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Proceedings Paper

Modeling of laser-analyte-substrate interaction in photo-thermal infrared imaging and laser trace vaporization
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Paper Abstract

We are developing two techniques for non-contact detection of explosives and other substances with low vapor pressure. In one approach, quantum cascade lasers (QCLs) at eye-safe power levels heat trace residues on surfaces at stand-off distances and the photo-thermal signal is imaged with an infrared camera. When using wavelengths corresponding to vibrational resonances specific to the trace molecules, the traces can be selectively heated and become visible in the infrared. In a second approach, a QCL or other IR laser of higher power is used to enhance the vapor signature of the analyte, thus facilitating vapor-based (e.g. ion mobility spectrometry) techniques. Details and advances in these techniques will be reported elsewhere. In this paper, we study the laser heating of analytes on substrates using the simulation software COMSOL. A model is validated with experimental results for particles of well characterized shape and size. The heat transfer between particle and substrate is of special interest, but not necessarily the dominant contributor to heat loss. Both air- and substrate-mediated heating of neighboring interferent particles is generally negligible. The presence of neighboring explosives particles affects the thermal kinetics via air-mediated heat transfer.

Paper Details

Date Published: 10 May 2011
PDF: 12 pages
Proc. SPIE 8013, Thermosense: Thermal Infrared Applications XXXIII, 801318 (10 May 2011); doi: 10.1117/12.883471
Show Author Affiliations
Robert Furstenberg, U.S. Naval Research Lab. (United States)
Jakob Großer, U.S. Naval Research Lab. (United States)
Christopher A. Kendziora, U.S. Naval Research Lab. (United States)
Michael R. Papantonakis, U.S. Naval Research Lab. (United States)
Viet Nguyen, U.S. Naval Research Lab. (United States)
R. Andrew McGill, U.S. Naval Research Lab. (United States)

Published in SPIE Proceedings Vol. 8013:
Thermosense: Thermal Infrared Applications XXXIII
Morteza Safai; Jeff R. Brown, Editor(s)

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