: 85042062344

Research output: Contribution to journalArticleScientificpeer-review

Sub-100 fs pulse generation from a Tm,Ho: CALYO laser mode-locked by a GaSb-based SESAM at ~2043 nm

We report on the first sub-100-fs mode-locked Ho3+-laser in the 2-μm spectral range. The disordered co-doped Tm,Ho:CaYAlO4 (Tm,Ho:CALYO) crystal produced pulses as short as 87 fs with 27-mW average output power at 80.45-MHz repetition rate.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Photonics, Max Born Institute, Jiangsu Normal University, Universitat Rovira i Virgili, China Academy of Engineering Physics, ITMO University, Tongji University
Contributors: Zhao, Y., Wang, Y., Zhang, X., Mateos, X., Pan, Z., Loiko, P., Zhou, W., Xu, X., Xu, J., Shen, D., Suomalainen, S., Härkönen, A., Guina, M., Griebner, U., Petrov, V.
Publication date: 1 Jan 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: 85048984709

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

Study of second-harmonic generation from CdS nanostructured thin film

We investigate the second-order nonlinear optical properties of a nanostructured cadmium sulfide thin film by optical second-harmonic generation. The relative values of the components of the second-order susceptibility tensor are found to be 1, χ<inf>xxz</inf> = 0.14, χ <inf>zxx</inf> = and 0.07.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Department of Physics, Research area: Optics, Research group: Nonlinear Optics, Frontier Photonics, International School of Photonics, Cochin University of Science and Technology
Contributors: Mathew, S., Koskinen, K., Czaplicki, R., Pradeep, C., Kailasnath, M., GVallabhan, C. P., Kauranen, M., Radhakrishnan, P.
Number of pages: 4
Publication date: 19 Dec 2014

Host publication information

Title of host publication: 12th International Conference on Fiber Optics and Photonics
Publisher: Optical Society of America (OSA)
Article number: M4A.46
ISBN (Print): 9781557528827
ASJC Scopus subject areas: Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials

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

Study of quench protection for the Nb3Sn low-β quadrupole for the LHC luminosity upgrade (HiLumi-LHC)

The HiLumi program is aiming to develop and build new Nb3Sn, high-field (12 T), and large-aperture (150 mm) superconducting quadrupoles, which will be inserted in the LHC interaction regions and will provide the final focusing of the beam, in the program of luminosity upgrade. The quench protection of these magnets is one of the most challenging aspects, mainly because of the large value of the magnet inductance (160 mH for the configuration with two 8-m-long magnets in series), of the large value of the stored magnetic energy density in the coils (0.12 J/mm3, a factor 2 larger than in the conventional NbTi quadrupoles) and of the use of Nb3Sn as a conductor, which has never been used for large accelerator magnets. Previous works have demonstrated that a 'standard' conservative analysis, assuming quench heaters only on the coils' outer layer, gives high hot-spot temperature, close to the design limit (350 K). In this paper, a new study of quench protection is presented. The benefic effects of large dI/dt during the discharge and other dynamic effects are discussed together with options for having a partial coverage of the inner layer by quench heaters. The analysis is validated by experimental data from RD Nb3Sn quadrupole magnets.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Electrical Engineering, Università degli Studi di Milano, Fermi National Accelerator Laboratory, Lawrence Berkeley National Laboratory, European Organization for Nuclear Research
Contributors: Marinozzi, V., Ambrosio, G., Bellomo, G., Chlachidze, G., Felice, H., Marchevsky, M., Salmi, T., Sorbi, M., Todesco, E.
Publication date: 1 Jun 2015
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Applied Superconductivity
Volume: 25
Issue number: 3
Article number:  4002905
ISSN (Print): 1051-8223
Ratings: 
  • Scopus rating (2015): CiteScore 2.5 SJR 0.403 SNIP 1.046
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Electrical and Electronic Engineering
Keywords: Niobium compounds, quench protection, superconducting accelerators
Source: Scopus
Source ID: 84922823312

Research output: Contribution to journalArticleScientificpeer-review

Structure and in vitro dissolution of Mg and Sr containing borosilicate bioactive glasses for bone tissue engineering

Borosilicate bioactive glasses are promising for bone tissue engineering. The objective was to assess the impact of magnesium and/or strontium, when substituted for calcium on the glasses' thermal and dissolution properties. Both Mg and Sr substitution appeared to enhance the hot forming domain, i.e. the ability to hot process (sinter, draw fibres) without adverse crystallization. Structural analysis indicated that substitution of MgO and/or SrO for CaO results in changes in the BO3/BO4 ratio as well as in the ratio between bridging and non-bridging oxygen atoms in the silicate structure. Additionally, a de-shielding effect was noticed when Ca, Mg and Sr are present together in the glass network, possibly owing to PO4 3− charge-balanced preferentially by Na+. The Mg and/or Sr substitution resulted in a lower ion release in simulated body fluid and delayed formation of hydroxyapatite. However, once this layer formed it consisted of a Mg/Sr-substituted apatite. This work highlights the effect of combined ionic substitutions on bioactive glass structure and properties.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: BioMediTech, Research group: Biomaterials and Tissue Engineering Group, Friedrich-Schiller-University Jena, Universite de Rennes
Contributors: Tainio, J. M., Salazar, D. A. A., Nommeots-Nomm, A., Roiland, C., Bureau, B., Neuville, D. R., Brauer, D. S., Massera, J.
Number of pages: 10
Publication date: 1 Apr 2020
Peer-reviewed: Yes

Publication information

Journal: Journal of Non-Crystalline Solids
Volume: 533
Article number: 119893
ISSN (Print): 0022-3093
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Ceramics and Composites, Condensed Matter Physics, Materials Chemistry
Keywords: Bioactive glasses, Borosilicate glasses, In vitro dissolution, Structural properties, Tissue engineering
Source: Scopus
Source ID: 85078095947

Research output: Contribution to journalArticleScientificpeer-review

Structural and Electrical Characterization of Solution-Processed Electrodes for Piezoelectric Polymer Film Sensors

Solution-processable graphene and carbon nanotube-based electrode materials were used here to provide electrodes on flexible piezoelectric polyvinylidenefluoride sensors. Piezoelectric sensitivity measurements, image-based analysis, adhesion tests, and sheet resistance measurements
were applied to these printable sensors to rigorously analyze their performance and structure. The printable sensors showed electrical performance similar to metallized sensors, whereas the adhesion of the solution-processed materials to the substrate is not as high as that of the evaporated metal films. This also
affects the measured sensor sensitivity values. The measurements based on optical images were found to be a promising method to capture detailed information about the electrode surface structure.

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
Contributors: Rajala, S., Mettänen, M., Tuukkanen, S.
Number of pages: 8
Pages: 1692-1699
Publication date: 15 Mar 2016
Peer-reviewed: Yes

Publication information

Journal: IEEE Sensors Journal
Volume: 16
Issue number: 6
ISSN (Print): 1530-437X
Ratings: 
  • Scopus rating (2016): CiteScore 4.4 SJR 0.654 SNIP 1.697
Original language: English
ASJC Scopus subject areas: Biomedical Engineering, Electronic, Optical and Magnetic Materials, Surfaces and Interfaces
Keywords: Printed electrodes, image analysis, measurement, piezoelectric films, piezoelectric transducers, SHEAR-STRESS MEASUREMENTS, GRAPHENE, PVDF
Source: Bibtex
Source ID: urn:baf47c637d585669f900addd29c0f9bc

Research output: Contribution to journalArticleScientificpeer-review

Strong localization in unintentional disordered photonics crystal waveguides

Photonics crystal waveguide (PhCW), as a promising tool for realizing photonic integrated chip, can provide remarkable confinements of light field. In this report, we show that real PhCWs (i.e. PhCWs with fabrication imperfections left by state of the art fabrication facilities) without any intentional disorder support highly-confined localization states with a spatial extent comparable to that achieved with engineered micro-cavities [1]-[2].

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Frontier Photonics, Laboratoire Photonique Numérique et Nanosciences, CNRS
Contributors: Zang, X., Lalanne, P.
Number of pages: 3
Pages: 322-324
Publication date: 2013

Host publication information

Title of host publication: 2013 7th International Congress on Advanced Electromagnetic Materials in Microwaves and Optics, METAMATERIALS 2013
Publisher: IEEE COMPUTER SOCIETY PRESS
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials
Source: Scopus
Source ID: 84901218135

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 1.8 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

Stimuli-responsive photonic polymer coatings

This feature article focuses on the highlights in the development of photonic polymer coatings that can change their volume or surface topology in a reversible, dynamic fashion when exposed to an external stimulus. Topographic response is established using hydrogels or liquid crystal polymer networks. By changing the surface corrugation in response to light various functional coating properties can be modulated, for instance wettability and/or mechanical friction. The same volume changes in photonic coatings caused by different stimuli lead to changes in light reflection.

General information

Publication status: Published
MoE publication type: A2 Review article in a scientific journal
Organisations: Eindhoven University of Technology
Contributors: Stumpel, J. E., Broer, D. J., Schenning, A. P. H. J.
Number of pages: 10
Pages: 15839-15848
Publication date: 28 Dec 2014
Peer-reviewed: Yes

Publication information

Journal: Chemical Communications
Volume: 50
Issue number: 100
ISSN (Print): 1359-7345
Ratings: 
  • Scopus rating (2014): CiteScore 11.6 SJR 2.692 SNIP 1.427
Original language: English
ASJC Scopus subject areas: Chemistry(all), Catalysis, Ceramics and Composites, Electronic, Optical and Magnetic Materials, Surfaces, Coatings and Films, Materials Chemistry, Metals and Alloys

Bibliographical note

EXT="Stumpel, Jelle"

Source: Scopus
Source ID: 84911908006

Research output: Contribution to journalReview ArticleScientificpeer-review

Stimuli-Responsive Materials Based on Interpenetrating Polymer Liquid Crystal Hydrogels

Stimuli-responsive materials based on interpenetrating liquid crystal-hydrogel polymer networks are fabricated. These materials consist of a cholesteric liquid crystalline network that reflects color and an interwoven poly(acrylic acid) network that provides a humidity and pH response. The volume change in the cross-linked hydrogel polymer results in a dimensional alteration in the cholesteric network as well, which, in turn, leads to a color change yielding a dual-responsive photonic material. Furthermore a patterned coating having responsive and static interpenetrating polymer network areas is produced that changes both its surface topography and color.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Eindhoven University of Technology, School of Mathematical Sciences
Contributors: Stumpel, J. E., Gil, E. R., Spoelstra, A. B., Bastiaansen, C. W. M., Broer, D. J., Schenning, A. P. H. J.
Pages: 3314–3320
Publication date: 2015
Peer-reviewed: Yes

Publication information

Journal: Advanced Functional Materials
Volume: 25
Issue number: 22
ISSN (Print): 1616-301X
Ratings: 
  • Scopus rating (2015): CiteScore 20.4 SJR 4.859 SNIP 2.439
Original language: English
ASJC Scopus subject areas: Biomaterials, Electrochemistry, Condensed Matter Physics, Electronic, Optical and Magnetic Materials
Keywords: Cholesteric liquid crystals, Hydrogels, Interpenetrating polymer networks, Photonic materials, Smart materials

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 2.6 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

Statistical analysis of E-jet print parameter effects on Ag-nanoparticle ink droplet size

In this paper, we have studied the print parameter effects on electrohydrodynamic inkjet (E-jet) resolution using statistical analysis. In order to make the E-jet manufacturing process feasible, the effect of printing parameters on the ejected droplet size must be modelled and optimized. To this end, there exist two approaches: parameter effects can be modelled using theoretical calculations or they can be generated directly from empirical data using statistical analysis. The first option has been explored by multiple research groups, whereas the latter has received less interest. In this article, the effect of printing parameters on the width of AC-pulsed E-jet deposited Ag-nanoparticle ink droplets are investigated using design of experiments (DoE) approach and statistical analysis. As a result, a statistical model for deposited droplet width is generated using four print parameters (print height, bias voltage, peak voltage and frequency) as predictors. The model can predict 94.24% of the measured width variation with a standard deviation of 1.05 μm.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Electronics and Communications Engineering, Research group: Laboratory for Future Electronics, Research group: Wireless Communications and Positioning
Contributors: Laurila, M. M., Khorramdel, B., Dastpak, A., Mäntysalo, M.
Publication date: 2 Aug 2017
Peer-reviewed: Yes

Publication information

Journal: Journal of Micromechanics and Microengineering
Volume: 27
Issue number: 9
Article number: 095005
ISSN (Print): 0960-1317
Ratings: 
  • Scopus rating (2017): CiteScore 3.7 SJR 0.554 SNIP 1.015
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Mechanics of Materials, Mechanical Engineering, Electrical and Electronic Engineering
Keywords: design of experiments, E-jet, printed electronics, statistical analysis
URLs: 

Bibliographical note

INT=elt,"Dastpak, A."

Source: Scopus
Source ID: 85028383527

Research output: Contribution to journalArticleScientificpeer-review

State of polarization in anisotronic tapered fiber with extremely large core diameter

We produced numerical and experimental research of polarization maintaining properties of adiabatic anisotropic tapered optical fiber with extremely large output core diameter. Results show that polarization state of light coupling in the narrow end did not degrade dramatically through whole fiber length (while core diameter increasing adiabatically upto tens of wavelengths).

General information

Publication status: Published
Organisations: Optoelectronics Research Centre, Russian Quantum Center, Institute of Radio Engineering and Electronics of the Russian Academy of Sciences
Contributors: Ustimchik, V. E., Vyatkin, M. Y., Popov, S. M., Chamorovskii, Y. K., Filippov, V. N., Nikitov, S. A.
Pages: S123
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
Keywords: birefringence, large mode area fibers, polarization, taper fiber
Source: Scopus
Source ID: 84987880925

Research output: Other conference contributionPaper, poster or abstractScientific

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 3.6 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

Special Issue: Novel Optical and Photonic Devices based on 2D Materials

Since the isolation of graphene in 2004, two-dimensional (2D) materials with unique optical and electronic properties have attracted a wide interest and tremendous research, opening some promising applications in electronics, photonics and optoelectronics. This feature issue is aimed to capture the current state-of-the art, new trends and directions in 2D-material-based optical and photonic devices, and seven research articles are collected in this issue.

