Elimination of Laser Power Loss Influence for Multi-Point Gas Sensing in Photoacoustic Spectroscopy

In this paper, we propose a scheme to eliminate the laser power losses that occur in photoacoustic spectroscopy (PAS) multi-point gas sensing that uses a reference gas channel, and we then design a new two-optical-path PAS gas cell that is constructed using both sensing and reference gas cells. The second harmonic PAS signals are extracted from the sensing and reference gas cells using a lock-in amplifier, and the ratio of these signals is used to calculate the gas concentration in an approach that can effectively eliminate the influence of laser power losses on the system's detection performance. Acetylene (C
₂
H
₂
)gas is detected at 1532.83 nm in multi-point PAS experiments and the effectiveness of the proposed loss elimination scheme is verified. Using three new two-optical-path PAS gas detection devices, the linear responses of the proposed sensor to the acetylene concentration are determined, with yielded R-square values of 0.99834, 0.99788, and 0.99603 being obtained.