skip to main content


Title: CW EC-QCL-based sensor for simultaneous detection of H 2O, HDO, N 2O and CH 4 using multi-pass absorption spectroscopy

A sensor system based on a continuous wave, external-cavity quantum-cascade laser (CW EC-QCL) was demonstrated for simultaneous detection of atmospheric H 2O, HDO, N 2O and CH 4 using a compact, dense pattern multi-pass gas cell with an effective path-length of 57.6 m. The EC-QCL with a mode-hop-free spectral range of 1225-1285 cm -1 operating at similar to 7.8 mu m was scanned covering four neighboring absorption lines, for H 2O at 1281.161 cm -1, HDO at 1281.455 cm -1, N 2O at 1281.53 cm -1 and CH 4 at 1281.61 cm -1. A first-harmonic-normalized wavelength modulation spectroscopy with second-harmonic detection (WMS-2f/1f) strategy was employed for data processing. An Allan-Werle deviation analysis indicated that minimum detection limits of 1.77 ppmv for H 2O, 3.92 ppbv for HDO, 1.43 ppbv for N 2O, and 2.2 ppbv for CH 4 were achieved with integration times of 50-s, 50-s, 100-s and 129-s, respectively. In conclusion, experimental measurements of ambient air are also reported.
 [1] ;  [2] ;  [2] ;  [3]
  1. Rice Univ., Houston, TX (United States). Dept. of Electrical and Computer Engineering; Wuhan Univ., Wuhan (China). School of Electronic Information
  2. Rice Univ., Houston, TX (United States). Dept. of Civil and Environmental Engineering
  3. Rice Univ., Houston, TX (United States). Dept. of Electrical and Computer Engineering
Publication Date:
Grant/Contract Number:
AR0000545; AR0000547
Accepted Manuscript
Journal Name:
Optics Express
Additional Journal Information:
Journal Volume: 24; Journal Issue: 10; Journal ID: ISSN 1094-4087
Optical Society of America (OSA)
Research Org:
Rice Univ., Houston, TX (United States)
Sponsoring Org:
USDOE Advanced Research Projects Agency - Energy (ARPA-E)
Country of Publication:
United States
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; wavelength-modulation-spectroscopy; quantum-cascade laser; atmospheric nitrous-oxide; trace-gas detection; formaldehyde detection; water-vapor; methane; temperature; cell
OSTI Identifier: