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Title: Characterization of a swept external cavity quantum cascade laser for rapid broadband spectroscopy and sensing

The performance of a rapidly swept external cavity quantum cascade laser (ECQCL) system combined with an open-path Herriott cell was evaluated for time-resolved measurements of chemical species with broad and narrow absorption spectra. A spectral window spanning 1278 – 1390 cm -1 was acquired at a 200 Hz acquisition rate, corresponding to a tuning rate of 2x10 4 cm -1/s, with a spectral resolution of 0.2 cm -1. The capability of the ECQCL to measure < 100 ppbv changes in N 2O and F134A concentrations on millisecond timescales was demonstrated in simulated plume studies with releases near the open-path Herriott cell. Absorbance spectra measured using the ECQCL system exhibited noise-equivalent absorption coefficients of 5x10 -9 cm -1Hz -1/2. For a spectrum acquisition time of 5 ms, noise-equivalent concentrations (NEC) for N 2O and F134A were measured to be 70 and 16 ppbv respectively, which improved to sub-ppbv levels with averaging to 100 s. Noise equivalent column densities of 0.64 and 0.25 ppmv x m in 1 sec are estimated for N 2O and F134A.
Authors:
 [1] ;  [1] ;  [1] ;  [1]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Publication Date:
Report Number(s):
PNNL-SA-111759
Journal ID: ISSN 1094-4087; OPEXFF; NN2001000
Grant/Contract Number:
AC05-76RL01830
Type:
Accepted Manuscript
Journal Name:
Optics Express
Additional Journal Information:
Journal Volume: 23; Journal Issue: 20; Journal ID: ISSN 1094-4087
Publisher:
Optical Society of America (OSA)
Research Org:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
47 OTHER INSTRUMENTATION; 54 ENVIRONMENTAL SCIENCES; lasers; tunable; semiconductor lasers; quantum cascade; spectroscopy; infrared
OSTI Identifier:
1222058