Novel supercontinuum sensing and imaging techniques in the infrared
|Kustantaja||Tampere University of Technology|
|Tila||Julkaistu - 30 marraskuuta 2018|
|Nimi||Tampere University of Technology. Publication|
A particular spectral range which has recently attracted a wide interest is the midinfrared corresponding to the molecular ﬁngerprint region and the atmospheric transparency window. This, in turn, has triggered renewed research eﬀort into adapting existing technique to this particular range of the electromagnetic spectrum including the light sources and detection schemes. This thesis belongs to this trend and reports novel, proof-of-concept, broadband optical sensing and imaging techniques in the infrared using supercontinuum light, a class of light sources with unique properties. The techniques are experimentally demonstrated and their performances discussed.
Speciﬁcally, the thesis demonstrates incoherent broadband cavity enhanced absorption spectroscopy in the mid-infrared wavelength range from 3000 to 3450 nm. Multi-component gas detection with sub-ppm accuracy is achieved in this range, which constitutes the widest continuous detection range for this technique in the mid-infrared.
Cantilever-enhanced photoacoustic spectroscopy in the mid-infrared is also demonstrated for the ﬁrst time in this thesis. The approach is broadband and allows for higher photoacoustic signal intensity and enhanced signal-to-noise ratio as compared to conventional systems that use black-body radiation sources. The results oﬀer novel perspective for photoacoustic detection opening the door to sensitive broadband and compact analyzers in the mid-infrared spectral region.
Exploiting the shot-to-shot ﬂuctuations of an incoherent supercontinuum and the recent progress in ultrafast real-time spectral measurement techniques, the thesis ﬁnally reports on a novel proof-of-concept correlation sensing and imaging method in the form of spectral-domain ghost imaging. The method is fast, scan-free, and oﬀer new opportunities for remote sensing in scattering and absorbing media, or in spectral regions where sensitive detectors are lacking. Application of this technique to broadband spectroscopic measurements gases as well as for interferometric imaging of physical objects is demonstrated. One can legitimately anticipate that the work presented in this thesis will foster new ideas and developments for optical sensing and imaging.