"1"-shaped acoustic cascaded resonator enhanced light-induced thermoelastic spectroscopy gas sensing

In this work, a novel "1"-shaped acoustic cascaded resonator enhanced light-induced thermoelastic spectroscopy (LITES) gas sensing system is proposed for the first time, to the best of our knowledge. The designed resonator consists of three one-dimensional acoustic tubes, enabling cascaded amplification and efficient accumulation of acoustic energy in the LITES system. Finite element analysis (FEA) was employed to investigate the acoustic field distribution and optimize the key geometric parameters. Acetylene (C₂H₂) was selected as the target gas for validation. Compared with a conventional bare quartz tuning fork (QTF)-based LITES system, the proposed configuration achieved a 14.05-fold enhancement in the signal amplitude, and a minimum detection limit (MDL) of 3.1 ppm was obtained. Furthermore, the MDL was improved to 405 ppb at an average time of 200 s using Allan deviation analysis. The results demonstrate that the proposed multi-stage acoustic resonance strategy significantly enhances LITES performance and shows great potential for trace gas detection.