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Proceedings Paper

Recovery of ammonia absorption spectroscopy using asynchronous differential detection
Author(s): Menglong Cong; Dandan Sun
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Paper Abstract

This study proposes a complex design for the recovery of the line shape function of gas absorption spectrum. Laser power passing through trace gas is divided into real-time and delayed components, and the difference between them, regarded as equivalent to the first-order derivative spectrum, is recorded and integrated to reconstruct the absorption line profile. As the real-time and delayed signals are derived from the same gas cell and photo detector, the elimination of the background is more convenient and effective than in the generally used double-beam detection that involves two gas cells and photo detectors. Compared with the first harmonic detection used in wavelength modulation spectroscopy (WMS), the generation of the derivative spectrum is achieved without modulating the injection current of the laser. Moreover, the expensive lock-in amplifier in WMS is replaced by a simply designed device composed of an all-pass filter and an instrumentation amplifier. Complexity and cost are thus reduced significantly, and stability improves. For system validation, the absorption spectroscopy of ammonia from 4986.5 cm-1 to 4987.5 cm-1 was recovered, and the obtained data agreed well with the theoretical calculations.

Paper Details

Date Published: 12 December 2018
PDF: 6 pages
Proc. SPIE 10846, Optical Sensing and Imaging Technologies and Applications, 108460C (12 December 2018); doi: 10.1117/12.2503350
Show Author Affiliations
Menglong Cong, Inner Mongolia Univ. for the Nationalities (China)
Dandan Sun, Inner Mongolia Univ. for the Nationalities (China)


Published in SPIE Proceedings Vol. 10846:
Optical Sensing and Imaging Technologies and Applications
Mircea Guina; Haimei Gong; Jin Lu; Dong Liu, Editor(s)

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