High-Sensitivity Detection of Water Vapor Concentration: Optimization and Performance

详细

We demonstrate a trace gas sensor to measure the water vapor (H₂O) concentration based on quartzenhanced photoacoustic spectroscopy (QEPAS). Here, the wavelength-modulation spectroscopy (WMS) with the second-harmonic detection is utilized. We add two metallic tubes acting as a microresonator (mR) to the quartz tuning fork (QTF) sensor design to improve the sensor signal level. After optimization of the mR dimensions and laser modulation depth, we obtain a minimum detection limit (MDL) of 5.73 ppm.