All-Optical Photoacoustic Spectroscopy-Based Dual-Component Greenhouse Gas Analyzer
Min Guo, Mengda Zhou, Beilei Yang, Xinyu Zhao, Chenxi Li, Qing Yu, Guangyin Zhang, Zebo Fang, Ke Chen
Abstract
To achieve high sensitivity detection of dual-component greenhouse gases carbon dioxide and methane simultaneously, a multimechanism synergistic enhanced all-optical photoacoustic spectroscopy gas analyzer is presented. The acoustic resonance of the photoacoustic cell and the mechanical resonance of a fiber-optic cantilever acoustic sensor are used to enhance the photoacoustic signals of the dual-component gas. The optimized multipass beam reflection structure enhances the effective excitation power of the dual-component gas. The highly sensitive detection of carbon dioxide and methane at dual-frequency operating points is realized by dual-channel laser modulation combined with dual-input digital lock-in amplification technology. The Allan–Werle deviation analysis results show that with a 100 s average time, the minimum detection limits of carbon dioxide and methane are 76.5 and 1.9 ppb, respectively. The corresponding normalized noise equivalent absorption (NNEA) coefficients are 3.1 × 10 –10 and 2.9 × 10 –10 cm –1 W/Hz 1/2, respectively.