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Simultaneous detection of methane, oxygen and water vapour utilising near-infrared diode lasers in conjunction with difference-frequency generation

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Author

Summary, in English

An all-diode-laser-based spectrometer is used for the simultaneous detection of methane, oxygen and water vapour. This is accomplished using a 760-nm diode laser and a 980-nm diode laser in conjunction with difference-frequency generation to 3.4 mum in a periodically poled lithium niobate crystal. Each of the output wavelengths is resonant with one of the molecular species. Simultaneous recordings over a 15-m open path of laboratory air are demonstrated. The recording scheme shows the wide applicability of a diode-laser-based difference-frequency spectrometer for the detection of molecular species in different wavelength ranges. By increasing the frequency of the 760-nm diode laser and decreasing the frequency of the 980-nm diode laser, a maximum continuous tuning range in the mid infrared of 3.6 cm(-1) is achieved. This enables the recording of several methane lines at atmospheric pressure. Pressure-dependence studies of methane lineshapes are also performed in an absorption cell. An indoor-air methane background level of 3 ppm is measured. The signal-to-noise ratio in the recorded methane spectra indicates that sub-ppm detection of methane at atmospheric pressure is feasible.

Department/s

Publishing year

2000

Language

English

Pages

853-857

Publication/Series

Applied Physics B

Volume

71

Issue

6

Document type

Journal article

Publisher

Springer

Topic

  • Atom and Molecular Physics and Optics

Status

Published

ISBN/ISSN/Other

  • ISSN: 0946-2171