26 February 2001 Trace chemical vapor detection by photothermal interferometry
Author Affiliations +
Proceedings Volume 4205, Advanced Environmental and Chemical Sensing Technology; (2001) https://doi.org/10.1117/12.417441
Event: Environmental and Industrial Sensing, 2000, Boston, MA, United States
Photothermal interferometry has been demonstrated as a technique that can detect vapors with extremely high sensitivity (parts-per-trillion levels). Our present research uses a photothermal detection scheme that incorporates tunable sources and a modified Jamin interferometric design to provide high selectivity and sensitivity for organo-phosphate vapor detection. Two possible tunable excitation sources are being studied for this sensor technology, a tunable CO2 laser and difference frequency mixing of a tunable NIR laser with a fixed wavelength NIR laser in a nonlinear crystal. The modified Jamin design imparts superior vibrational immunity by ensuring both interferometer beams encounter common optical elements. Examining the two complementary optical outputs of the interferometer, phase shifts on microradian levels have been detected. Trace chemical vapor detection is accomplished by introducing the tunable excitation laser source across the path of one interferometer beam providing a phase shift due to absorptive heating. Preliminary results indicated parts-per-billion level detection of both DMMP and DIMP using ~ 400mW of CO2 laser power at appropriate wavelengths.
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Paul M. Pellegrino, Nicholas F. Fell, and James B. Gillespie "Trace chemical vapor detection by photothermal interferometry", Proc. SPIE 4205, Advanced Environmental and Chemical Sensing Technology, (26 February 2001); doi: 10.1117/12.417441; https://doi.org/10.1117/12.417441

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