A grooved quartz tuning fork (QTF) with a prong spacing of 800 µm for QEPAS application is reported. The prongs spacing is large enough to facilitate optical alignments when a degraded laser beam is used for QEPAS-based trace gas sensors. The grooved QTF has a resonance frequency of 15.2 kHz at atmospheric pressure and is characterized by four rectangular grooves carved on the QTF prong surfaces. With a grooved-prong, the electrical resistance R of the QTF is reduced resulting in an enhanced piezoelectric signal, while the Q factor is not affected, remaining as high as 15000 at atmospheric pressure. The geometric parameters of the acoustic micro resonators (AmRs) for on-beam QEPAS were optimized to match the grooved QTF, and a signal-to-noise gain factor of ∼ 30 was obtained with an optimum configuration. The performance of the QEPAS-based sensor was demonstrated exploiting an interband cascade laser (ICL) for CH4 detection and a 1σ normalized noise equivalent absorption (NNEA) coefficient of 4.1×10−9 cm−1 W/Hz was obtained at atmospheric pressure.
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|Titolo:||Piezo-enhanced acoustic detection module for mid-infrared trace gas sensing using a grooved quartz tuning fork|
|Data di pubblicazione:||2019|
|Appare nelle tipologie:||1.1 Articolo in rivista|