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Proceedings Paper

Ultra-sensitive gas detection using diode lasers and resonant photoacoustic spectroscopy
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Paper Abstract

A novel trace-gas sensor system has been developed based on resonant photoacoustics, wavelength modulation spectroscopy, near-infrared diode lasers and optical fiber amplifiers that can achieve parts-per-billion sensitivity with a ten centimeter long sample cell and standard commercially-available optical components. An optical fiber amplifier with 500 mW output power is used to increase the photoacoustic signal by a factor of 25, and wavelength modulation spectroscopy is used to minimize the interfering background signal from window absorption in the sample cell, thereby improving the overall detection limit. This sensor is demonstrated with a diode laser operating near 1532 nm for detection of ammonia that achieves an ultimate sensitivity of less than 6 parts-per-billion. The minimum detectable fractional optical density, αminl, is 1.8x10-8, the minimum detectable absorption coefficient, αmin, is 9.5x10-10 cm-1, and the minimum detectable absorption coefficient normalized by power and bandwidth is 1.5x10-9 Wcm-1/&sqrt; Hz. These measurements represent the first use of fiber amplifiers to enhance photoacoustic spectroscopy, and this technique is applicable to all other species that fall within the gain curves of optical fiber amplifiers.

Paper Details

Date Published: 23 September 2002
PDF: 12 pages
Proc. SPIE 4817, Diode Lasers and Applications in Atmospheric Sensing, (23 September 2002); doi: 10.1117/12.452104
Show Author Affiliations
Michael E. Webber, Pranalytica, Inc. (United States)
Michael B. Pushkarsky, Pranalytica, Inc. (United States)
C. Kumar N. Patel, Pranalytica, Inc. (United States)

Published in SPIE Proceedings Vol. 4817:
Diode Lasers and Applications in Atmospheric Sensing
Alan Fried, Editor(s)

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