Quartz-enhanced photoacoustic spectroscopic methane sensor system using a quartz tuning fork-embedded, double-pass and off-beam configuration

Lien Hu; Chuantao Zheng; Minghui Zhang; Dan Yao; Jie Zheng; Yu Zhang; Yiding Wang; Frank K Tittel

doi:10.1016/j.pacs.2020.100174

Quartz-enhanced photoacoustic spectroscopic methane sensor system using a quartz tuning fork-embedded, double-pass and off-beam configuration

Photoacoustics. 2020 Mar 10:18:100174. doi: 10.1016/j.pacs.2020.100174. eCollection 2020 Jun.

Authors

Lien Hu¹, Chuantao Zheng¹, Minghui Zhang¹, Dan Yao¹, Jie Zheng¹, Yu Zhang¹, Yiding Wang¹, Frank K Tittel²

Affiliations

¹ State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, 2699 Qianjin Street, Changchun, 130012, PR China.
² Department of Electrical and Computer Engineering, Rice University, 6100 Main Street, Houston, TX, 77005, USA.

Abstract

Development of a methane (CH₄) sensor system was reported based on a novel quartz-tuning-fork (QTF)-embedded, double-pass, off-beam quartz-enhanced photoacoustic spectroscopy (DP-OB-QEPAS). A simplified and accurate numerical model was presented to optimize the DP-OB-QEPAS spectrophone and to enhance the detection sensitivity. A compact and fiber-coupled acoustic detection module (ADM) with a volume of 3 × 2×1 cm³ and a weight of 9.7 g was fabricated. A continuous-wave distributed feedback diode laser was used to target the CH₄ absorption line at 6046.95 cm^-1. With the combination of wavelength modulation spectroscopy (WMS) and second harmonic (2f) detection technique, the CH₄ sensor system reveals a 1σ detection limit of 8.62 parts-per-million in volume (ppmv) for a 0.3 s averaging time with an optimized modulation depth of 0.26 cm^-1. The proposed CH₄ sensor shows a similar or even lower level in the normalized noise equivalent absorption coefficient (NNEA) (1.8 × 10^-8 cm^-1∙W/√Hz), compared to previously reported QEPAS-based CH₄ sensors.

Keywords: Double-pass off-beam; Methane detection; Photoacoustic spectroscopy; Quartz tuning fork; Wavelength modulation spectroscopy.