General information

Publication status: Published
MoE publication type: C2 Edited books
Organisations: Physics, Research group: Metaplasmonics, Xiamen University, Monash University, Swinburne University of Technology, Shenzhen University
Contributors: Luo, Z. (ed.), Bao, Q. (ed.), Caglayan, H. (ed.), Jia, B. (ed.), Zhang, H. (ed.)
Publication date: 2020
Peer-reviewed: Yes

Publication information

Journal: Optical Materials Express
Volume: 10
Issue number: 6
ISSN (Print): 2159-3930
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials

Research output: Contribution to journalSpecial issueScientificpeer-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 5 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

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 3.5 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

Solar Irradiation Independent Expression for Photovoltaic Generator Maximum Power Line

In order to enhance maximum power point tracking (MPPT) speed of photovoltaic generators (PVGs) upon fast irradiation changes, maximum power line (MPL)-based control is often used. MPL is a curve, linking all possible MPP coordinates for a given temperature. In the literature so far, PVG MPL was either assumed linear, which is inaccurate for all irradiation levels, or possessed photocurrent dependence, requiring real-time estimation of the latter. In this letter, an irradiation-independent explicit expression for PVG MPL is derived, valid for all practical irradiation levels, thus allowing real-time implementation without the need of photocurrent estimation.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Electrical Energy Engineering, Research group: Power electronics
Contributors: Kolesnik, S., Sitbon, M., Lineykin, S., Batzelis, E., Papathanassiou, S., Suntio, T., Kuperman, A.
Pages: 1416-1420
Publication date: 2017
Peer-reviewed: Yes

Publication information

Journal: IEEE Journal of Photovoltaics
Volume: 7
Issue number: 5
ISSN (Print): 2156-3381
Ratings: 
  • Scopus rating (2017): CiteScore 7.9 SJR 1.214 SNIP 1.499
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Electrical and Electronic Engineering
Keywords: Equivalent circuits, Estimation, maximum power line (MPL), Maximum power point tracking (MPPT), Multiprotocol label switching, Photoconductivity, photovoltaic generator (PVG), Photovoltaic systems, Radiation effects, single diode model
Electronic versions: 
Source: Scopus
Source ID: 85023754880

Research output: Contribution to journalArticleScientificpeer-review

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 20.4 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

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

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 15.3 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

Single KTiOPO4 nanocrystals for nonlinear probing of local optical fields and interaction with a metallic nanostructure

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: CNRS Centre National de la Recherche Scientifique, Laboratoire de Photonique Quantique et Moléculaire-ENS Cachan, UMR 8537, Laboratoire de Physique de la Matière Condensée-Ecole Polytechnique-CNRS, ESPCI, Laboratoire Photons Et Matière, UPR A0005, Ecole Polytechnique, Cristal Laser S.A.
Contributors: Slablab, A., Le Xuan, L., Zhou, C., Chauvat, D., De Wilde, Y., Perruchas, S., Tard, C., Gacoin, T., Villeval, P., Roch, J. F.
Publication date: 2009

Host publication information

Title of host publication: CLEO/Europe - EQEC 2009 - European Conference on Lasers and Electro-Optics and the European Quantum Electronics Conference
Article number: 5192089
ISBN (Print): 9781424440801
ASJC Scopus subject areas: Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials
Source: Scopus
Source ID: 70449578610

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

Single exposure lensless subpixel phase imaging

Lensless phase-retrieval system with phase modulation of free propagation wavefront is proposed. Contrary to the traditional super-resolution phase-retrieval, the method in this paper requires a single observation only and uses advanced SR-SPAR iterative technique. Successful object imaging relies on modulation of the object wavefront with a random phase-mask, which generates enlarged intensity patterns, allowing us to extract more information than it is possible without such a mask. The achieved high-quality super-resolution phase-imaging is demonstrated by simulation-tests produced with the parameters corresponding to the physical prototype of the considered optical system.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Computing Sciences, Research group: Computational Imaging-CI
Contributors: Kocsis, P., Shevkunov, I., Katkovnik, V., Egiazarian, K.
Number of pages: 9
Publication date: 2019

Host publication information

Title of host publication: Digital Optical Technologies 2019
Publisher: SPIE, IEEE
Editors: Kress, B. C., Schelkens, P.
ISBN (Electronic): 9781510628038

Publication series

Name: Proceedings of SPIE - The International Society for Optical Engineering
Volume: 11062
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: Diffractive optical element, Lensless imaging, Lensless system design, Phase imaging, Phase measurement, Phase retrieval, Sparse representation, Sub-pixel resolution
Source: Scopus
Source ID: 85074197001

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

Simulation studies of DFB laser longitudinal structures for narrow linewidth emission

Simulation studies targeting high-power narrow-linewidth emission from DFB lasers are presented. The linewidth and output power calculations take into account the mirror losses, including the grating and the facets, as well as spontaneous emission noise, effective refractive index, power and carrier density variations inside the cavity. The longitudinal power and carrier density distributions have been evaluated and their effects on longitudinal spatial hole burning and possible side mode lasing are discussed.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Optoelectronics Research Centre, Research group: Semiconductor Technology and Applications
Contributors: Virtanen, H., Uusitalo, T., Dumitrescu, M.
Number of pages: 2
Pages: 153-154
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): 9781467386036
ASJC Scopus subject areas: Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Modelling and Simulation, Numerical Analysis
Source: Scopus
Source ID: 84987641768

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

Simulation studies of DFB laser longitudinal structures for narrow linewidth emission

The paper presents simulation studies targeting high-power narrow-linewidth emission from semiconductor distributed feedback (DFB) lasers. The studies contain analytic and numerical calculations of emission linewidth, side mode suppression ratio and output power for DFB lasers without phase shifts and with 1 × λ/ 4 and 2 × λ/ 8 phase shifts, taking into account the grating and facets reflectivities, the randomness of the spontaneous emission and the longitudinal photon and carrier density distributions in the laser cavity. Single device structural parameter optimization is generally associated with a trade-off between achieving a narrow linewidth and a high output power. Correlated optimization of multiple structural parameters enables the evaluation of achievable ranges of narrow linewidth and high power combinations. Devices with long cavities and low grating coupling coefficients, κ (keeping κL values below the levels that promote re-broadening), with AR-coated facets and with a distributed phase-shift have the flattest longitudinal photon and carrier density distributions. This flatness enables stable single-longitudinal-mode operation with high side-mode-suppression ratio up to high injection current densities, which facilitates narrow linewidths and high output powers. The results reported in the paper indicate that Master-Oscillator Power-Amplifier laser structures are needed for achieving W-level high-powers with sub-MHz linewidths because most single-cavity DFB laser structural variations that reduce the linewidth also limit the achievable output power in single-mode operation.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Photonics, Research group: Semiconductor Technology and Applications
Contributors: Virtanen, H., Uusitalo, T., Dumitrescu, M.
Number of pages: 13
Publication date: 23 Mar 2017
Peer-reviewed: Yes

Publication information

Journal: Optical and Quantum Electronics
Volume: 49
Issue number: 4
Article number: 160
ISSN (Print): 0306-8919
Ratings: 
  • Scopus rating (2017): CiteScore 1.8 SJR 0.353 SNIP 0.631
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Atomic and Molecular Physics, and Optics, Electrical and Electronic Engineering
Keywords: Distributed feedback laser, High power, Narrow linewidth
Electronic versions: 
URLs: 
Source: Scopus
Source ID: 85016097411

Research output: Contribution to journalArticleScientificpeer-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

Simulation of cluster growth using a lattice gas model

Lattice gas models have been used to study the growth of icosahedral and fcc clusters. The simulations include adsorption, desorption, and diffusion of atoms to the nearest and next nearest lattice sites. A general survey of cluster growth is given from a diffusion dominated low pressure case to the adsorption dominated high pressure case. In general, clusters seem to grow monotonically without spending longer times at any cluster size. Compact clusters are observed only close to the limits of low and high pressures, and the growth is controlled either by diffusion or adsorption, accordingly. Both of these mechanisms can produce layer by layer type growth. When the layer by layer growth takes place only along (111) surfaces in fcc clusters, a reglar pattern is obtained in the abundance spectrum. This has the same frequency as the octahedral growth, even though the individual clusters are not perfect octahedra.

General information

Publication status: Published
MoE publication type: Not Eligible
Organisations: Jyväskylän yliopisto, Niels Bohr Institute
Contributors: Valkealahti, S., Manninen, M.
Number of pages: 11
Pages: 17564-17574
Publication date: 1 Jan 1994
Peer-reviewed: Yes

Publication information

Journal: Physical Review B
Volume: 50
Issue number: 23
ISSN (Print): 0163-1829
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Source: Scopus
Source ID: 0042150691

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 7.9 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

Short-range supercontinuum based lidar for combustion diagnostics

We developed a short range Lidar system using a supercontinuum source spectrally tailored to cover the ro-vibrational transition energies of desired components of a flue gas. The system enables simultaneous remote measurements of the gas parameters, like temperature and concentration which play a key role in the performance of combustion power plants. The technique requires only one inspection window and can thus be used in combustion units with limited access. It exploits differential absorption between specific wavelength bands of the gas absorption spectrum. The transmittance of individual wavelength band is derived from the detected backscattered temporal intensity of the supercontinuum pulses. We demonstrate preliminary industrial measurement of water vapor temperature and concentration in a full scale boiler. The technique also enables 3D mapping of temperature and concentration.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Physics, Valmet Technologies Oy
Contributors: Saleh, A., Ryczkowski, P., Genty, G., Toivonen, J.
Publication date: 2019

Host publication information

Title of host publication: SPIE Future Sensing Technologies
Publisher: SPIE, IEEE
Editors: Kimata, M., Valenta, C. R.
Article number: 111970Y
ISBN (Electronic): 9781510631113

Publication series

Name: Proceedings of SPIE
Volume: 11197
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: Combustion, Diagnostics, Lidar, Remote sensing, Supercontinuum

Bibliographical note

jufoid=71479

Source: Scopus
Source ID: 85078209433

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

SESAM mode-locked Tm: CALGO laser at 2 μm

GaSb-based SESAM is successfully employed for passive mode locking of a Tm3+: CaGdAlO4 laser operating near 2 μm. The pulse duration is around 650 fs at a repetition rate ∼100 MHz.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Research group: Semiconductor Technology and Applications, Optoelectronics Research Centre, Frontier Photonics, Max Born Institute, Shanghai Jiaotong University, Jiangsu Normal University, Vital Materials Co., Limited, Dipartimento di Ingegneria Industriale e Dell'Informazione, Universitat Rovira i Virgili, Belarusian National Technical University
Contributors: Wang, Y., Xie, G., Xu, X., Di, J., Qin, Z., Suomalainen, S., Guina, M., Härkönen, A., Agnesi, A., Griebner, U., Mateos, X., Loiko, P., Petrov, V.
Publication date: 2015

Host publication information

Title of host publication: Advanced Solid State Lasers, ASSL 2015
Publisher: Optical Society of America OSA
Article number: AW1A.2
ISBN (Print): 9781943580026
ASJC Scopus subject areas: Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials
Source: Scopus
Source ID: 84947590871

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

Sensitivity Analysis of Inverse Thermal Modeling to Determine Power Losses in Electrical Machines

Inverse analysis is a known mathematical approach, which has been used to solve physical problems of a particular nature. Nevertheless, it has seldom been applied directly for loss reconstruction of electrical machines. This paper aims to verify the accuracy of an inverse methodology used in mapping power loss distribution in an induction motor. Conjugate gradient method is used to iteratively find the unique inverse solution when simulated temperature measurement data are available. Realistic measurement situations are considered and the measurement errors corresponding to thermographic measurements and temperature sensor measurements are used to generate simulated numerical measurement data. An accurate 2-D finite-element thermal model of a 37 kW cage induction motor serves as the forward solution. The inverse model's objective is to map the power loss density in the motor accurately from noisy temperature measurements made on the motor housing's outer surface. Furthermore, the sensitivity of the adopted inverse methodology to variations in the number of available measurements is also considered. Filtering the applied noise to acceptable ranges is shown to improve the inverse mapping results.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Electrical Energy Engineering, Aalto University
Contributors: Nair, D. G., Rasilo, P., Arkkio, A.
Publication date: Nov 2018
Peer-reviewed: Yes
Early online date: 23 Jul 2018

Publication information

Journal: IEEE Transactions on Magnetics
Volume: 54
Issue number: 11
Article number: 8109405
ISSN (Print): 0018-9464
Ratings: 
  • Scopus rating (2018): CiteScore 3.1 SJR 0.539 SNIP 1.019
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Electrical and Electronic Engineering
Keywords: Heat transfer, Heating systems, induction motor, Induction motors, inverse problems, Loss measurement, Noise measurement, Stator windings, Temperature measurement
Electronic versions: 
Source: Scopus
Source ID: 85050587914

Research output: Contribution to journalArticleScientificpeer-review

Semantics of HTS AC Loss Modeling: Theories, Models, and Experiments

Computer-Assisted modeling is an essential approach to design new devices. It speeds up the process from the initial idea to an actual device and saves resources by reducing the number of built prototypes. This is also a significant practical motivator behind scientific research in contemporary high-Temperature superconductor (HTS) ac loss modeling. However, in the scientific literature in this field, consistent practices about modeling terminology have not been established. Then, it is up to the reader to decide, what is the true intent and meaning of the authors. Consequently, the interpretation of such literature might be very much reader dependent. An inseparable part of the whole modeling process is the development of modeling approaches and numerical methods and comparing the predictions obtained via modeling to experimentally achieved results. It is commonplace to discuss the accuracy of modeling results or the validation of a model. In this article, we discuss the terminology related to theories, models, and experiments in the context of HTS ac loss modeling. We discuss the recursive nature of theories and models in this context, discuss the compatibility of discrete formulations of physics utilized in our field with the corresponding continuum description, and interpret the perceived meaning of validation of a self-consistent model, shedding light on the relationships between theories, models, and measurements. We present our view on understanding these relations in the familiar context of ac losses in HTS, studying case examples through simulations and literature. As a result, we end this article with four conjectures describing our views.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Electrical Engineering
Contributors: Lahtinen, V., Stenvall, A.
Publication date: 1 Aug 2020
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Applied Superconductivity
Volume: 30
Issue number: 5
Article number: 5900809
ISSN (Print): 1051-8223
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Electrical and Electronic Engineering
Keywords: AC losses, experiment, high-Temperature superconductors (HTS), model, modeling, theory
Source: Scopus
Source ID: 85082393173

