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

Mark C. Phillips; Brian E. Brumfield

doi:10.1117/1.OE.57.1.011003

21 August 2017 Standoff detection of turbulent chemical mixture plumes using a swept external cavity quantum cascade laser

Mark C. Phillips, Brian E. Brumfield

Author Affiliations +

Optical Engineering, Vol. 57, Issue 1, 011003 (August 2017). https://doi.org/10.1117/1.OE.57.1.011003

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.

Citation Download Citation

Mark C. Phillips and Brian E. Brumfield "Standoff detection of turbulent chemical mixture plumes using a swept external cavity quantum cascade laser," Optical Engineering 57(1), 011003 (21 August 2017). https://doi.org/10.1117/1.OE.57.1.011003

Received: 7 June 2017; Accepted: 26 July 2017; Published: 21 August 2017

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