Trace Gas Detection System Based on All-Optical Quartz-Enhanced Photoacoustic Spectroscopy. Issue 11 (November 2019)

• Record Type: Journal Article
• Authors: Lin, Cheng; Liao, Yu; Fang, Fei
• Is Part Of: Applied spectroscopy. Volume 73:Issue 11(2019)
• Page Start: 1327
• Page End: 1333
• Publication Date: 2019-11
• Subjects: All optical -- quartz-enhanced photoacoustic spectroscopy -- QEPAS -- self-stabilization -- Fabry–Perot interferometric sensor; Spectrum analysis -- Periodicals; 543.505
• DOI: 10.1177/0003702819866468
• Languages: English
• ISSNs: 0003-7028

Abstract

An all-optical quartz-enhanced photoacoustic spectroscopy system (QEPAS) with quadrature point stabilization for trace gas detection was reported. The extrinsic interferometry-based optical fiber Fabry–Perot sensor with quadrature point self-stabilization for detection of quartz prong vibration was used to replace the conventional one. The optimal coefficient of the modulation depth was ∼2.2 theoretically and experimentally, corresponding to the modulation depth of ∼0.1795 cm −1 at an acetylene (C2 H2 ) absorption line of 6534.36 cm −1 . Furthermore, the enhancement of QEPAS signal was obtained by using different microresonators. The minimum detectable limit of ∼580 parts per billion by volume (ppbv) was obtained. A normalized noise equivalent absorption coefficient for C2 H2 of 2.95 × 10 −7 cm −1 ·W·Hz –1/2 was obtained. The detection sensitivity was enhanced by a factor of ∼2.1 in comparison to the conventional QEPAS system. The linear correlation coefficient of the QEPAS signal response to the C2 H2 concentration was 0.998 within the range from 10 parts per million by volume (ppmv) to 500 ppmv. Finally, the long-term stability of the QEPAS system was evaluated using Allan deviation analysis, and the ultimate detection limit of ∼130 ppbv was reached for an optimum averaging time of ∼108 s at atmospheric pressure and ambient temperature.