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Applied Optics

Applied Optics

APPLICATIONS-CENTERED RESEARCH IN OPTICS

  • Vol. 39, Iss. 30 — Oct. 20, 2000
  • pp: 5609–5619

Shot-noise-limited dual-beam detector for atmospheric trace-gas monitoring with near-infrared diode lasers

Georges Durry, Ivan Pouchet, Nadir Amarouche, Théodore Danguy, and Gerard Megie  »View Author Affiliations


Applied Optics, Vol. 39, Issue 30, pp. 5609-5619 (2000)
http://dx.doi.org/10.1364/AO.39.005609


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Abstract

A dual-beam detector is used to measure atmospheric trace species by differential absorption spectroscopy with commercial near-infrared InGaAs laser diodes. It is implemented on the Spectromètre à Diodes Laser Accordables, a balloonborne tunable diode laser spectrometer devoted to the in situ monitoring of CH4 and H2O. The dual-beam detector is made of simple analogical subtractor circuits combined with InGaAs photodiodes. The detection strategy consists in taking the balanced analogical difference between the reference and the sample signals detected at the input and the output of an open optical multipass cell to apply the full dynamic range of the measurements (16 digits) to the weak molecular absorption information. The obtained sensitivity approaches the shot-noise limit. With a 56-m optical cell, the detection limit obtained when the spectra is recorded within 8 ms is ∼10-4 (expressed in absorbance units). The design and performances of both a simple substractor and an upgraded feedback substractor circuit are discussed with regard to atmospheric in situ CH4 absorption spectra measured in the 1.653-µm region. Mixing ratios are obtained from the absorption spectra by application of a nonlinear least-squares fit to the full molecular line shape in conjunction with in situP and T measurements.

© 2000 Optical Society of America

OCIS Codes
(010.1280) Atmospheric and oceanic optics : Atmospheric composition
(280.3420) Remote sensing and sensors : Laser sensors
(300.1030) Spectroscopy : Absorption
(300.6260) Spectroscopy : Spectroscopy, diode lasers
(300.6340) Spectroscopy : Spectroscopy, infrared
(300.6380) Spectroscopy : Spectroscopy, modulation

History
Original Manuscript: March 9, 2000
Revised Manuscript: July 5, 2000
Published: October 20, 2000

Citation
Georges Durry, Ivan Pouchet, Nadir Amarouche, Théodore Danguy, and Gerard Megie, "Shot-noise-limited dual-beam detector for atmospheric trace-gas monitoring with near-infrared diode lasers," Appl. Opt. 39, 5609-5619 (2000)
http://www.opticsinfobase.org/ao/abstract.cfm?URI=ao-39-30-5609

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