Scattering enhanced photoacoustic gas sensor based on acetate membrane

In this paper, a scattering enhanced photoacoustic spectroscopy (SEPAS) technique is introduced for trace gas detection. An acetate membrane is mounted at the inner wall of a miniaturized photoacoustic (PA) cell to improve the light-gas interaction path. It has been found out from theoretical simulations that the light rays in the PA cell with the acetate material are obviously denser, leading to a large enhancement of the PA signal. A SEPAS system, mainly consisting of a PA sensor, a near-infrared distributed feedback laser source, and a high-speed demodulator has been developed for CH4 detection. The experimental results have successfully proved that the SEPAS technique based on the porous acetate material can achieve at least three times enhancement on the PA signal, compared with the PA cell without the acetate membrane. The minimum detection limit is calculated to be 57.5 parts per billion with an averaging time of 100 s.