Research output: Contribution to journalArticleScientificpeer-review

Self-orienting liquid crystal doped with polymer-azo-dye complex

We investigate into a new type of liquid crystal (LC) heterogeneous system that contains hydrogen-bonded polymer-azo-dye complexes at a low concentration. The suspension shows a unique selforienting property and a spontaneous anchoring transition from planar to homeotropic alignment on a rubbed polyimide surface. We suggest a simple polymer adsorption model to explain the universal homeotropic orienting property. The complex-doped LC suspension can be used as a new liquid crystalline material that does not require any additional alignment processing or treatment.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Frontier Photonics, Aalto University, COMP Centre of Excellence, Department of Applied Physics, Aalto University
Contributors: Ouskova, E., Vapaavuori, J., Kaivola, M.
Number of pages: 8
Pages: 1463-1470
Publication date: 1 Dec 2011
Peer-reviewed: Yes

Publication information

Journal: Optical Materials Express
Volume: 1
Issue number: 8
ISSN (Print): 2159-3930
Ratings: 
  • Scopus rating (2011): CiteScore 0.7
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials
Source: Scopus
Source ID: 84862203301

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 4 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 4 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

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 2.7 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

Screen printed temporary tattoos for skin-mounted electronics

This paper focus on fabrication and analyzation of screen-printed temporary transfer electrical tattoos. Stretchable conductors and insulators are printed on temporary transfer tattoo paper. The printed lines are electrically and electromechanically characterized. Four different test structures were used to evaluate the sheet resistance and the quality of the printing process. The acquired sheet resistance of the tattoos was 42 mΩ/□ with a standard deviation of 6 mΩ/□. The maximum tensile strain before breaking was 19.4 %. Finally, on-skin performance was evaluated by attaching a printed tattoo on a knee and backhand of a test person. The skin-mounted tattoo showed good electrical performance and conformability.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Electrical Engineering, Research group: Wireless Communications and Positioning
Contributors: Tuominen, S., Mäntysalo, M.
Number of pages: 6
Pages: 1252-1257
Publication date: 1 May 2019

Host publication information

Title of host publication: IEEE 69th Electronic Components and Technology Conference, ECTC 2019
Publisher: IEEE
ISBN (Electronic): 9781728114989
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Electrical and Electronic Engineering
Keywords: Printed electronics, Stretchable electronics, Temporary electrical tattoo
Electronic versions: 

Bibliographical note

INT=elen,"Tuominen, Samuli"

Source: Scopus
Source ID: 85072291977

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

Screen-Printed Stretchable Interconnects

This article focuses on characterization of screen printed electrical interconnects for wearable applications. The interconnects are screen printed with stretchable silver-based ink on a thermoplastic polyurethane film. By optimizing the process parameters, we were able to fabricate 200 μm line widths with spacing of 200 μm. The average sheet resistance is 36.2 m/, however a significant lot-To-lot deviation was noted. In the strain tests, half of the samples have lost conductivity when 74.1% strain is reached. The normalized resistances of the samples rise linearly to approximately 30 % strain, after which the growth rate and deviation between samples increases significantly. It was also discovered that no cracking can be found from the traces while subjected to strains under 30%.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Electronics and Communications Engineering, Research group: Laboratory for Future Electronics, Department of Electronics and Communications Engineering
Contributors: Suikkola, J., Kankkunen, T., Iso-Ketola, P., Vanhala, J., Mäntysalo, M.
Number of pages: 6
Pages: 1650-1655
Publication date: 16 Aug 2016

Host publication information

Title of host publication: Proceedings - ECTC 2016: 66th Electronic Components and Technology Conference
Publisher: IEEE
ISBN (Electronic): 9781509012039
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Electrical and Electronic Engineering
Keywords: Printed electronics, Screen printed, Strechable, Wearable

Bibliographical note

INT=elt,"Kankkunen, Timo"
INT=elt,"Suikkola, Jari"

Source: Scopus
Source ID: 84987850149

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

Scalar diffraction field calculation from curved surfaces via Gaussian beam decomposition

We introduce a local signal decomposition method for the analysis of three-dimensional (3D) diffraction fields involving curved surfaces. We decompose a given field on a two-dimensional curved surface into a sum of properly shifted and modulated Gaussian-shaped elementary signals. Then we write the 3D diffraction field as a sum of Gaussian beams, each of which corresponds to a modulated Gaussian window function on the curved surface. The Gaussian beams are propagated according to a derived approximate expression that is based on the Rayleigh-Sommerfeld diffraction model. We assume that the given curved surface is smooth enough that the Gaussian window functions on it can be treated as written on planar patches. For the surfaces that satisfy this assumption, the simulation results show that the proposed method produces quite accurate 3D field solutions.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Signal Processing Research Community (SPRC), Bilkent University
Contributors: Şahin, E., Onural, L.
Number of pages: 11
Pages: 1459-1469
Publication date: 1 Jul 2012
Peer-reviewed: Yes

Publication information

Journal: Journal of the Optical Society of America A: Optics Image Science and Vision
Volume: 29
Issue number: 7
ISSN (Print): 1084-7529
Ratings: 
  • Scopus rating (2012): CiteScore 3.2 SJR 1.065 SNIP 1.198
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: 84863743776

Research output: Contribution to journalArticleScientificpeer-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 3.4 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

RF measurements to pinpoint defects in inkjet-printed, thermally and mechanically stressed coplanar waveguides

In this work 10-GHz-band RF measurement and microscopy characterizations were performed on thermally and mechanically long-term-stressed coplanar waveguides (CPW) to observe electrical and mechanical degradation in 1-mm-thick PPO/PPE polymer substrates with inkjet-printed Ag conductors. The structure contained two different CPW geometries in a total of 18 samples with 250/270 μm line widths/gaps and 670/180 μm line widths/gaps. A reliability test was carried out with three sets. In set #1 three 250 μm and three 670 μm lines were stored in room temperature conditions and used as a reference. In set #2 six samples were thermally cycled (TC) for 10,000 cycles, and in set #3 six samples were thermally cycled and bent with 6 mm and 8 mm bending diameters. Thermal stressing was done by cycling the samples in a thermal cycling test chamber operating at 0/100 °C with 15-minutes rise, fall, and dwell times, resulting in a one-hour cycle. The samples were analyzed during cycling breaks using a vector network analyzer (VNA). In addition to optical microscopy, field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) imaging were used to mechanically characterize the structures. The results showed that the line width of 670 μm had better signal performance and better long-term reliability than the line width of 250 μm. In this study, the average limit for proper RF operation was 2500 thermal cycles with both line geometries. The wide CPW lines provided more stable characteristics than the narrow CPW lines for the whole 10,000-cycle duration of the test, combined with repeated bending with a maximum bending radius of 6 mm. A phenomenon of nanoparticle silver protruding from cracks in the print of the bent samples was observed, as well as fracturing of the silver print in the CPW lines.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Electronics and Communications Engineering, Microelectronics Research, University of Oulu, Tampere University of Applied Sciences
Contributors: Myllymäki, S., Putaala, J., Hannu, J., Kunnari, E., Mäntysalo, M.
Number of pages: 9
Pages: 142-150
Publication date: 1 Oct 2016
Peer-reviewed: Yes

Publication information

Journal: Microelectronics Reliability
Volume: 65
ISSN (Print): 0026-2714
Ratings: 
  • Scopus rating (2016): CiteScore 2.6 SJR 0.447 SNIP 0.991
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Atomic and Molecular Physics, and Optics, Condensed Matter Physics, Safety, Risk, Reliability and Quality, Surfaces, Coatings and Films, Electrical and Electronic Engineering

Bibliographical note

EXT="Kunnari, Esa"
EXT="Myllymäki, Sami"

Source: Scopus
Source ID: 84992618636

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

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 16.4 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

Restoring Integral Images from Focal Stacks Using Compressed Sensing Techniques

This paper contains an original development of the compressed sensing technique for restoring integral images from a number of observed 2D images. The proposed data acquisition uses a conventional camera equipped with a horizontal 1D mask placed in the pupil plane of the lens. The compressed sensing style algorithm developed is based on a sparsity hypothesis imposed on 2D cross sections of the light field.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Signal Processing, Universidad de la Laguna, University of Connecticut
Contributors: Trujillo-Sevilla, J. M., Katkovnik, V., Javidi, B., Rodríguez-Ramos, J. M.
Number of pages: 6
Pages: 701-706
Publication date: 1 Jul 2016
Peer-reviewed: Yes

Publication information

Journal: Journal of Display Technology
Volume: 12
Issue number: 7
ISSN (Print): 1551-319X
Ratings: 
  • Scopus rating (2016): CiteScore 3.6 SJR 0.672 SNIP 1.209
Original language: English
ASJC Scopus subject areas: Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Keywords: Compressed sensing, focal stack, integral imaging
Source: Scopus
Source ID: 84976358976

Research output: Contribution to journalArticleScientificpeer-review

Resolving unoccupied electronic states with laser ARPES in bismuth-based cuprate superconductors

Angle-resolved photoemission spectroscopy (ARPES) is typically used to study only the occupied electronic band structure of a material. Here we use laser-based ARPES to observe a feature in bismuth-based superconductors that, in contrast, is related to the unoccupied states. Specifically, we observe a dispersive suppression of intensity cutting across the valence band, which, when compared with relativistic one-step calculations, can be traced to two final-state gaps in the bands 6 eV above the Fermi level. This finding opens up possibilities to bring the ultrahigh momentum resolution of existing laser-ARPES instruments to the unoccupied electron states. For cases where the final-state gap is not the object of study, we find that its effects can be made to vanish under certain experimental conditions.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Physics, Research group: Spectroscopies of Complex Materials, Computational Science X (CompX), Stanford University, California, Materials Sciences Division, Lawrence Berkeley National Laboratory, Northeastern University, Tohoku University, Department of Engineering and Applied Sciences, Sophia University, Electronics and Photonics Research Institute, National Institute of Advanced Industrial Science and Technology
Contributors: Miller, T. L., Ärrälä, M., Smallwood, C. L., Zhang, W., Hafiz, H., Barbiellini, B., Kurashima, K., Adachi, T., Koike, Y., Eisaki, H., Lindroos, M., Bansil, A., Lee, D. H., Lanzara, A.
Number of pages: 5
Publication date: 13 Feb 2015
Peer-reviewed: Yes

Publication information

Journal: Physical Review B
Volume: 91
Issue number: 8
Article number: 085109
ISSN (Print): 1098-0121
Ratings: 
  • Scopus rating (2015): CiteScore 6.8 SJR 2.377 SNIP 1.216
Original language: English
ASJC Scopus subject areas: Condensed Matter Physics, Electronic, Optical and Magnetic Materials
Source: Scopus
Source ID: 84922879533

Research output: Contribution to journalArticleScientificpeer-review

Residual stress development in cold sprayed Al, Cu and Ti coatings

Residual stresses play an important role in the formation and performance of thermal spray coatings. A curvature-based approach where the substrate-coating system deflection and temperature are monitored throughout the coating deposition process was used to determine residual stress formation during cold spray deposition of Al, Cu and Ti coatings. The effect of substrate material (carbon steel, stainless steel and aluminium) and substrate pre-treatment (normal grit blasting, grit blasting with the cold spray system and grinding for carbon steel substrate) were studied for all coating materials with optimized deposition parameters. Mainly compressive stresses were expected because of the nature of cold spraying, but also neutral as well as tensile stresses were formed for studied coatings. The magnitudes of the residual stresses were mainly dependent on the substrate/coating material combination, but the surface preparation was also found to have an effect on the final stress stage of the coating.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Engineering materials science and solutions (EMASS), VTT Technical Research Centre of Finland, Universitat Autonoma de Barcelona, Spain
Contributors: Suhonen, T., Varis, T., Dosta, S., Torrell, M., Guilemany, J. M.
Number of pages: 9
Pages: 6329-6337
Publication date: Oct 2013
Peer-reviewed: Yes

Publication information

Journal: Acta Materialia
Volume: 61
Issue number: 17
ISSN (Print): 1359-6454
Ratings: 
  • Scopus rating (2013): CiteScore 7.3 SJR 3.238 SNIP 2.66
Original language: English
ASJC Scopus subject areas: Ceramics and Composites, Metals and Alloys, Polymers and Plastics, Electronic, Optical and Magnetic Materials
Keywords: Aluminium, Cold spraying, Copper, Residual stresses, Titanium
Source: Scopus
Source ID: 84883740617

Research output: Contribution to journalArticleScientificpeer-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

Relaxation behavior of densified sodium aluminoborate glass

In this work, we study the relaxation behavior of a densified sodium aluminoborate glass by means of coupled Raman spectroscopy, Brillouin spectroscopy, and differential scanning calorimetry analyses. First, we show that the changes in elastic properties upon densification are largely associated with structural modifications in the glass network at short- and medium-range orders. Then, the evolution of the structural and elastic properties of the densified glass has been monitored in situ in the coupled DSC-Brillouin-Raman setup during isothermal annealing at different temperatures below the glass transition temperature. The stretched exponential function is found to well describe the observed relaxation kinetics, however, the stretching factor β varies non-monotonically with temperature. In contrast, the Arrhenius behavior of the characteristic decay times is deduced by lifetime distribution analysis, revealing three different relaxation processes with typical activation energies of 170±25, 200±5, and 280±15 kJ/mol. The relative contributions of these processes to the overall relaxation kinetics are found to vary with the temperature as well as the type of parameter considered (structural, elastic, or thermal), and hence, the relaxation kinetics cannot be properly understood using the stretched exponent function. The possible origins of the different relaxation processes are discussed.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Physics, Aalborg University, University of Erlangen-Nuremberg
Contributors: Veber, A., Smedskjaer, M., de Ligny, D.
Number of pages: 15
Pages: 153-167
Publication date: 1 Oct 2020
Peer-reviewed: Yes

Publication information

Journal: Acta Materialia
Volume: 198
ISSN (Print): 1359-6454
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Ceramics and Composites, Polymers and Plastics, Metals and Alloys
Keywords: Brillouin spectroscopy, Densified glass, Kinetics, Raman spectroscopy, Relaxation
Source: Scopus
Source ID: 85089428372

