Ultra-high sensitive light-induced thermoelastic spectroscopy sensor with a high Q-factor quartz tuning fork and a multipass cell.

An ultra-high sensitive light-induced thermoelastic spectroscopy (LITES) sensor based on a resonant high Q-factor quartz turning fork (QTF) and a Herriot multipass cell was demonstrated for the first time, to the best of our knowledge. The performance of LITES and widely used tunable diode laser absorption spectroscopy (TDLAS) were experimentally investigated and compared at the same conditions. Carbon monoxide (CO) was chosen as the analyte to verify the reported sensors' performance. With a minimum detection limit (MDL) of 470 ppb for 60 ms integration time and a noise equivalent absorption (NEA) coefficient of 2.0×10-7  cm-1 Hz-1/2, and a MDL of 17 ppb with an optimum integration time of 800 s, the reported LITES sensor showed a superior sensing capability compared with a TDLAS sensor and a conventional quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor.