A quartz enhanced photoacoustic spectroscopy (QEPAS) sensor, employing an erbium-doped fiber amplified laser source and a custom quartz tuning fork (QTF) with its two prongs spaced ∼800 μm apart, is reported. The sensor employs an acoustic micro-resonator (AmR) which is assembled in an “on-beam” QEPAS configuration. Both length and vertical position of the AmR are optimized in terms of signal-to-noise ratio, significantly improving the QEPAS detection sensitivity by a factor of ∼40, compared to the case of a sensor using a bare custom QTF. The fiber-amplifier-enhanced QEPAS sensor is applied to H₂S trace gas detection, reaching a sensitivity of ∼890 ppb at 1 s integration time, similar to those obtained with a power-enhanced QEPAS sensor equipped with a standard QTF, but with the advantages of easy optical alignment, simple installation, and long-term stability.

Quartz-enhanced photoacoustic spectroscopy (QEPAS) with a single-tube acoustic microresonator (AmR) inserted between the prongs of a custom quartz tuning fork (QTF) was developed, investigated, and optimized experimentally. Due to the high acoustic coupling efficiency between the AmR and the QTF, the single-tube on-beam QEPAS spectrophone configuration improves the detection sensitivity by 2 orders of magnitude compared to a bare QTF. This approach significantly reduces the spectrophone size with respect to the traditional on-beam spectrophone configuration, thereby facilitating the laser beam alignment. A 1σ normalized noise equivalent absorption coefficient of $1.21\times {10}^{-8}{\mathrm{cm}}^{-1}·\mathrm{W}/\sqrt{\mathrm{Hz}}$ was obtained for dry ${\mathrm{CO}}_2$ detection at normal atmospheric pressure.