Research output: Contribution to journalArticleScientificpeer-review

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 0.9 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

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

Real-time measurements of nonlinear instabilities in optical fibers

We review recent advances in the real-time characterization of instabilities in nonlinear fiber optics systems. In particular, we show how these techniques can provide novel insight into the dynamics of ultrafast complex optical systems.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Photonics, UMR 6174
Contributors: Ryczkowski, P., Närhi, M., Billet, C., Merolla, J. M., Dudley, J. M., Genty, G.
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: 85049124778

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

Real-time full-field characterization of transient dissipative soliton dynamics in a mode-locked laser

Dissipative solitons are remarkably localized states of a physical system that arise from the dynamical balance between nonlinearity, dispersion and environmental energy exchange. They are the most universal form of soliton that can exist, and are seen in far-from-equilibrium systems in many fields, including chemistry, biology and physics. There has been particular interest in studying their properties in mode-locked lasers, but experiments have been limited by the inability to track the dynamical soliton evolution in real time. Here, we use simultaneous dispersive Fourier transform and time-lens measurements to completely characterize the spectral and temporal evolution of ultrashort dissipative solitons as their dynamics pass through a transient unstable regime with complex break-up and collisions before stabilization. Further insight is obtained from reconstruction of the soliton amplitude and phase and calculation of the corresponding complex-valued eigenvalue spectrum. These findings show how real-time measurements provide new insights into ultrafast transient dynamics in optics.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Photonics, UMR 6174
Contributors: Ryczkowski, P., Närhi, M., Billet, C., Merolla, J. M., Genty, G., Dudley, J. M.
Number of pages: 7
Pages: 221–227
Publication date: 2018
Peer-reviewed: Yes
Early online date: 5 Mar 2018

Publication information

Journal: Nature Photonics
Volume: 12
ISSN (Print): 1749-4885
Ratings: 
  • Scopus rating (2018): CiteScore 59.9 SJR 13.456 SNIP 8.761
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Atomic and Molecular Physics, and Optics
Source: Scopus
Source ID: 85042848951

Research output: Contribution to journalArticleScientificpeer-review

Real-time depth image-based rendering with layered dis-occlusion compensation and aliasing-free composition

Depth Image-based Rendering (DIBR) is a popular view synthesis technique which utilizes the RGB+D image format, also referred to as view-plus-depth scene representation. Classical DIBR is prone to dis-occlusion artefacts, caused by the lack of information in areas behind foreground objects, which appear visible in the synthesized images. A number of recently proposed compensation techniques have addressed the problem of hole filling. However, their computational complexity does not allow for real-time view synthesis and may require additional user input. In this work, we propose a hole-compensation technique, which works fully automatically and in a perceptually-correct manner. The proposed technique applies a two-layer model of the given RGB+D imagery, which is specifically tailored for rendering with free viewpoint selection. The main two components of the proposed technique are an adaptive layering of depth into relative 'foreground' and 'background' layers to be rendered separately and an additional blending filtering aimed at creating a blending function for aliasing cancellation during the process of view composition. The proposed real-time implementation turns ordinary view-plus-depth images to true 3D scene representations, which allow visualization in the fly-around manner.

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)
Contributors: Smirnov, S., Gotchev, A.
Publication date: 2015

Host publication information

Title of host publication: Proceedings of SPIE - The International Society for Optical Engineering
Publisher: SPIE
Article number: 93990T
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
Electronic versions: 
Source: Scopus
Source ID: 84928501129

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

Realization of Free-Space Long-Distance Self-Healing Bessel Beams

A new approach for generating long-distance self-healing Bessel beams, which is based on a ring-shaped (annular) lens and a spherical lens in 4f-configuration, is reported. With this, diffraction-free light evolution of a zeroth order Bessel beam over several meters is shown and available scaling opportunities that surpass current technologies by far are discussed. Furthermore, it is demonstrated how this setup can be adapted to create Bessel beam superpositions, realizing the longest ever reported optical conveyor beam and helicon beam, respectively. Last, the self-healing capabilities of the beams are tested against strong opaque and non-opaque scatterers, which again emphasizes the great potential of this new method.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Physics, Friedrich-Schiller-University Jena, UMR 6174, Fraunhofer Institute for Applied Optics and Precision Engineering IOF, Vacom GmbH, Institute of Applied Physics, Institut für Physik, Universität Rostock, Albert
Contributors: Vetter, C., Steinkopf, R., Bergner, K., Ornigotti, M., Nolte, S., Gross, H., Szameit, A.
Publication date: 1 Oct 2019
Peer-reviewed: Yes

Publication information

Journal: Laser and Photonics Reviews
Volume: 13
Issue number: 10
Article number: 1900103
ISSN (Print): 1863-8880
Ratings: 
  • Scopus rating (2019): CiteScore 16.9 SJR 4.014 SNIP 2.903
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Atomic and Molecular Physics, and Optics, Condensed Matter Physics
Keywords: beam-shaping, Bessel-beams, laser-technology, self-healing, telecommunication
Source: Scopus
Source ID: 85073597306

Research output: Contribution to journalArticleScientificpeer-review

Rational design of a printable, highly conductive silicone-based electrically conductive adhesive for stretchable radio-frequency antennas

Stretchable radio-frequency electronics are gaining popularity as a result of the increased functionality they gain through their flexible nature, impossible within the confines of rigid and planar substrates. One approach to fabricating stretchable antennas is to embed stretchable or flowable conductive materials, such as conductive polymers, conductive polymer composites, and liquid metal alloys as stretchable conduction lines. However, these conductive materials face many challenges, such as low electrical conductivity under mechanical deformation and delamination from substrates. In the present study, a silicone-based electrically conductive adhesive (silo-ECA) is developed that have a conductivity of 1.51×104 S cm -1 and can maintain conductivity above 1.11×103 S cm-1 , even at a large stain of 240%. By using the stretchable silo- ECAs as a conductor pattern and pure silicone elastomers as a base substrate, stretchable antennas can be fabricated by stencil printing or soft-lithography. The resulting antenna's resonant frequency is tunable over a wide range by mechanical modulation. This fabrication method is low-cost, can support large-scale production, has high reliability over a wide temperature range, and eliminates the concerns of leaking or delamination between conductor and substrate experienced in previously reported micro-fluidic antennas.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Sensing Systems for Wireless Medicine (MediSense), Georgia Institute of Technology, Chinese University of Hong Kong
Contributors: Li, Z., Le, T., Wu, Z., Yao, Y., Li, L., Tentzeris, M., Moon, K. S., Wong, C. P.
Number of pages: 7
Pages: 464-470
Publication date: 21 Jan 2015
Peer-reviewed: Yes

Publication information

Journal: Advanced Functional Materials
Volume: 25
Issue number: 3
ISSN (Print): 1616-301X
Ratings: 
  • Scopus rating (2015): CiteScore 20.4 SJR 4.859 SNIP 2.439
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Biomaterials, Condensed Matter Physics, Electrochemistry
Source: Scopus
Source ID: 84920994935

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 7.4 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

Rapid and facile synthesis of graphene oxide quantum dots with good linear and nonlinear optical properties

We herein report a rapid and effective method for the synthesis of graphene oxide quantum dots (GOQDs) with excellent linear and nonlinear optical properties. The GOQDs were prepared by chemical cutting of graphite oxide and characterized using Fourier transform infrared spectroscopy, X-ray diffraction, UV–Vis absorption spectroscopy, Raman spectroscopy and transmission electron microscopy. The Commission International de l’Éclairage 1931 chromaticity coordinates for GOQDs (x = 0.21, y = 0.23) demonstrated that highly pure blue-light emission was achieved upon 330 nm excitation wavelength. Optical nonlinearity measurements conducted at 532 nm using 5 ns laser pulses indicated saturable absorption behavior, which tends to the onset of reverse saturable absorption as the input light fluence was increased.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Physics, Research group: Nonlinear Optics, Research area: Optics, Mahatma Gandhi University, University of Johannesburg, Ultra-Fast and Nonlinear Optical Lab, Raman Research Institute, St Teresas’s College
Contributors: Sakho, E. H. M., Oluwafemi, O. S., Perumbilavil, S., Philip, R., Kala, M. S., Thomas, S., Kalarikkal, N.
Pages: 10926–10933
Publication date: 2016
Peer-reviewed: Yes

Publication information

Journal: Journal of Materials Science: Materials in Electronics
Volume: 27
Issue number: 10
ISSN (Print): 0957-4522
Ratings: 
  • Scopus rating (2016): CiteScore 2.6 SJR 0.469 SNIP 0.802
Original language: English
ASJC Scopus subject areas: Condensed Matter Physics, Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials, Electrical and Electronic Engineering
Source: Scopus
Source ID: 84975307980

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

Quench Protection Study of the Updated MQXF for the LHC Luminosity Upgrade (HiLumi LHC)

In 2023, the LHC luminosity will be increased, aiming at reaching 3000 fb-1 integrated over ten years. To obtain this target, new Nb3Sn low-β quadrupoles (MQXF) have been designed for the interaction regions. These magnets present a very large aperture (150 mm, to be compared with the 70 mm of the present NbTi quadrupoles) and a very large stored energy density (120 MJ/m3). For these reasons, quench protection is one of the most challenging aspects of the design of these magnets. In fact, protection studies of a previous design showed that the simulated hot spot temperature was very close to the maximum allowed limit of 350 K; this challenge motivated improvements in the current discharge modeling, taking into account the so-called dynamic effects on the apparent magnet inductance. Moreover, quench heaters design has been studied to be going into more details. In this paper, a protection study of the updated MQXF is presented, benefitting from the experience gained by studying the previous design. A study of the voltages between turns in the magnet is also presented during both normal operation and most important failure scenarios.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Electrical Engineering, Research area: Electromagnetics, Laboratorio Accelatori e Superconduttività Applicata, Fermi National Accelerator Laboratory, CERN
Contributors: Marinozzi, V., Ambrosio, G., Ferracin, P., Izquierdo Bermudez, S., Rysti, J., Salmi, T., Sorbi, M., Todesco, E.
Publication date: 1 Jun 2016
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Applied Superconductivity
Volume: 26
Issue number: 4
Article number: 4001805
ISSN (Print): 1051-8223
Ratings: 
  • Scopus rating (2016): CiteScore 2.6 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: Niobium compounds, quench protection, superconducting accelerators
Source: Scopus
Source ID: 84962420401

Research output: Contribution to journalArticleScientificpeer-review

Quench Protection Study of the Eurocircol 16 T cosθ Dipole for the Future Circular Collider (FCC)

After Large Hadron Collider will be turned off, a new, more energetic machine will be needed in order to explore unknown regions of the high-energy physics. For this reason, the project Future Circular Collider (FCC) has started, with the goal of developing a 100-km-circumference collider of 50 TeV proton beams. The Eurocircol collaboration is part of the FCC study under the European Community leadership, and it aims to develop a conceptual design of FCC till 2019. One of the main targets is to design a bending dipole able to reach 16 T operation magnetic field, in order to accomplish the size and energy constraints. Such a magnetic field can be reached using Nb3Sn conductors. One option under exploration is the Cosθ dipole, by INFN of Milano and Genova. Because of the high stored energy and the large current densities due to the conductor performances, quench protection is one of the most challenging aspects of the design. In this paper, the quench protection of the cosθ design is presented. A standard quench protection study is accompanied by a less conservative study which includes ac effects on the power dissipation inside the coils and on the magnet inductance, in order to not exclude preventively more convenient designs, and to develop a more performing magnet as possible.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Electrical Energy Engineering, Research area: Power engineering, Research group: Modelling and superconductivity, Università degli Studi di Milano, Istituto Nazionale Di Fisica Nucleare, Frascati
Contributors: Marinozzi, V., Bellomo, G., Caiffi, B., Fabbricatore, P., Farinon, S., Salmi, T., Sorbi, M., Stenvall, A., Volpini, G.
Publication date: 1 Jun 2017
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Applied Superconductivity
Volume: 27
Issue number: 4
Article number: 4702505
ISSN (Print): 1051-8223
Ratings: 
  • Scopus rating (2017): CiteScore 2.7 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: accelerator dipoles, Quench protection, superconducting magnets
Source: Scopus
Source ID: 85014850365

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

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

Protection Heater Design Validation for the LARP Magnets Using Thermal Imaging

Protection heaters are essential elements of a quench protection scheme for high-field accelerator magnets. Various heater designs fabricated by LARP and CERN have been already tested in the LARP high-field quadrupole HQ and presently being built into the coils of the high-field quadrupole MQXF. In order to compare the heat flow characteristics and thermal diffusion timescales of different heater designs, we powered heaters of two different geometries in ambient conditions and imaged the resulting thermal distributions using a high-sensitivity thermal video camera. We observed a peculiar spatial periodicity in the temperature distribution maps potentially linked to the structure of the underlying cable. Two-dimensional numerical simulation of heat diffusion and spatial heat distribution have been conducted, and the results of simulation and experiment have been compared. Imaging revealed hot spots due to a current concentration around high curvature points of heater strip of varying cross sections and visualized thermal effects of various interlayer structural defects. Thermal imaging can become a future quality control tool for the MQXF coil heaters.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Electrical Engineering, Lawrence Berkeley National Laboratory, Fermi National Accelerator Laboratory, European Center for Nuclear Physics
Contributors: Marchevsky, M., Turqueti, M., Cheng, D. W., Felice, H., Sabbi, G., Salmi, T., Stenvall, A., Chlachidze, G., Ambrosio, G., Ferracin, P., Izquierdo Bermudez, S., Perez, J. C., Todesco, E.
Publication date: 1 Jun 2016
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Applied Superconductivity
Volume: 26
Issue number: 4
Article number: 4003605
ISSN (Print): 1051-8223
Ratings: 
  • Scopus rating (2016): CiteScore 2.6 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: Quench Protection, Superconducting Magnets, Thermal Imaging
Source: Scopus
Source ID: 84964335731

