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Proceedings Paper

Control of quantum cascade laser sources in stand-off detection of trace explosives
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Paper Abstract

We pursue the development of an eye-safe stand-off technique suitable for the detection of trace explosives. As the active illumination sources, tunable quantum cascade lasers (QCLs) are employed in Mid-LWIR (long-wave infrared) in the range of 6 to 11 μm, which contains many spectral features from analytes of interest. Any fluctuation of the laser beam direction and/or beam profile is amplified at the sample position, which would lead to diminished performance of the detection technique, both in sensitivity and selectivity. Several beam stabilization approaches were conducted to overcome this challenge: 1) Using a KBr/diamond pellet as a diffuser in combination with a multimode fiber 2) Feedback stabilization of quantum cascade laser beam steering. The purpose of the first method is to make a temporally and spatially incoherent laser beam source through the multimode fiber and KBr/diamond pellet. The second approach is to stabilize the beam position by using an active feedback loop. We have demonstrated that beam wander and speckle noise were successfully suppressed by these approaches. Independently, we have developed a custom-built broadband laser source in the Mid-LWIR range consisting of several high power Fabry Perot (FP)-QCLs. The FP-QCLs were operated in both CW and pulsed modes at different diode temperatures, and the emission spectra were collected by a FTIR. For our future work, the output beams will be collimated to spectrally combine multi-QCLs and aligned toward the same target. Also, a spatial heterodyne spectrometer (SHS) will be applied to discriminate spectral and spatial information from a single snapshot.

Paper Details

Date Published: 13 May 2019
PDF: 12 pages
Proc. SPIE 10983, Next-Generation Spectroscopic Technologies XII, 109830G (13 May 2019); doi: 10.1117/12.2518734
Show Author Affiliations
Yohan Yoon, American Society for Engineering Education (United States)
U.S. Naval Research Lab. (United States)
Christopher J. Breshike, American Society for Engineering Education (United States)
U.S. Naval Research Lab. (United States)
Christopher A. Kendziora, U.S. Naval Research Lab. (United States)
Robert Furstenberg, U.S. Naval Research Lab. (United States)
R. Andrew McGill, U.S. Naval Research Lab. (United States)

Published in SPIE Proceedings Vol. 10983:
Next-Generation Spectroscopic Technologies XII
Richard A. Crocombe; Luisa T.M. Profeta; Abul K. Azad, Editor(s)

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