Eccentrically Connected and Dual-Enhanced Microwhistle Fiber Film Photoacoustic Spectroscopy Sensor for Trace Gas Detection

Conventional T-type photoacoustic cells are hindered by laser-induced noise from direct microphone exposure to the pump laser, negatively impacting the sensor’s detection threshold. To address this, a novel micro-whistle fiber film photoacoustic spectroscopy (MWFF-PAS) sensor has been developed, integrating a micro-whistle resonant photoacoustic cell (MWR-PAC) with a fiber film microphone in an eccentric configuration. The MWR-PAC comprises a cone-curved buffer chamber and a disc resonant cavity, mimicking the acoustic generation mechanism of a whistle, which enhances the quality factor and concentrates resonance-amplified photoacoustic signals at the cavity’s edge. The eccentric placement of the fiber film microphone optimally captures these peak signals while minimizing direct laser exposure to the metallic film, thereby reducing background noise and improving the detection threshold. Experimental results with acetylene gas reveal a minimum detection limit of 5.78 ppb, with an integration time of 258 s, corresponding to a normalized noise equivalent absorption coefficient of 7.14×10⁻⁹ W·cm⁻¹·Hz⁻¹/². The MWFF-PAS sensor boasts a compact design and ppb-level detection limit, effectively mitigating pump laser interference and advancing the miniaturization of all-optical resonant photoacoustic gas detection technology.