Abstract
We demonstrate an ultrasensitive photoacoustic sensor using a low laser power (4 mW) and high-finesse () optical cavity. The Pound–Drever–Hall (PDH) method is adopted to lock the external cavity diode laser at 1531.58 nm to the Fabry–Pérot cavity. By placing a photoacoustic cell inside the 130-mm-long optical cavity, we obtain an enhancement of more than 630 times in laser power for acetylene () detection. The present photoacoustic spectroscopy (PAS) sensor achieves a normalized noise equivalent absorption coefficient of , which is unprecedented sensitivity among all the current PAS sensors. Our results demonstrate the feasibility of merging PAS with a high-finesse cavity using PDH locking for ultrasensitive trace gas detection.
© 2019 Optical Society of America
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