Standoff detection of turbulent chemical mixture plumes using a swept external cavity quantum cascade laser

Journal Article · Mon Aug 21 00:00:00 EDT 2017 · Optical Engineering

DOI:https://doi.org/10.1117/1.OE.57.1.011003· OSTI ID:1398208

Phillips, Mark C. ^[1]; Brumfield, Brian E. ^[1]

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1. Pacific Northwest National Laboratory, Richland, Washington

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 930-1065 cm-1 (9.4-10.8 µm) at rates up to 200 Hz. Analysis of the transmission spectra though the plume was performed to determine chemical concentrations with time resolution of 0.005 s. Comparison of multiple spectral sweep rates of 2 Hz, 20 Hz, 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, normalized to 1 s detection time.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1398208
• Report Number(s): PNNL-SA-126634; 45304036B
• Journal Information: Optical Engineering, Vol. 57, Issue 01; ISSN 0091-3286
• Publisher: SPIE
• Country of Publication: United States
• Language: English