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J.P. Waclawek, V. Bauer, H. Moser, B. Lendl:
"2f-wavelength modulation Fabry-Perot photothermal interferometry";
Optics Express, 24 (2016), 25; 28958 - 28967.

Trace gas detection was performed by the principle of photothermal interferometry using a Fabry-Perot interferometer combined with wavelength modulation and second harmonic detection. The sensor employed a compact, low-volume gas cell in an overall robust set-up without the use of any moveable part. A quantum cascade laser was used as powerful mid-infrared excitation source to induce refractive index changes in the sample, whereas a near-infrared laser diode served as probe source to monitor the photo-induced variations. The functional principle of the selective sensor was investigated by detection of sulfur dioxide. For the targeted absorption band centered at 1379.78 cm−1 a 1 σ minimum detection limit of about 1 parts per million by volume was achieved. The work demonstrates high potential for further sensor miniaturization down to a sample volume of only a few mm3. Limitations and possible improvements of the sensor regarding sensitivity are discussed.

Fabry-Perot; Interferometry; Semiconductor lasers, quantum cascade; Spectroscopy, infrared; Spectroscopy, photothermal;

http://dx.doi.org/10.1364/OE.24.028958

http://publik.tuwien.ac.at/files/publik_255949.pdf