Research output: Contribution to journalArticleScientificpeer-review

Properties of nematicons in low-birefringence nematic liquid crystals

We investigate a nonlinear self-focusing and nematicon generation in low birefringence nematic liquid crystals (NLCs), where Δn≈0.04. Nematicons are obtained for larger optical powers but they are more stable than in NLCs with standard birefringence, of the order of Δn≈0.2. Moreover, in low-birefringent NLCs, polarization components exchange energy in a nonlinear regime. Such behaviour is not observed in typical NLCs, where ordinary and extraordinary waves tend to propagate independently due to large walk off. The results of our experimental test are also compared with numerical simulations, using a fully vectorial BPM. Calculations and experimental results are in good qualitative and quantitative agreement.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Frontier Photonics, Politechnika Warszawska, University “Roma Tre”, Nonlinear Optics and OptoElectronics Lab
Contributors: Kwaśny, M., Laudyn, U. A., Sala, F. A., Piccardi, A., Alberucci, A., Karpierz, M. A., Assanto, G.
Number of pages: 3
Pages: 8-10
Publication date: 2013
Peer-reviewed: Yes

Publication information

Journal: Photonics Letters of Poland
Volume: 5
Issue number: 1
Ratings: 
  • Scopus rating (2013): CiteScore 1.8 SJR 0.349 SNIP 0.723
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials
Source: Scopus
Source ID: 84875728984

Research output: Contribution to journalArticleScientificpeer-review

Propagation dynamics of ultrabroadband terahertz beams with orbital angular momentum for wireless data transfer

We investigate an approach to short and medium-range wireless communications based on the use of terahertz beams possessing an orbital angular momentum (OAM) that allows for noise-resistant broadband carrier. A the- oretical model of the proposed beams generation is developed and numerical predictions are given for propagation and visualization of complex-structured THz beams, including ones carrying a unit topological charge on a large number of spectral components of broadband terahertz radiation. The assessment method which in our case is terahertz pulse time-domain holography allows for analyzing spatiooral and spatio-spectral evolution of arbitrary shaped THz wave trains during their propagation in free space and interaction with obstacles.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Electrical Engineering, ITMO University, University of Birmingham
Contributors: Kulya, M. S., Sokolenko, B., Gorodetsky, A., Petrov, N. V.
Publication date: 2020

Host publication information

Title of host publication: Broadband Access Communication Technologies XIV
Publisher: SPIE
Editors: Dingel, B. B., Tsukamoto, K., Mikroulis, S.
Article number: 113070J
ISBN (Print): 9781510633773
ISBN (Electronic): 9781510633780

Publication series

Name: Proceedings of SPIE - The International Society for Optical Engineering
Volume: 11307
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: THz radiation, Vortex beams, wireless data transfer

Bibliographical note

jufoid=71479

Source: Scopus
Source ID: 85081176736

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

Progress on HL-LHC Nb3Sn Magnets

The high-luminosity Large Hadron Collider (HL-LHC) project aims at allowing to increase the collisions in the LHC by a factor of ten in the decade 2025-2035. One essential element is the superconducting magnet around the interaction region points, where the large aperture magnets will be installed to allow to further reduce the beam size in the interaction point. The core of this upgrade is the Nb3Sn triplet, made up of 150-mm aperture quadrupoles in the range of 7-8 m. The project is being shared between the European Organization for Nuclear Research and the US Accelerator Upgrade Program, based on the same design, and on the two strand technologies. The project is ending the short model phase, and entering the prototype construction. We will report on the main results of the short model program, including the quench performance and field quality. A second important element is the 11 T dipole that replaces a standard dipole making space for additional collimators. The magnet is also ending the model development and entering the prototype phase. A critical point in the design of this magnet is the large current density, allowing increase of the field from 8 to 11 T with the same coil cross section as in the LHC dipoles. This is also the first two-in-one Nb3Sn magnet developed so far. We will report the main results on the test and the critical aspects.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Electrical Energy Engineering, Research area: Power engineering, Research group: Modelling and superconductivity, European Organization for Nuclear Research, Brookhaven National Laboratory, Fermi National Accelerator Laboratory, Lawrence Berkeley National Laboratory
Contributors: Todesco, E., Annarella, M., Ambrosio, G., Apollinari, G., Ballarino, A., Bajas, H., Bajko, M., Bordini, B., Bossert, R., Bottura, L., Cavanna, E., Cheng, D., Chlachidze, G., De Rijk, G., Dimarco, J., Ferracin, P., Fleiter, J., Guinchard, M., Hafalia, A., Holik, E., Izquierdo Bermudez, S., Lackner, F., Marchevsky, M., Loeffler, C., Nobrega, A., Perez, J. C., Prestemon, S., Ravaioli, E., Rossi, L., Sabbi, G., Salmi, T., Savary, F., Schmalzle, J., Stoynev, S., Strauss, T., Tartaglia, M., Vallone, G., Velev, G., Wanderer, P., Wang, X., Willering, G., Yu, M.
Publication date: 1 Jun 2018
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Applied Superconductivity
Volume: 28
Issue number: 4
Article number: 4008809
ISSN (Print): 1051-8223
Ratings: 
  • Scopus rating (2018): CiteScore 2.9 SJR 0.406 SNIP 0.987
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Electrical and Electronic Engineering
Keywords: niobium-tin, superconducting coils, Superconducting magnets, type II superconductors
Source: Scopus
Source ID: 85046361406

Research output: Contribution to journalArticleScientificpeer-review

Programming Photoresponse in Liquid Crystal Polymer Actuators with Laser Projector

A versatile, laser-projector-based method is demonstrated for programming alignment patterns into monolithic films of liquid crystal polymer networks. Complex images can be photopatterned into the polymer films with sub-100 μm resolution, using relatively short exposure times. The method is further used to devise both photochemically and photothermally driven actuators that can undergo distinct light-induced shape changes, dictated by the programmed alignment patterns. Deformation modes such as buckling and coiling, as well as miniature robotic devices such as a gripper and a light-responsive octopod, are demonstrated. The reported technique enables easy and cost-effective programmable actuation with relatively high throughput, thus significantly facilitating the design and realization of functional soft robotic actuators.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Chemistry and Bioengineering, Research group: Chemistry & Advanced Materials, University of Warsaw
Contributors: Wani, O. M., Zeng, H., Wasylczyk, P., Priimagi, A.
Publication date: 2018
Peer-reviewed: Yes
Early online date: 2017

Publication information

Journal: Advanced Optical Materials
Volume: 6
Issue number: 1
Article number: 1700949
ISSN (Print): 2195-1071
Ratings: 
  • Scopus rating (2018): CiteScore 10.2 SJR 2.711 SNIP 1.6
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Atomic and Molecular Physics, and Optics
Keywords: Azobenzene, Laser projectors, Liquid crystal, Patterning, Photoactuation, Photoalignment
Electronic versions: 
Source: Scopus
Source ID: 85037631675

Research output: Contribution to journalArticleScientificpeer-review

Processor core for 32 kbit/s G.726 ADPCM codecs

This paper describes an application specific DSP core designed to be used in a CCITT 32 kbit/s G.726 Adaptive Differential Pulse Code Modulation codec. The instruction set architecture and the programming model of the DSP core were derived from an algorithm profile and complexity analysis and the core was implemented using VHDL and logic synthesis. Architecture design efforts were concentrated on finding the minimum amount of hardware resources which could implement the required functionality within the clock cycle count limit. The result is a Harvard architecture processor core which can be used to implement the 32 kbit/s G.726 ADPCM encoding/decoding functions with very modest external instruction and data memory requirements. In a typical configuration the processor can perform a full encode decode operation for one sample in less than 1100 clock cycles. A gate-level implementation of less than 4000 gates of silicon area was created using logic synthesis for a standard cell technology.

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, Signaalinkäsittely
Contributors: Vehviläinen, J., Nurmi, J.
Number of pages: 4
Pages: 1932-1935
Publication date: 1995

Host publication information

Title of host publication: 1995 IEEE International Symposium on Circuits and Systems. ISCAS '95
Volume: 3
Publisher: IEEE
ISBN (Print): 0-7803-2570-2
ASJC Scopus subject areas: Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials
Source: Scopus
Source ID: 0029200296

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

Processing of printed silver patterns on an ETFE substrate

Printed electronics makes it possible to fabricate devices on thin and flexible substrates at a low cost and with simple processing. However, substrate characteristics can make patterning challenging. Here, we report our approach for processing printed silver patterns on an extremely hydrophobic ethylene-Tetrafluoroethylene (ETFE) foil substrate. The effects of selected surface modification methods on substrate characteristics and final print quality were studied, and the thermal characteristics of ETFE were determined. Conductive silver patterns were fabricated using both screen printing and inkjet printing techniques. Additionally, intense pulse light method was compared to thermal annealing as an alternative annealing method. The surface modification of ETFE was observed to affect ink wetting and print quality. It was concluded that the impact of the chosen annealing method on the final characteristics of the printed structures was significant.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Electronics and Communications Engineering, Trelic Ltd.
Contributors: Mikkonen, R., Lahokallio, S., Frisk, L., Mäntysalo, M.
Number of pages: 7
Pages: 1-7
Publication date: 31 Jul 2018

Host publication information

Title of host publication: Proceedings - 2018 IMAPS Nordic Conference on Microelectronics Packaging, NORDPAC 2018
Publisher: IEEE
Article number: 8423860
ISBN (Print): 9789526815053
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Electrical and Electronic Engineering
Keywords: DSC, ETFE, IPL, Printed electronics, TMA
Electronic versions: 

Bibliographical note

EXT="Lahokallio, Sanna"
EXT="Frisk, Laura"

Source: Scopus
Source ID: 85051476038

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

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 3.3 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

Preserving natural scene lighting by strobe-lit video

Capturing images in low light intensity, and preserving ambient light in such conditions pose significant problems in terms of achievable image quality. Either the sensitivity of the sensor must be increased, filling the resulting image with noise, or the scene must be lit with artificial light, destroying the aesthetic quality of the image. While the issue has been previously tackled for still imagery using cross-bilateral filtering, the same problem exists in capturing video. We propose a method of illuminating the scene with a strobe light synchronized to every other frame captured by the camera, and merging the information from consecutive frames alternating between high gain and high intensity lighting. The motion between the frames is compensated using motion estimation based on block matching between strobe-illuminated frames. The uniform lighting conditions between every other frame make it possible to utilize conventional motion estimation methods, circumventing the image registration challenges faced in fusing flash/non-flash pairs from non-stationary images. The results of the proposed method are shown to closely resemble those computed using the same filter based on reference images captured at perfect camera alignment. The method can be applied starting from a simple set of three frames to video streams of arbitrary lengths with the only requirements being sufficiently accurate syncing between the imaging device and the lighting unit, and the capability to switch states (sensor gain high/low, illumination on/off) fast enough.

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)
Contributors: Suominen, O., Gotchev, A.
Publication date: 2015

Host publication information

Title of host publication: Image Processing: Algorithms and Systems XIII
Publisher: SPIE
Article number: 939919
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: Ambient light, Bilateral filter, Computational photography, Image denoising, Low-light, Motion compensation
Electronic versions: 
Source: Scopus
Source ID: 84928473920

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

Preparation of water-based carbon nanotube inks and application in the inkjet printing of carbon nanotube gas sensors

Water-based carbon nanotube (CNT) is highly desirable for inkjet printing devices due to its environmentally benign and low-cost features. To improve the dispersion of CNT in water, oxygen-containing functional groups are introduced into the surface of CNT via an acid oxidation process. The CNT-based gas sensor is fabricated by inkjet printing, which shows a high sensitivity toward NO 2. The application of inkjet-printed CNT in a printed RF antenna for wireless sensing is also discussed.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Sensing Systems for Wireless Medicine (MediSense), Georgia Institute of Technology, Georgia Institute of Technology, School of Electrical and Computer Engineering, Georgia Tech Research Institute, Chinese University of Hong Kong
Contributors: Lin, Z., Le, T., Song, X., Yao, Y., Li, Z., Moon, K. S., Tentzeris, M. M., Wong, C. P.
Publication date: 2013
Peer-reviewed: Yes

Publication information

Journal: Journal of Electronic Packaging
Volume: 135
Issue number: 1
Article number: 011001
ISSN (Print): 1043-7398
Ratings: 
  • Scopus rating (2013): CiteScore 2 SJR 0.43 SNIP 0.804
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Mechanics of Materials, Computer Science Applications, Electrical and Electronic Engineering
Keywords: Carbon Nanotube, Inkjet Printing, Nanotechnology, Water-Based Ink, Wireless Gas Sensor
Source: Scopus
Source ID: 84878587853

Research output: Contribution to journalArticleScientificpeer-review

Precipitate formation in aluminium alloys: Multi-scale modelling approach

Ternary Al–Mg–Si alloys have been modelled based on a multi-scale approach that spans across atomistic and mesoscale models and uses theoretically determined parameters. First, a cluster expansion model for total energy has been trained for atomistic configurations (FCC lattice) based on the data from density functional simulations of electronic structure. Free energy curves as a function of solute (Mg, Si) concentrations and disorder have been obtained by using this parameterisation together with meta-dynamics Monte Carlo sampling. In addition, free energy data, surface tensions as well as strain energy using the linear elasticity theory have been collected to be combined for a mesoscale phase-field model. The application of this approach shows that the formation of a layered MgSi phase, with (100) planes, is a particularly stable solute aggregation motif within the Al host matrix. Moreover, the phase-field model demonstrates that the preferred shape of the MgSi precipitates is needle-like (in FCC), and they can act as precursors for the important and well-known β″-type precipitates which are formed by translating one Mg column by a 1/2 lattice vector. The results provide theoretical evidence that the solute aggregation into needle-like MgSi domains (precipitates) is an inherent property of Al-Mg-Si alloys, and that it takes place even without the presence of vacancies which is a precondition for the eventual formation β″ precipitates.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Physics, Research group: Materials and Molecular Modeling, Norwegian Univ. of Sci. and Technol.
Contributors: Kleiven, D., Akola, J.
Number of pages: 9
Pages: 123-131
Publication date: 15 Aug 2020
Peer-reviewed: Yes

Publication information

Journal: Acta Materialia
Volume: 195
ISSN (Print): 1359-6454
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Ceramics and Composites, Polymers and Plastics, Metals and Alloys
Keywords: Aluminium alloys, Cluster expansion, Multi-scale modelling, Nucleation, Phase-field
Source: Scopus
Source ID: 85086074670

Research output: Contribution to journalArticleScientificpeer-review

Power loss mechanisms in n-type modulation-doped AlGaAs/GaAsBi quantum well heterostructures

We report on the power loss mechanisms of hot electrons in as-grown and annealed n-type modulation-doped Al0.15Ga0.85As/GaAs1-xBix (x = 0 and 0.04) quantum well structures considering acoustic phonon interactions via the deformation potential (non-polar) and piezoelectric (polar) scatterings. The two-dimensional (2D) electron gas is heated by applying various electric fields under a steady-state magnetic field, and the effect of the applied electric field on the Shubnikov de Haas (SdH) oscillations is analyzed to investigate the power loss mechanism. The temperature of hot electrons (T e) has been obtained by comparing the lattice temperature and applied electric field dependencies of the SdH oscillation amplitude. The hot electron temperature is almost the same for both Bi-free and Bi-containing samples except for the sample annealed at a higher temperature (700 °C) than the growth temperature of GaAsBi. The electron temperature dependence of power loss is analyzed using current theoretical analytic models derived for 2D semiconductors. We find that energy relaxation occurs in the intermediate temperature regime, including mixing of piezoelectric and deformation potential scattering. The power loss of hot electrons is found to be proportional to (Teγ-TLγ) with γ in the range from 2.4 to 4.2, which indicates that the hot electron relaxation is due to acoustic phonon scatterings via unscreened deformation potential and piezoelectric scattering. It is found that deformation potential scattering is dominant over piezoelectric scattering in the Bi-free sample, while the incorporation of Bi into the GaAs lattice makes these processes comparable. After thermal annealing at lower than growth temperature (350 °C), the scattering mechanism switches from deformation potential to piezoelectric scattering. After thermal annealing at higher than growth temperature (700 °C), the theoretical model does not fit to the experimental results due to degradation of the sample.

