Miniature Quartz Tuning Fork-Based Light-Induced Thermoelastic Spectroscopy Sensing

Light-induced thermoelastic spectroscopy (LITES), boasting an extended effective optical path length, stands as a potent approach for trace gas detection. The indispensable factor for heightened measurement sensitivity lies in the quartz tuning fork (QTF) probe, possessing a robust thermoelastic conversion efficiency. In this study, we introduce a novel laser micromachining technique for fabricating sensitive miniature QTFs (mQTFs) tailored to suit LITES applications. This innovation effectively addresses the issues of subpar sensitivity and the elevated laser response threshold commonly observed in commercial QTFs. As a proof of concept, we demonstrate its capabilities through the measurement of CO2. Capitalizing on the utilization of mQTFs, the sensing sensitivity was increased by an impressive factor of ~5, outperforming the conventional QTF-LITES approach. The minimum detection limits (MDLs) for CO2 are also notably improved, measuring 351.34 ppm for the mQTF and 968.29 ppm for the standard commercial QTF. This cost-effective technological advancement paves the way for the development of highly responsive trace gas LITES sensing systems.