Fast step heterodyne light-induced thermoelastic spectroscopy gas sensing based on a quartz tuning fork with high-frequency of 100 kHz

In this paper, a fast step heterodyne light-induced thermoelastic spectroscopy (SH-LITES) sensor using a high-frequency quartz tuning fork (QTF) with resonant frequency of ~100 kHz is reported for the first time. The theoretical principle of heterodyne LITES (H-LITES) signal generation is analyzed firstly, and an acetylene (C2H2) H-LITES sensor is established to verify its performance. Experimental comparisons between the high-frequency QTF and a standard commercial QTF with resonant frequency of ~32.768 kHz reveal that the high-frequency QTF exhibits a tenfold faster response time. Specifically, the H-LITES sensor with this QTF achieves a 33 ms measurement cycle, 90% shorter than commercial counterparts.…