Detection of Trace Sulfur Dioxide Gas Using Quartz-Enhanced Photoacoustic Spectroscopy

By combining the wavelength demodulation and second harmonics, the trace H2S gas is detected based on the quartz-enhanced photoacoustic spectroscopy (QEPAS). A distributed feedback semiconductor laser with an output wavelength of 1578 nm is used as the excitation source. Furthermore, a finite element analysis method is used in the simulation calculation for a quartz tuning fork, typically used in QEPAS systems, to obtain its first six modes and resonance frequencies. In an experiment, an acoustic micro-resonator with a length of 1 mm and an inner diameter of 0.7 mm is added, and a transimpedance amplifying circuit is optimized to detect the H2S gas under optimal experimental conditions. The results denote that the second harmonic signal of the QEPAS system exhibits a strongly linear relation with the H2S gas concentration, and a detection limit of 19.3 X 10(-6) is obtained.