General information

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

Publication information

Journal: Semiconductor Science and Technology
Volume: 35
Issue number: 9
Article number: 095038
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: acoustic phonon scattering, energy relaxation, hot electron in GaAsBi, n-type modulation doped GaAsBi quantum well, power loss
Source: Scopus
Source ID: 85090446844

Research output: Contribution to journalArticleScientificpeer-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

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
Ratings: 
  • Scopus rating (2013): CiteScore 0.9
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

Plasmon lifetime enhancement in a bright-dark mode coupled system

Metallic nanoparticles can localize the incident light to hot spots as plasmon oscillations, where the intensity can be enhanced by up to four orders of magnitude. Even though the lifetime of plasmons is typically short, it can be increased via interactions with quantum emitters, e.g., spaser nanolasers. However, molecules can bleach in days. Here, we study the lifetime enhancement of plasmon excitations due to the coupling with longer-lifetime dark plasmon modes. We apply an analytical model based on harmonic oscillators to demonstrate that a coupled system of bright and dark plasmon modes decays more slowly than the bright mode alone. Furthermore, exact solutions of the three-dimensional Maxwell equations, i.e., finite-difference time domain, demonstrate that the lifetime of the coupled system significantly increases at the hot spot, which is not predictable by far-field response. The decay of the overall energy of such a coupled system, which can be extracted from experimental absorption measurements, is substantially different from the decay of the hot spot field. This observation enlightens the plasmonic applications in which the hot spot intensity enables the detection of the optical responses.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Physics, Hacettepe University, Middle East Technical University
Contributors: Yildiz, B. C., Bek, A., Tasgin, M. E.
Number of pages: 8
Publication date: 16 Jan 2020
Peer-reviewed: Yes

Publication information

Journal: Physical Review B
Volume: 101
Issue number: 3
Article number: 035416
ISSN (Print): 2469-9950
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Source: Scopus
Source ID: 85078332332

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 4.4 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

Piezoresistive natural rubber-multiwall carbon nanotube nanocomposite for sensor applications

We explore, both experimentally and theoretically, the possibility to use a composite of natural rubber (NR) and multiwall carbon nanotubes (MWCNT) as a piezoresistive tensile sensor. As an essentially new feature relative to the previous work, we have performed a systematic study of the mechanism of the piezoresistance at large deformations in a wide range of MWCNT concentrations and crosslinking degrees of the host rubber material. In qualitative agreement with the previous work, the conductivity of the unstrained NR/MWCNT nanocomposite is shown to be adequately described by the percolation theory with the critical exponent evaluated to ∼2.31. Varying tensile stress-induced strains in the composite has been shown to results in a non-linear electrical response that cannot be described by simple modifications of the percolation theory. In order to explain the observed non-linear dependence of the resistance R of the composite on the strain ε, we have developed a scaling theory that relates this resistance to the structural changes in the conducting MWCNT network caused by deforming the host NR. Based on the obtained results, we discuss the ways of using the highly stretchable conductive elastomer composites as an efficient piezoresistive tensile sensor.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Materials Science, Rubber Technology Centre, Indian Institute of Technology Kharagpur, Vodafone Department of Mobile Communications Systems, University of Münster, Leibniz-Institut für Polymerforschung Dresden E.V.
Contributors: Selvan, N. T., Eshwaran, S. B., Das, A., Stöckelhuber, K. W., Wießner, S., Pötschke, P., Nando, G. B., Chervanyov, A. I., Heinrich, G.
Number of pages: 12
Pages: 102-113
Publication date: 1 Mar 2016
Peer-reviewed: Yes

Publication information

Journal: Sensors and Actuators, A: Physical
Volume: 239
ISSN (Print): 0924-4247
Ratings: 
  • Scopus rating (2016): CiteScore 4.8 SJR 0.787 SNIP 1.619
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Instrumentation, Condensed Matter Physics, Surfaces, Coatings and Films, Metals and Alloys, Electrical and Electronic Engineering
Keywords: Sensor rubber filler strain nano-composite conductivity
Source: Scopus
Source ID: 84955467512

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

Physisorption of benzene on a tin dioxide surface: Van der Waals interaction

An adsorption study of the benzene molecule on SnO 2 (110) surfaces with the density functional theory is extended to include the van der Waals interaction. We compare adsorption onto two model surfaces of SnO 2, oxygen rich (stoichiometric) and oxygen poor (reduced), considered as limiting cases of varying oxygen abundance. With the chosen van der Waals approach it is found that on the stoichiometric surface, where binding has both a covalent nature and an ionic nature, with the addition of the van der Waals interaction the adsorption energy becomes somewhat stronger. However, on the reduced surface, where binding was earlier predicted to be more physisorptionlike by using a standard generalized gradient approximation (GGA) approach, the van der Waals interaction increases the adsorption energy by a larger factor. Furthermore, three different local-density approximation and GGA functionals are compared, as corrected with the van der Waals scheme. It is found that the correction brings those three to reasonably similar descriptions of adsorption on both surfaces. © 2012 American Physical Society.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Physics
Contributors: Viitala, M., Kuisma, M., Rantala, T. T.
Number of pages: 5
Pages: 1-5
Publication date: 8 Feb 2012
Peer-reviewed: Yes

Publication information

Journal: Physical Review B
Volume: 85
Issue number: 8
Article number: 085412
ISSN (Print): 1098-0121
Ratings: 
  • Scopus rating (2012): CiteScore 6.6 SJR 3.173 SNIP 1.391
Original language: English
ASJC Scopus subject areas: Condensed Matter Physics, Electronic, Optical and Magnetic Materials

Bibliographical note

Contribution: organisation=fys,FACT1=1<br/>Publisher name: American Physical Society, APS

Source: researchoutputwizard
Source ID: 5539

Research output: Contribution to journalArticleScientificpeer-review

Physics and applications of photonic crystals

In this article, we investigate how the photonic band gaps and the variety of band dispersions of photonic crystals can be utilized for various applications and how they further give rise to completely novel optical phenomena. The enhancement of spontaneous emission through coupled cavity waveguides in a one-dimensional silicon nitride photonic microcrystal is investigated. We then present the highly directive radiation from sources embedded in two-dimensional photonic crystals. The manifestation of novel and intriguing optical properties of photonic crystals are exemplified experimentally by the negative refraction and the focusing of electromagnetic waves through a photonic crystal slab with subwavelength resolution.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Bilkent University
Contributors: Ozbay, E., Bulu, I., Aydin, K., Caglayan, H., Guven, K.
Number of pages: 9
Pages: 87-95
Publication date: Oct 2004
Peer-reviewed: Yes

Publication information

Journal: Photonics and Nanostructures - Fundamentals and Applications
Volume: 2
Issue number: 2
ISSN (Print): 1569-4410
Ratings: 
  • Scopus rating (2004): SJR 1.381 SNIP 1.278
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Atomic and Molecular Physics, and Optics, Condensed Matter Physics, Hardware and Architecture, Electrical and Electronic Engineering
Keywords: Coupled cavity waveguide, Left-handed material, Negative refraction, Photonic crystal, Spontaneous emission

Bibliographical note

EXT="Caglayan, Humeyra"

Source: Scopus
Source ID: 4544365267

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): CiteScore 11.6 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

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 7.9 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

Photoinduced surface patterning of azobenzene-containing supramolecular dendrons, dendrimers and dendronized polymers

Ionic complexes of azobenzenes and dendritic structures are shown to exhibit efficient light-induced mass transport upon irradiation with a light interference pattern. Surface-relief gratings (SRGs) with modulation depths of up to 550 nm were successfully inscribed. We compare the SRG formation in three generations of supramolecular dendrons, dendrimers, and dendronized polymers and demonstrate that the grating formation process is destructed by the existence of self-assembled structures as well as by overly large size of the dendronic complexes.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Frontier Photonics, COMP Centre of Excellence, Department of Applied Physics, Aalto University, Aalto University, Universit'e de Lorraine/CNRS, HCI e 486.1
Contributors: Vapaavuori, J., Priimagi, A., Soininen, A. J., Canilho, N., Kasëmi, E., Ruokolainen, J., Kaivola, M., Ikkala, O.
Number of pages: 12
Pages: 711-722
Publication date: 2013
Peer-reviewed: Yes

Publication information

Journal: Optical Materials Express
Volume: 3
Issue number: 6
ISSN (Print): 2159-3930
Ratings: 
  • Scopus rating (2013): CiteScore 3.8 SJR 1.757 SNIP 2.34
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials
Source: Scopus
Source ID: 84880408720

Research output: Contribution to journalArticleScientificpeer-review

Photoinduced Electron Transfer in CdSe/ZnS Quantum Dot-Fullerene Hybrids

Photoinduced electron transfer (ET) in CdSe/ZnS core-shell quantum dot (QD) - fullerene (COOH-C<inf>60</inf>) hybrids was studied by the means of time-resolved emission and absorption spectroscopy techniques. A series of four QDs with emission in the range 540-630 nm was employed to investigate the dependence of the electron transfer rate on the QD size. Emission of the QDs is quenched upon hybrid formation, and the quenching mechanism is identified as photoinduced electron transfer from the QD to the fullerene moiety due to the fullerene anion signature observed in transient absorption. In order to obtain quantitative information on the ET reaction, several kinetic data analysis techniques were used, including a conventional multiexponential fitting and a maximum entropy method for emission decay analysis, as well as a distributed decay model based on the Poisson distribution of fullerenes in the hybrids. The latter gradually simplifies the interpretation of the transient absorption spectra and indicates that the spectra of QD cations are essentially similar to those of neutral QDs, differing only by a minor decrease in the intensity and broadening. Furthermore, only a minor decrease in the ET rate with the increasing QD size was observed, the time constants being in the range 100-200 ps for all studied QDs. The charge recombination is extended to 10 ns or longer for all hybrids.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Frontier Photonics, Department of Chemistry and Bioengineering, Research group: Supramolecular photochemistry
Contributors: Virkki, K., Demir, S., Lemmetyinen, H., Tkachenko, N. V.
Number of pages: 12
Pages: 17561-17572
Publication date: 23 Jul 2015
Peer-reviewed: Yes

Publication information

Journal: Journal of Physical Chemistry C
Volume: 119
Issue number: 31
ISSN (Print): 1932-7447
Ratings: 
  • Scopus rating (2015): CiteScore 7.9 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)

Bibliographical note

INT=keb,"Demir, Sinem"

Source: Scopus
Source ID: 84938703282

Research output: Contribution to journalArticleScientificpeer-review

Photoinduced Electron Injection from Zinc Phthalocyanines into Zinc Oxide Nanorods: Aggregation Effects

Phthalocyanines (Pc) are well-known light-harvesting compounds. However, despite the tremendous efforts on phthalocyanine synthesis, the achieved energy conversion efficiencies for Pc-based dye-sensitized solar cells are moderate. To cast light on the factors reducing the conversion efficiency, we have undertaken a time-resolved spectroscopy study of the primary photoinduced reactions at a semiconductor-Pc interface. ZnO nanorods were chosen as a model semiconductor substrate with enhanced specific surface area. The use of a nanostructured oxide surface allows to extend the semiconductor-dye interface with a hole transporting layer (spiro-MeOTAD) in a controlled way, making the studied system closer to a solid-state dye-sensitized solar cell. Four zinc phthalocyanines are compared in this study. The compounds are equipped with bulky peripheral groups designed to reduce the self-aggregation of the Pcs. Almost no signs of aggregation can be observed from the absorption spectra of the Pcs assembled on a ZnO surface. Nevertheless, the time-resolved spectroscopy indicates that there are inter-Pc charge separation-recombination processes in the time frame of 1-100 ps. This may reduce the electron injection efficiency into the ZnO by more than 50%, pointing out to a remaining aggregation effect. Surprisingly, the electron injection time does not correlate with the length of the linker connecting the Pc to ZnO. A correlation between the electron injection time and the "bulkiness" of the peripheral groups was observed. This correlation is further discussed with the use of computational modeling of the Pc arrangements on the ZnO surface. (Figure Presented).

