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

Mark C. Phillips, Brian E. Brumfield

Research output: Contribution to journalArticlepeer-review

15 Scopus citations

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 1065cm-1 (9.4 to 10.8μm) 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.

Original languageEnglish (US)
Article number011003
JournalOptical Engineering
Volume57
Issue number1
DOIs
StatePublished - Jan 1 2018
Externally publishedYes

Keywords

  • gas sensing
  • infrared spectroscopy
  • quantum cascade laser
  • standoff detection
  • tunable laser

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Engineering(all)

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