Ultrasensitive detection technique for tunable diode laser spectrometers: application to detection of NO2 and H2O

David M. Sonnenfroh; Scott David Sewell; Mark G. Allen

doi:10.1117/12.255339

21 October 1996 Ultrasensitive detection technique for tunable diode laser spectrometers: application to detection of NO₂ and H₂O

David M. Sonnenfroh, Scott David Sewell, Mark G. Allen

Author Affiliations +

Proceedings Volume 2834, Application of Tunable Diode and Other Infrared Sources for Atmospheric Studies and Industrial Process Monitoring; (1996) https://doi.org/10.1117/12.255339
Event: SPIE's 1996 International Symposium on Optical Science, Engineering, and Instrumentation, 1996, Denver, CO, United States

Abstract

Recent advances in room-temperature tunable diode lasers and ultrasensitive electronic noise quieting detection techniques now enable a new generation of compact, optoelectronic, ultrasensitive trace gas sensors. These advances are key to producing sensors capable of routine and extended field use. We achieve near shot noise-limited signal detection using a novel, balanced ratiometric detector (BRD) which permits measurements of absorbances of 1:10⁶. High sensitivity is achieved by coupling this technology with an extended optical pathlength. The BRD is characterized by a wide linear dynamic range. A 10 Hz measurement rate enables ground level flux measurements or airborne concentration measurements. We will present an overview of two applications of our ultrasensitive detection technology to in situ atmospheric sensing. The first sensor is being developed to monitor boundary layer NO₂ fluxes. This sensor operates at 670 nm, utilizes an open multipass optical cell, and has a sub-ppbv detection sensitivity. The second sensor is an airborne, near IR diode laser hygrometer. The sensor uses an in-situ air measurement probe housing a 50 cm, open optical path to circumvent problems inherent in extractive sampling. The sensor is capable of measuring water vapor throughout the troposphere and has a sensitivity of 0.5 ppmv at the tropopause.

Citation Download Citation

David M. Sonnenfroh, Scott David Sewell, and Mark G. Allen "Ultrasensitive detection technique for tunable diode laser spectrometers: application to detection of NO₂ and H₂O", Proc. SPIE 2834, Application of Tunable Diode and Other Infrared Sources for Atmospheric Studies and Industrial Process Monitoring, (21 October 1996); https://doi.org/10.1117/12.255339

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