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Chemistry and Bioengineering, Research group: Chemistry & Advanced Materials, Instituto Madrileño de Estudios Avanzados (IMDEA)-Nanociencia, Universidad Autónoma de Madrid, Mersin University, South-Ukrainian National Pedagogical University
Contributors: Virkki, K., Hakola, H., Urbani, M., Tejerina, L., Ince, M., Martínez-Díaz, M. V., Torres, T., Golovanova, V., Golovanov, V., Tkachenko, N. V.
Number of pages: 12
Pages: 9594-9605
Publication date: 4 May 2017
Peer-reviewed: Yes

Publication information

Journal: Journal of Physical Chemistry C
Volume: 121
Issue number: 17
ISSN (Print): 1932-7447
Ratings: 
  • Scopus rating (2017): CiteScore 7.9 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: 85020915273

Research output: Contribution to journalArticleScientificpeer-review

Photoinduced bending upon pulsed irradiation in azobenzene-containing crosslinked liquid-crystalline polymers

We have investigated the photoresponsive behavior of homogeneously aligned low-azobenzene-concentration crosslinked liquid-crystalline polymers. We compared the thermal contraction and photocontraction of the films, and show that upon UV irradiation, they bend efficiently towards the actinic light source. The photoinduced bending is studied both under continuous-wave irradiation and irradiation with nanosecond pulses. Pulsed irradiation revealed that the photomechanical response can take place within sub-millisecond time scale, and that even a single laser pulse can cause the sample to bend.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Frontier Photonics, Tokyo Institute of Technology, Aalto University, Chuo University
Contributors: Shimamura, A., Priimagi, A., Mamiya, J. I., Kinoshita, M., Ikeda, T., Shishido, A.
Number of pages: 9
Pages: 405-413
Publication date: Sep 2011
Peer-reviewed: Yes

Publication information

Journal: Journal of Nonlinear Optical Physics and Materials
Volume: 20
Issue number: 4
ISSN (Print): 0218-8635
Ratings: 
  • Scopus rating (2011): CiteScore 0.8 SJR 0.245 SNIP 0.207
Original language: English
ASJC Scopus subject areas: Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials, Physics and Astronomy (miscellaneous)
Keywords: Azobenzene, Liquid crystal, Photocontraction, Photomobile materials, Pulsed irradiation
Source: Scopus
Source ID: 84861871012

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 3.7 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

Phosphate glasses with blue persistent luminescence prepared using the direct doping method

Phosphate glasses with the composition (90NaPO3-(10-x)Na2O-xNaF) (mol%) with x = 0 and 10 were prepared with blue persistent luminescence (PeL) using direct particles doping method. Commercial CaAl2O4:Eu2+,Nd3+ microparticles (MPs) with blue PeL were added in the glass melt at a lower temperature than the melting temperature. The PeL properties of the glasses were related to the diffusion of Al from the MPs to the glass occurring during the glass preparation, which was found to depend on the temperature at which the MPs are added in the melt and also on the time before casting the melt after adding the MPs. The glass with x = 0 can be prepared with homogeneous PeL if the MPs are added at 575 °C. This Tdoping temperature can be reduced to 550 °C by replacing Na2O by NaF in the glass.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Photonics, Turun Yliopisto/Turun Biomateriaalikeskus
Contributors: Ojha, N., Tuomisto, M., Lastusaari, M., Petit, L.
Pages: 151-156
Publication date: Jan 2019
Peer-reviewed: Yes
Early online date: 1 Jan 2018

Publication information

Journal: Optical Materials
Volume: 87
ISSN (Print): 0925-3467
Ratings: 
  • Scopus rating (2019): CiteScore 4.4 SJR 0.594 SNIP 1.068
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: CaAlO:Eu,Nd microparticles, Corrosion, Fluorophosphate glass, Persistent luminescence
Source: Scopus
Source ID: 85044951460

Research output: Contribution to journalArticleScientificpeer-review

Phase-coded computational imaging for depth of field extension

We present a computational imaging approach, combining a phase-coded computational camera with a corresponding CNN-based deblurring network, that enables extended depth of field images. The simulations demonstrate promising results achieving significant depth of field extension.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Computing Sciences
Contributors: Sahin, E., Akpinar, U., Gotchev, A.
Publication date: 13 May 2019

Host publication information

Title of host publication: Proceedings - Digital Holography and Three-Dimensional Imaging 2019
Publisher: Optical Society of America
ISBN (Electronic): 9781943580590
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Mechanics of Materials
Source: Scopus
Source ID: 85086015554

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

Performance of Solar Cell Grids based on Ag, Au, and Al for Cost-Effective Manufacturing

We report on the performance of contact grids based on Ag, Al, and Au applied to III-V multijunction solar cells. We compare their their suitability as grid metals from different perspectives, including price, mass-to-conductivity ratio, and abundance. The grid functionality was evaluated by performing charge transport experiments under simulated sunlight. The best solar cell performance was obtained for Ag contacts. On the other hand, Al and Ag provide the most cost-effective approach: when compared to Au for equal conductivities, the cost for the grid material being only about 1.1% in the case of Ag, and 0.7% for Al.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Physics, Research group: ORC
Contributors: Raappana, M., Aho, A., Aho, T., Isoaho, R., Anttola, E., Kajas, N., Polojärvi, V., Tukiainen, A., Guina, M.
Publication date: Oct 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

Bibliographical note

INT=PHYS, "Anttola, Elina"
INT=PHYS, "Kajas, Ninja"

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 3.6 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

Perfect magnetic mirror and simple perfect absorber in the visible spectrum

Known experimental artificial magnetic conductors for terahertz and optical frequencies are formed by arrays of nanoparticles of various shapes. In this paper, we show that artificial magnetic conductors for the visible spectrum can be realized as simple, effectively quasistatic resonating structures, where the effective inductance is due to the magnetic flux inside a uniform metal substrate, and the effective capacitance is due to electric polarization of a thin uniform dielectric cover. To illustrate the main potential application of artificial magnetic conductors, we concentrate on the perfect-absorption regime, achieved by adjusting the loss factor of the artificial magnetic conductor to match its real input impedance to free space. We provide approximate analytical design formulas and introduce a simple equivalent circuit to explain the physical mechanism of emulation of magnetic response and perfect absorption of light. A prototype of a nearly perfect absorber for optical (from green to ultraviolet) frequencies is designed and experimentally tested. The results confirm the theoretical predictions and show polarization insensitivity and angular independence of response in a wide range of incidence angles.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Optoelectronics Research Centre, Research group: Semiconductor Technology and Applications, Frontier Photonics, Aalto University, University of Texas at Austin
Contributors: Valagiannopoulos, C. A., Tukiainen, A., Aho, T., Niemi, T., Guina, M., Tretyakov, S. A., Simovski, C. R.
Publication date: 11 Mar 2015
Peer-reviewed: Yes

Publication information

Journal: Physical Review B
Volume: 91
Issue number: 11
Article number: 115305
ISSN (Print): 1098-0121
Ratings: 
  • Scopus rating (2015): CiteScore 6.8 SJR 2.377 SNIP 1.216
Original language: English
ASJC Scopus subject areas: Condensed Matter Physics, Electronic, Optical and Magnetic Materials
Source: Scopus
Source ID: 84926444192

Research output: Contribution to journalArticleScientificpeer-review

Passive UHF RFID-based user interface on a wooden surface

We present a passive ultra-high frequency (UHF) radio frequency identification (RFID)-based human-technology interface platform. The platform comprises of two dipole antennas and three integrated circuits (IC), each with a unique ID. The platform, which is fixed on a wooden table by cutting the antennas and antenna-IC interconnections from copper tape, can be used for push button and swipe controlling. Each IC can be activated, i.e., connected to the antennas, by touching with finger. As the RFID reader can be connected to any application through WIFI, these ICs can act as wireless input points integrated into furniture, items, and textiles, where they can be used as inputs to desired digital actions. The platform allows all connected devices to be controlled accurately and effortlessly, which will take the convenience of implementation and utilization of these systems to a new level. As a preliminary trial, the platform was tested by two people giving 200 random inputs and 98% and 99% success rates were achieved. Based on these results, this type of passive RFID-based solutions could be used for administrating interfaces that would administer wide variety of interaction modalities, such as touch or tangible interaction on flat surfaces (e.g., tabletop surfaces, walls, doors).

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: BioMediTech, Computing Sciences, Tampere University
Contributors: Mehmood, A., Vianto, V., He, H., Chen, X., Buruk, O. O., Ukkonen, L., Virkki, J.
Number of pages: 4
Pages: 1760-1763
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: 9021441
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

Passive resonance sensor based method for monitoring particle suspensions

Control of particle suspensions is needed in several modern industrial processes. A reason for the difficulty in this task has been the lack of a fast and reliable measurement. In this study, we tested the measurement of particle suspension by using a method based on a passive resonance sensor. The relative amounts of dispersing agent and aluminium oxide in the suspension were varied. The studied method yielded signals which depended on the complex permittivity of the suspension. The results indicated that we were able to measure information that can be used as feedback for the suspension preparation process. In addition, the tested instrumentation was simple and robust and thus this method may allow online measurements directly from the industrial processes.

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, Department of Materials Science, Research group: Ceramic materials, Engineering materials science and solutions (EMASS), Integrated Technologies for Tissue Engineering Research (ITTE), Smart Energy Systems (SES)
Contributors: Salpavaara, T., Järveläinen, M., Seppälä, S., Yli-Hallila, T., Verho, J., Vilkko, M., Lekkala, J., Levänen, E.
Number of pages: 7
Pages: 324-330
Publication date: 8 Jun 2015
Peer-reviewed: Yes

Publication information

Journal: Sensors and Actuators B: Chemical
Volume: 219
ISSN (Print): 0925-4005
Ratings: 
  • Scopus rating (2015): CiteScore 7.4 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: Complex permittivity, Inductive coupling, Passive resonance sensor, Slurry, Suspension

Bibliographical note

ORG=ase,0.5
ORG=mol,0.5

Source: Scopus
Source ID: 84930646590

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 3.5 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

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 0.4 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

Optimization of convectively cooled heat sinks

Many factors of heat sink, such as its size and mass, component locations, number of fins, and fan power affect heat transfer. Owing to the opposite effects of these factors on heat sink maximum temperature, we have now a multi-objective optimization problem. A typical optimization case consists of hundreds of heat sink temperature field evaluations, which would be impractical to do with CFD. Instead, we propose to combine analytical results of convection and numerical solution of conduction to address these so-called conjugated heat transfer problems. We solve heat conduction in a solid numerically using the finite volume method and tackle convection with the analytical equation of forced convection in a parallel plate channel.This model is suitable for forced and natural convection heat sinks, and we have verified its validity by comparing its results to measured data and CFD calculations. We use the model to improve two industrial examples, using a multi-objective version of the particle swarm optimization (PSO) algorithm. The first example is a forced convection heat sink composed of nine heat generating components at the base plate, and the other is a natural convection case with two components. In both cases, mass is minimized; the other criterion is maximum temperature for the forced convection case and heat sink outer volume for the natural convection case. Our method is many orders of magnitude faster than CFD. Additionally, we provide some LES results of pin fins with natural convection for further use in similar optimizations.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Chemistry and Bioengineering, Research group: Bio- and Circular Economy, Mechanical Engineering and Industrial Systems
Contributors: Lampio, K., Karvinen, R.
Pages: 473-479
Publication date: 2017
Peer-reviewed: Yes

Publication information

Journal: Microelectronics Reliability
Volume: 79
ISSN (Print): 0026-2714
Ratings: 
  • Scopus rating (2017): CiteScore 2.6 SJR 0.388 SNIP 0.907
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Atomic and Molecular Physics, and Optics, Condensed Matter Physics, Safety, Risk, Reliability and Quality, Surfaces, Coatings and Films, Electrical and Electronic Engineering
Keywords: Fin array, Forced convection, Heat sink, Multi-objective optimization, Natural convection, Pin fins
Source: Scopus
Source ID: 85020690970

Research output: Contribution to journalArticleScientificpeer-review

Optimization of an E3SPreSSO Energy-Extraction System for High-Field Superconducting Magnets

High-temperature superconducting magnets (HTS) suffer from slow quench propagation and have in large fraction high thermal margin. Due to the high thermal margin, quench protection systems (QPS) based on initiating large normal zones, with, e.g., quench protection heaters or CLIQ, are not effective with HTS, and energy extraction is needed. In large magnets, energy extraction with a single dump is not effective and new solutions are looked for. Recently, a concept E 3SPreSSO for HTS magnet protection has been presented in the scope of European project EuCARD-2. E 3 SPreSSO utilizes a series-connected bifilar HTS or LTS coil. In this work, we present a methodology to design QPS based on E 3 SPreSSO for HTS magnets. Then, we utilize this methodology to design and analyze the suitability of such QPS for a 20 T HTS accelerator dipole.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Electrical Energy Engineering
Contributors: Ruuskanen, J., Stenvall, A., Van Nugteren, J., Lahtinen, V.
Publication date: 1 Apr 2018
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Applied Superconductivity
Volume: 28
Issue number: 3
Article number: 4700805
ISSN (Print): 1051-8223
Ratings: 
  • Scopus rating (2018): CiteScore 2.9 SJR 0.406 SNIP 0.987
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Electrical and Electronic Engineering
Keywords: Accelerator magnets, HTS cables, modeling, quench protection

Bibliographical note

INT=eee,"Van Nugteren, Jeroen"

Source: Scopus
Source ID: 85041649824

Research output: Contribution to journalArticleScientificpeer-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 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

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 2.8 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

Optical Frequency Comb Photoacoustic Spectroscopy

We combine for the first time a mid-infrared optical frequency comb Fourier transform spectrometer with cantilever-enhanced photoacoustic detection and measure high-resolution broadband spectra of the fundamental band of methane in a few milliliter sample volume.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Physics, Energy Technology and Thermal Process Chemistry, University of Helsinki
Contributors: Sadiek, I., Mikkonen, T., Vainio, M., Toivonen, J., Foltynowicz, A.
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: 85069190764

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

Optical and topographic changes in water-responsive patterned cholesteric liquid crystalline polymer coatings

In this work, we present patterned water-responsive coatings, which alter both their topological and optical properties. The polymer coatings are based on a hydrogen-bonded cholesteric liquid crystalline polymer network. A two-step photopolymerization procedure leads to a patterned coating with repeating liquid crystalline and isotropic areas. The cholesteric liquid crystalline areas reflect green light, whilst the isotropic areas are transparent for visible light. Treatment with alkaline solution results in a hygroscopic polymer salt coating. When placed in demineralized water, the polymer films swells, leading to an enhancement of the surface topography structure in which the liquid crystalline areas swell more. Moreover, the pitch of the helical organization in the cholesteric areas increases due to this swelling leading to a color change from green to red.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Eindhoven University of Technology, School of Mathematical Sciences
Contributors: Stumpel, J. E., Broer, D. J., Bastiaansen, C. W. M., Schenning, A. P. H. J.
Publication date: 2014

