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Optical Engineering

Standoff detection of turbulent chemical mixture plumes using a swept external cavity quantum cascade laser
Author(s): Mark C. Phillips; Brian E. Brumfield
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Paper Abstract

We demonstrate standoff detection of turbulent mixed-chemical plumes using a broadly tunable external cavity quantum cascade laser (ECQCL). The ECQCL was directed through plumes of mixed methanol/ethanol vapor to a partially reflective surface located 10 m away. The reflected power was measured as the ECQCL was swept over its tuning range of 930 to 1065  cm−1 (9.4 to 10.8  μm) at rates up to 200 Hz. Analysis of the transmission spectra though the plume was performed to determine chemical concentrations with a time resolution of 0.005 s. Comparison of multiple spectral sweep rates of 2, 20, and 200 Hz shows that higher sweep rates reduce effects of atmospheric and source turbulence, resulting in lower detection noise and more accurate measurement of the rapidly changing chemical concentrations. Detection sensitivities of 0.13 ppm*m for MeOH and 1.2 ppm*m for EtOH are demonstrated for a 200-Hz spectral sweep rate and normalized to a 1-s detection time.

Paper Details

Date Published: 21 August 2017
PDF: 9 pages
Opt. Eng. 57(1) 011003 doi: 10.1117/1.OE.57.1.011003
Published in: Optical Engineering Volume 57, Issue 1
Show Author Affiliations
Mark C. Phillips, Pacific Northwest National Lab. (United States)
Brian E. Brumfield, Pacific Northwest National Lab. (United States)

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