7 October 2014 High reflected cubic cavity as long path absorption cell for infrared gas sensing
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Abstract
One direct and efficient method to improve the sensitivity of infrared gas sensors is to increase the optical path length of gas cells according to Beer-Lambert Law. In this paper, cubic shaped cavities with high reflected inner coating as novel long path absorption cells for infrared gas sensing were developed. The effective optical path length (EOPL) for a single cubic cavity and tandem cubic cavities were investigated based on Tunable Diode Laser Absorption Spectroscopy (TDLAS) measuring oxygen P11 line at 763 nm. The law of EOPL of a diffuse cubic cavity in relation with the reflectivity of the coating, the port fraction and side length of the cavity was obtained. Experimental results manifested an increase of EOPL for tandem diffuse cubic cavities as the decrease of port fraction of the connecting aperture f’, and the EOPL equaled to the sum of that of two single cubic cavities at f’<0.01. The EOPL spectra at infrared wavelength range for different inner coatings including high diffuse coatings and high reflected metallic thin film coatings were deduced.
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Jia Yu, Qiang Gao, Zhiguo Zhang, "High reflected cubic cavity as long path absorption cell for infrared gas sensing", Proc. SPIE 9220, Infrared Sensors, Devices, and Applications IV, 92200I (7 October 2014); doi: 10.1117/12.2072900; https://doi.org/10.1117/12.2072900
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