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Proceedings Paper

Trace chemical vapor detection by photothermal interferometry
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Paper Abstract

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.

Paper Details

Date Published: 26 February 2001
PDF: 6 pages
Proc. SPIE 4205, Advanced Environmental and Chemical Sensing Technology, (26 February 2001); doi: 10.1117/12.417441
Show Author Affiliations
Paul M. Pellegrino, Army Research Lab. (United States)
Nicholas F. Fell Jr., Army Research Lab. (United States)
James B. Gillespie, Army Research Lab. (United States)

Published in SPIE Proceedings Vol. 4205:
Advanced Environmental and Chemical Sensing Technology
Tuan Vo-Dinh; Stephanus Buettgenbach, Editor(s)

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