Three acoustic microresonator quartz-enhanced photoacoustic spectroscopy for trace gas sensing

Abstract Quartz-enhanced photoacoustic spectroscopy (QEPAS) based on three acoustic microresonators (AmRs) of on–beam structure is developed and experimentally investigated. The three AmRs arranged two sides of the quartz tuning fork (QTF) vertically along the QTF prong exhibits a strong laser enhancement between the AmR and the QTF, which results in a 31.15 times increasement compared with the construction of the bare QTF. Six fiber collimators were placed the two ends of every AmR to collimate and collect the laser. Moreover, a fiber reflector connected into the output fiber collimator offered a 1.39 times enhancement further by increasing laser power which passing through QTF again. The configuration was investigated by the water vapour at 1368.597 nm, achieving the minimum detection limits (MDL) of 166 ppb and the excellent R-square values 0.9967 in the concentration range from 400 ppm to 2000 ppm.