Optics Communications ( IF 2.2 ) Pub Date : 2021-09-08 , DOI: 10.1016/j.optcom.2021.127447 Cheng Lin 1 , Xueyang Yan 1 , Yongchao Huang 1
An all-optical off-beam quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor employing double-pass acoustic microresonators was proposed and experimentally investigated. An optical fiber Fabry–Perot interferometric sensor with quadrature point self-stabilization was employed for the detection of quartz prong vibration. A commercial quartz tuning fork with a resonant frequency of 30.72 kHz was employed as an acoustic transducer. Water vapor as the catalyst was added for improving the vibrational energy transfer. The minimum detection limit of 2.41 ppmv was obtained with a 1 s averaging time, which corresponded to a normalized noise equivalent absorption coefficient of 7.7610−8 cm−1 W Hz−1/2 at the methane absorption line of 6046.95 cm −1 with an optimized modulation depth of 0.172 cm −1. The detection sensitivity was enhanced by a factor of 1.48 in comparison to the off-beam QEPAS employing a single-pass microresonator. An Allan deviation analysis indicated that the ultimate detection limit for the QEPAS-based sensor was 0.288 ppmv at the optimum averaging time of 125 s.