22 May 2015 Photoacoustic chemical sensing: layered systems and excitation source analysis
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Photoacoustic spectroscopy (PAS) is a versatile tool that is well suited for the ranged interrogation of layered samples. We have previously demonstrated standoff photoacoustic (PA) chemical detection of condensed phase samples at one meter distance using an interferometric sensing platform. Current research investigates layered solid samples constructed from a thin layer of energetic material deposited on a substrate. The PA signal from the system, as measured by the interferometer, changes based on the differing optical and mechanical properties of the substrate. This signal variance must be understood in order to develop a sensor capable of detecting trace quantities of hazardous materials independent of the surface. Optical absorption and modal excitation are the two biggest sources of PA signal generated in the sample/substrate system. Finally, the mode of operation of the excitation source is investigated. Most PA sensing paradigms use a quantum cascade laser (QCL) operating in either pulsed or modulated CW mode. We will discuss photoacoustic signal generation with respect to these different operating modes.
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Logan S. Marcus, Logan S. Marcus, Ellen L. Holthoff, Ellen L. Holthoff, Paul M. Pellegrino, Paul M. Pellegrino, "Photoacoustic chemical sensing: layered systems and excitation source analysis", Proc. SPIE 9455, Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XVI, 94550T (22 May 2015); doi: 10.1117/12.2176599; https://doi.org/10.1117/12.2176599

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