Host publication information

Title of host publication: Proceedings of SPIE : Organic Photonics VI
Volume: 9137
Publisher: SPIE
Article number: 91370U
ISBN (Print): 9781628410853

Publication series

Name: Proceedings of SPIE: the International Society for Optical Engineering
Publisher: SPIE
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: cholesteric liquid crystals, patterned surfaces, responsive optical coatings, responsive surface topographies, water-responsive

Bibliographical note

EXT="Stumpel, Jelle"

Source: Scopus
Source ID: 84902324488

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

Open Material Property Library With Native Simulation Tool Integrations - MASTO

Reliable material property data is crucial for trustworthy simulations throughout different areas of engineering.Special care must be taken when materials at extreme conditions are under study. Superconductors and devices assembled from superconductors and other materials, like superconducting magnets, are often operated at such extreme conditions: at low temperatures under high magnetic fields and stresses.Typically, some library or database is used for getting the data. We have started to develop a database for storing all kind of material property data online called Open Material Property Library With Native Simulation Tool Integrations -- MASTO. Data can also depend on other data and it can be versioned to guarantee permanent access. Guiding idea in MASTO is to build easy-to-use integration for various programming languages, modelling frameworks and simulation software. Currently, a full-fledged integration is built for Matlab to allow users to fetch and use data with one-liners.In this paper we briefly review some of the material property databases commonly used in superconductor modelling, present a case study showing how selection of the material property data can influence the simulation results, and introduce the principal ideas behind MASTO.This work serves as the reference document for citing MASTO when it is used in simulations.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Electrical Energy Engineering
Contributors: Stenvall, A., Lahtinen, V.
Publication date: 2018
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Applied Superconductivity
ISSN (Print): 1051-8223
Ratings: 
  • Scopus rating (2018): CiteScore 2.9 SJR 0.406 SNIP 0.987
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Electrical and Electronic Engineering
Keywords: Data models, Databases, experimental data, Libraries, Material properties, material property database, NIST, numerical modelling, simulations, Superconducting magnets, Temperature
Source: Scopus
Source ID: 85041392089

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): CiteScore 1.5 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

Observation of unusual metal-semiconductor interaction and metal-induced gap states at an oxide-semiconductor interface: The case of epitaxial BaO/Ge(100) junction

Oxidation of semiconductor surfaces is known to cause defect states at oxide-semiconductor interfaces of various devices. In contrast, effects of the semiconductor interaction with non-oxygen elements at such junctions are still unclear. We present evidence for the interrelationship between a metal (non-oxygen)-semiconductor reaction and formation of the band-gap defect states at a buried oxide-semiconductor interface by investigating well-defined epitaxial BaO/Ge(100) junctions with high-resolution synchrotron-radiation photoelectron spectroscopy. The states that arise from the Ba-Ge interaction lead to Fermi-level pinning at 0.40eV above the valence band maximum, while the defect-free BaO/Ge(100) interface has a flat band structure.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Optoelectronics Research Centre, Research group: Semiconductor Technology and Applications, Frontier Photonics, Department of Physics and Astronomy, University of Turku, Russian Academy of Sciences, University of Turku, Turun Yliopisto/Turun Biomateriaalikeskus
Contributors: Kuzmin, M., Laukkanen, P., Yasir, M., Mäkelä, J., Tuominen, M., Dahl, J., Punkkinen, M. P. J., Kokko, K., Hedman, H. P., Moon, J., Punkkinen, R., Polojärvi, V., Korpijärvi, V. M., Guina, M.
Publication date: 20 Oct 2015
Peer-reviewed: Yes

Publication information

Journal: Physical Review B
Volume: 92
Issue number: 16
Article number: 165311
ISSN (Print): 1098-0121
Ratings: 
  • Scopus rating (2015): CiteScore 6.8 SJR 2.377 SNIP 1.216
Original language: English
ASJC Scopus subject areas: Condensed Matter Physics, Electronic, Optical and Magnetic Materials

Bibliographical note

EXT="Kokko, K."
EXT="Laukkanen, P."
EXT="Kuzmin, M."

Source: Scopus
Source ID: 84944790567

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): CiteScore 58.3 SJR 13.614 SNIP 7.931
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Atomic and Molecular Physics, and Optics
Source: Scopus
Source ID: 85073826086

Research output: Contribution to journalArticleScientificpeer-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

Observation of local electroluminescent cooling and identifying the remaining challenges

The cooling of a light emitting diode (LED) by photons carrying out more energy than was used to electrically bias the device, has been predicted decades ago. 1, 2 While this effect, known as electroluminescent cooling (ELC), may allow e.g. fabricating thermophotonic heat pumps (THP) providing higher efficiencies than the existing solid state coolers, 3 ELC at powers sufficient for practical applications is still not demonstrated. To study high-power ELC we use double diode structures (DDSs), which consist of a double heterojunction (DHJ) LED and a photodiode (PD) grown within a single technological process and, thus, enclosed in a cavity with a homogeneous refractive index. 4, 5 The presence of the PD in the structure allows to more directly probe the efficiency of the LED, without the need for light extraction from the system, reducing undesirable losses. Our analysis of experimentally measured I - V curves for both the LED and the PD suggests that the local efficiency of the high-performance LEDs we have fabricated is approximately 110%, exceeding unity over a wide range of injection current densities of up to about 100A/cm 2 . At present the efficiency of the full DDS, however, still falls short of unity, not allowing direct evidence of the extraction of thermal energy from the LED. Here we review our previous studies of DDS for high-power EL cooling and discuss in more detail the remaining bottlenecks for demonstrating high-power ELC in the DDS context: the LED surface states, resistive and photodetection losses. In particular we report our first surface passivation measurements. Further optimization therefore mainly involves reducing the influence of the surface states, e.g. using more efficient surface passivation techniques and optimizing the PD. This combined with the optimization of the DDS layer thicknesses and contact metallization schemes is expected to finally allow purely experimental observation of high-power ELC.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Physics, Aalto University
Contributors: Radevici, I., Sadi, T., Tripurari, T., Tiira, J., Ranta, S., Tukiainen, A., Guina, M., Oksanen, J.
Publication date: 2019

Host publication information

Title of host publication: Photonic Heat Engines : Science and Applications
Publisher: SPIE, IEEE
Editors: Seletskiy, D. V., Epstein, R. I., Sheik-Bahae, M.
Article number: 109360A
ISBN (Electronic): 9781510625143

Publication series

Name: Proceedings of SPIE - The International Society for Optical Engineering
Volume: 10936
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: Double diode structures, Electroluminescent cooling, III-V semiconductors, Quantum efficiency, Surface states

Bibliographical note

jufoid=71479

Source: Scopus
Source ID: 85065604697

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

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 3.5 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

Novel optical and photonic devices based on 2D materials: Feature issue introduction

Since the isolation of graphene in 2004, two-dimensional (2D) materials with unique optical and electronic properties have attracted a wide interest and tremendous research, opening some promising applications in electronics, photonics and optoelectronics. This feature issue is aimed to capture the current state-of-the art, new trends and directions in 2D-material-based optical and photonic devices, and seven research articles are collected in this issue.

General information

Publication status: Published
MoE publication type: B1 Article in a scientific magazine
Organisations: Physics, Research group: Metaplasmonics, Xiamen University, Monash University, Swinburne University of Technology, Shenzhen University
Contributors: Luo, Z., Bao, Q., Caglayan, H., Jia, B., Zhang, H.
Number of pages: 2
Pages: 1344-1345
Publication date: 2020
Peer-reviewed: No

Publication information

Journal: Optical Materials Express
Volume: 10
Issue number: 6
ISSN (Print): 2159-3930
Original language: English
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials
Source: Scopus
Source ID: 85085860812

Research output: Contribution to journalEditorialScientific

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

Novel Er3+ doped phosphate glass-ceramics for photonics

In this invited proceeding, we report our latest results on the development of Er3+ doped phosphate glass-ceramics. Those new glass-ceramics were processed using different techniques, such as direct doping of particles into the glass melt and glass-ceramics methods. First, we explain the challenges to balance the survival and dispersion of Er3+ doped particles when preparing phosphate glass-ceramics using the direct doping of particles. Then, we discuss the impact of the glass crystallization on the luminescence properties of Er3+ ions.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Photonics, Politecnico di Torino, Istituto Superiore Mario Boella, CSMFO Lab.
Contributors: Petit, L., Nguyen, H., Hongisto, M., Salminen, T., Hakkarainen, T., Lopez-Iscoa, P., Pugliese, D., Boetti, N. G., Milanese, D.
Publication date: 1 Sep 2017

Host publication information

Title of host publication: ICTON 2017 - 19th International Conference on Transparent Optical Networks
Publisher: IEEE COMPUTER SOCIETY PRESS
ISBN (Electronic): 9781538608586
ASJC Scopus subject areas: Computer Networks and Communications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials
Keywords: glass-ceramics, luminescence, nucleation and growth, particles-containing phosphate glasses

Bibliographical note

INT=fot,"Nguyen, H."
INT=fot,"Hongisto, M."
jufoid=72297

Source: Scopus
Source ID: 85030976055

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

Novel enhancement techniques for ultra-high-performance conformal wireless sensors and 'smart skins' utilizing inkjet-printed graphene

We introduce various novel techniques for the performance enhancement of nanotechnology-enabled wireless platforms utilizing inkjet-printed graphene thin films, especially for gas sensing applications in this paper. Compared to previously reported results (6% sensitivity after exposure to 500 ppm NH 3), we have improved the performance by nearly a factor of 10, increasing the sensitivity to 4.8% at 60 ppm. Key advancements to the reduced graphene oxide (rGO) thin film include: (i) drastically reduced (micron to nm) film thickness via surface modification techniques, specifically enhancing charge transport properties, and (ii) increased porosity obtained via a unique in-house developed nano-patterning process. The proposed graphene-based thin film approach could set the foundation for a plethora of novel wireless sensing and gas-reconfigurable communication platforms.

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: Le, T., Lin, Z., Wong, C. P., Tentzeris, M. M.
Number of pages: 4
Pages: 1640-1643
Publication date: 2013

Host publication information

Title of host publication: 2013 IEEE 63rd Electronic Components and Technology Conference, ECTC 2013
Article number: 6575792
ISBN (Print): 9781479902330
ASJC Scopus subject areas: Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials
Source: Scopus
Source ID: 84883371367

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, Research group: Biomaterials and Tissue Engineering Group, Physics, Research group: Photonics Glasses, 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

Bibliographical note

INT=phys,"Del Cerro, Paloma Roldan"
INT=bmte,"Teittinen, Henriikka"

Source: Scopus
Source ID: 85085038962

Research output: Contribution to journalArticleScientificpeer-review

No-reference visual quality assessment for image inpainting

Inpainting has received a lot of attention in recent years and quality assessment is an important task to evaluate different image reconstruction approaches. In many cases inpainting methods introduce a blur in sharp transitions in image and image contours in the recovery of large areas with missing pixels and often fail to recover curvy boundary edges. Quantitative metrics of inpainting results currently do not exist and researchers use human comparisons to evaluate their methodologies and techniques. Most objective quality assessment methods rely on a reference image, which is often not available in inpainting applications. Usually researchers use subjective quality assessment by human observers. It is difficult and time consuming procedure. This paper focuses on a machine learning approach for no-reference visual quality assessment for image inpainting based on the human visual property. Our method is based on observation that Local Binary Patterns well describe local structural information of the image. We use a support vector regression learned on assessed by human images to predict perceived quality of inpainted images. We demonstrate how our predicted quality value correlates with qualitative opinion in a human observer study. Results are shown on a human-scored dataset for different inpainting 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, Signal Processing Research Community (SPRC), Dept. of Radio-Electronics Systems, Don State Technical University
Contributors: Voronin, V. V., Frantc, V. A., Marchuk, V. I., Sherstobitov, A. I., Egiazarian, K.
Publication date: 2015

Host publication information

Title of host publication: Image Processing: Algorithms and Systems XIII
Publisher: SPIE
Article number: 93990U
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: Inpainting, Machine learning, Metric, Quality assessment, SVR, Visual salience
Source: Scopus
Source ID: 84928473922

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

Nonlocal soliton scattering in random potentials

We experimentally investigate the transport behaviour of nonlocal spatial optical solitons when launched in and interacting with propagation-invariant random potentials. The solitons are generated in nematic liquid crystals; the randomness is created by suitably engineered illumination of planar voltage-biased cells equipped with a photosensitive wall. We find that the fluctuations follow a super-diffusive trend, with the mean square displacement lowering for decreasing spatial correlation of the noise.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Physics, University “Roma Tre”, CNRS, Nonlinear Optics and OptoElectronics Lab, Optics Laboratory, Department of Physics, Tampere University of Technology
Contributors: Piccardi, A., Residori, S., Assanto, G.
Number of pages: 5
Publication date: 1 Jul 2016
Peer-reviewed: Yes

Publication information

Journal: Journal of Optics
Volume: 18
Issue number: 7
Article number: 07LT01
ISSN (Print): 2040-8978
Ratings: 
  • Scopus rating (2016): CiteScore 3.4 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, nematicons, random potential, scattering, spatial solitons
Source: Scopus
Source ID: 84978954030

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 0.9 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 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 5.1 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

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 1.3 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

Non-destructive and wireless monitoring of biodegradable polymers

A method for monitoring changes in biodegradable polymers during hydrolysis is proposed. This wireless and non-destructive method is based on inductively coupled passive resonance sensors embedded in the polymer shell. In this study, we prepared specimens using two poly(lactide-co-glycolide) copolymers possessing different degradation profiles. The copolymer embedded sensors were immersed in buffer solution and their resonance features were compared with periodically performed conventional polymer characterization methods. A clear difference was noticed in the wirelessly measured signals between the two tested copolymer materials. Also the reference methods showed clear differences between the degradation profiles of the copolymers. The wirelessly measured signals are likely to correlate to the structural changes in the materials during the hydrolysis. In the future, this technique could be used in the laboratory to provide easy-to-access in situ information about the polymers. Even the state of biodegradable polymer implants could be wirelessly monitored.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Faculty of Biomedical Sciences and Engineering, Research area: Microsystems, Research group: Sensor Technology and Biomeasurements (STB), Research group: Biomaterials an