title: 2f-wavelength modulation Fabry-Perot photothermal interferometry.
abstract: 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-1a 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.
authors.forename: Johannes P
authors.initials: JP
authors.lastname: Waclawek
authors.forename: Volker C
authors.initials: VC
authors.lastname: Bauer
authors.forename: Harald
authors.initials: H
authors.lastname: Moser
authors.forename: Bernhard
authors.initials: B
authors.lastname: Lendl