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

Michael E. Webber; Michael B. Pushkarsky; C. Kumar N. Patel

doi:10.1117/12.452104

23 September 2002 Ultrasensitive gas detection using diode lasers and resonant photoacoustic spectroscopy

Michael E. Webber, Michael B. Pushkarsky, C. Kumar N. Patel

Proceedings Volume 4817, Diode Lasers and Applications in Atmospheric Sensing; (2002) https://doi.org/10.1117/12.452104
Event: International Symposium on Optical Science and Technology, 2002, Seattle, WA, United States

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, α_minl, is 1.8x10^-8, the minimum detectable absorption coefficient, α_min, 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.

Citation Download Citation

Michael E. Webber, Michael B. Pushkarsky, and C. Kumar N. Patel "Ultrasensitive gas detection using diode lasers and resonant photoacoustic spectroscopy", Proc. SPIE 4817, Diode Lasers and Applications in Atmospheric Sensing, (23 September 2002); https://doi.org/10.1117/12.452104

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