Optical field modulation-enhanced cantilever sensor-based photoacoustic spectroscopy gas detection system

This study presents an approach to enhance the sensitivity of cantilever sensor-based photoacoustic (PA) spectroscopy gas detection systems through optical field modulation. Theoretical investigations into the mechanism and method of optical field modulation are followed by experimental validation. Acetylene is selected as the target molecule, with a near-infrared DFB LD laser serving as the light source. A dual-lens configuration was constructed to yield a better optical field distribution compared to the single-lens configuration. In the near-field of the laser, the setup of the dual-lens configuration has a better sensitivity than that of the single-lens setup, with a limit of detection reaching 0.52 μl l⁻¹. In the far-field of the laser, however, the PA signals are significantly lower than that of near-field measurements, indicating that far-field measurement is not preferred. The results can provide references to the sensitivity improvement of the PA spectroscopy-based gas sensing system.