Photoacoustic Spectroscopy Based Methane Sensor Using a Double-Pass Photoacoustic Cell
YANG Yan-fang1, 2, PEI Kai-long1, 2, YIN Xu-kun1, 2, WU Hong-peng1, 2, LI Shang-zhi1, 2, CUI Ru-yue1, 2, MA Wei-guang1, 2, ZHANG Lei1, 2, YIN Wang-bao1, 2, DONG Lei1, 2*, JIA Suo-tang1, 2
1. State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Shanxi University, Taiyuan 030006, China
2. Collaborative Innovation Center of Extreme Optics, Taiyuan 030006, China
Abstract：A laser based Photoacoustic sensor system was demonstrated and developed for methane (CH4) detection using a custom double-pass photoacoustic cell with a large inner diameter. The sensor used a butterfly-package distributed feedback (DFB) laser with its wavelength targeting the CH4 absorption line at 6 046.96 cm-1. A high-reflection plane mirror was positioned behind the photoacoustic cell to enhance the absorption optical path and improve the detection sensitivity. The sensor parameters including the modulation frequency, modulation depth of the laser and gas flow were optimized. Under theatmospheric pressure, the novel CH4 sensor showed a detection sensitivity of 0.21 ppm with a 1 s averaging time, which corresponded to a 1σ normalized noise equivalent absorption (NNEA) of 2.1×10-8 cm-1·W·Hz-1/2. The excellent performance of this CH4 sensor promises broad applicability to industry, mine, medical and environmental monitoring, etc.
