Calibration of effective optical path length for hollow-waveguide based gas cell using absorption spectroscopy

Lin Liu; Zhenhui Du; Jinyi Li

doi:10.1117/12.2246928

1 November 2016 Calibration of effective optical path length for hollow-waveguide based gas cell using absorption spectroscopy

Lin Liu, Zhenhui Du, Jinyi Li

Author Affiliations +

Proceedings Volume 10157, Infrared Technology and Applications, and Robot Sensing and Advanced Control; 101572K (2016) https://doi.org/10.1117/12.2246928
Event: International Symposium on Optoelectronic Technology and Application 2016, 2016, Beijing, China

Abstract

The Hollow Waveguide (HWG) has emerged as a novel tool to transmit laser power. Owing to its long Effective Optical Path Length (EOPL) within a relatively small volume, it is suitable for the application as a gas cell in concentration measurement by using laser spectroscopy. The measurement of effective optical path length for a hollow waveguide, which possesses the physical length of 284.0 cm, by using Tunable Diode Laser Absorption Spectroscopy (TDLAS) was demonstrated. Carbon dioxide was used as a sample gas for a hollow waveguide calibration. A 2004 nm Distributed Feed-Back (DFB) laser was used as the light source to cover a CO₂ line near 2003 nm, which was selected as the target line in the measurement. The reference direct absorption spectroscopy signal was obtained by delivering CO₂ into a reference cell possessing a length of 29.4 cm. Then the effective optical path length of HWG was calculated by least-squares fitting the measured absorption signal to the reference absorption signal. The measured EOPL of HWG was 282.8 cm and the repeatability error of effective optical path length was calculated as 0.08 cm. A detection limit of 0.057 cm (with integral time 5 s) characterized by the Allan variance, was derived. The effective optical path length is obtained as the significant parameter to calculate the concentration of gases and it is of great importance to precise measurement of absorption spectroscopy.

Citation Download Citation

Lin Liu, Zhenhui Du, and Jinyi Li "Calibration of effective optical path length for hollow-waveguide based gas cell using absorption spectroscopy", Proc. SPIE 10157, Infrared Technology and Applications, and Robot Sensing and Advanced Control, 101572K (1 November 2016); https://doi.org/10.1117/12.2246928

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