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Proceedings Paper

CW DFB-QCL and EC-QCL based sensor for simultaneous NO and NO2 measurements via frequency modulation multiplexing using multi-pass absorption spectroscopy
Author(s): Yajun Yu; Nancy P. Sanchez; Minhan Lou; Chuantao Zheng; Hongpeng Wu; Aleksander K. Głuszek; Arkadiusz J. Hudzikowski; Robert J. Griffin; Frank K. Tittel
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Paper Abstract

Nitrogen oxides (NOx), including nitric oxide (NO) and nitrogen dioxide (NO2) play important roles in determining the photochemistry of the ambient atmosphere, controlling the production of tropospheric ozone, affecting the concentration levels of the hydroxyl radical, and forming acid precipitation. A sensor system capable of simultaneous measurements of NO and NO2 by using a commercial 76 m astigmatic multi-pass gas cell (MPGC) was developed in order to enable fastresponse NOx detection. A continuous wave (CW), distributed-feedback (DFB) quantum cascade laser (QCL) and a CW external-cavity (EC) QCL were employed for targeting a NO absorption doublet at 1900.075 cm-1 and a NO2 absorption line at 1630.33 cm-1, respectively. Both laser beams were combined and transmitted through the MPGC in an identical optical path and subsequently detected by a single mid-infrared detector. A frequency modulation multiplexing scheme was implemented by modulating the DFB-QCL and EC-QCL at different frequencies and demodulating the detector signal with two Labview software based lock-in amplifiers to extract the corresponding second-harmonic (2f) components. Continuous monitoring of NO and NO2 concentration levels was achieved by locking the laser frequencies to the selected absorption lines utilizing a reference cell filled with high concentrations of NO and NO2. The experimental results indicate minor performance degradation associated with frequency modulation multiplexing and no cross talk between the two multiplexed detection channels. The performance of the reported sensor system was evaluated for real time, sensitive and precise detection of NO and NO2 simultaneously.

Paper Details

Date Published: 27 January 2017
PDF: 6 pages
Proc. SPIE 10111, Quantum Sensing and Nano Electronics and Photonics XIV, 1011108 (27 January 2017); doi: 10.1117/12.2251228
Show Author Affiliations
Yajun Yu, Rice Univ. (United States)
Wuhan Univ. (China)
Nancy P. Sanchez, Rice Univ. (United States)
Minhan Lou, Rice Univ. (United States)
Chuantao Zheng, Rice Univ. (United States)
Hongpeng Wu, Rice Univ. (United States)
Aleksander K. Głuszek, Rice Univ. (United States)
Arkadiusz J. Hudzikowski, Rice Univ. (United States)
Robert J. Griffin, Rice Univ. (United States)
Frank K. Tittel, Rice Univ. (United States)

Published in SPIE Proceedings Vol. 10111:
Quantum Sensing and Nano Electronics and Photonics XIV
Manijeh Razeghi, Editor(s)

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