Near-infrared laser photoacoustic gas sensor for simultaneous detection of CO and H₂S

Abstract

A ppb-level H₂S and CO photoacoustic spectroscopy (PAS) gas sensor was developed by using a two-stage commercial optical fiber amplifier with a full output power of 10 W. Two near-infrared diode lasers with the central wavenumbers of 6320.6 cm^-1 and 6377.4 cm^-1 were employed as the excitation laser source. A time-division multiplexing method was used to simultaneously detect CO and H₂S with an optical switch. A dual-resonator structural photoacoustic cell (PAC) was theoretically simulated and designed with a finite element analysis. A µV level background noise was achieved with the differential and symmetrical PAC. The performance of the multi-component sensor was evaluated after the optimization of frequency, pressure and modulation depth. The minimum detection limits of 31.7 ppb and 342.7 ppb were obtained for H₂S and CO at atmospheric pressure.