Abstract
A novel quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor based on a micro quartz tuning fork (QTF) is reported. As a photoacoustic transducer, a novel micro QTF was 3.7 times smaller than the usually used standard QTF, resulting in a gas sampling volume of ~0.1 mm3. As a proof of concept, water vapor in the air was detected by using 1.39 μm distributed feedback (DFB) laser. A detailed analysis of the performance of a QEPAS sensor based on the micro QTF was performed by detecting atmosphere H2O. The laser focus position and the laser modulation depth were optimized to improve the QEPAS excitation efficiency. A pair of acoustic micro resonators (AmRs) was assembled with the micro QTF in an on-beam configuration to enhance the photoacoustic signal. The AmRs geometry was optimized to amplify the acoustic resonance. With a 1 s integration time, a normalized noise equivalent absorption coefficient (NNEA) of 1.97 × 10−8 W·cm−1·Hz−1/2 was achieved when detecting H2O at less than 1 atm.
Highlights
Trace gas sensing technology has been widely used in many fields including industrial processes control, medical diagnosis, environmental monitoring, detection of toxic gases, and breath analysis [1,2,3,4].Non-optical techniques based on chemical sensing, gas chromatography/mass spectrometry., and electrochemistry have a high cost, a bulky structure, and a slow reaction rate
The quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor performance based on a bare micro quartz tuning fork (QTF) and an on-beam configuration were of 0.7 mm and 0.6 mm were selected
The QEPAS sensor performance based on a bare micro QTF and an on-beam configuration were compared
Summary
Trace gas sensing technology has been widely used in many fields including industrial processes control, medical diagnosis, environmental monitoring, detection of toxic gases, and breath analysis [1,2,3,4].Non-optical techniques based on chemical sensing, gas chromatography/mass spectrometry., and electrochemistry have a high cost, a bulky structure, and a slow reaction rate. Trace gas sensing technology has been widely used in many fields including industrial processes control, medical diagnosis, environmental monitoring, detection of toxic gases, and breath analysis [1,2,3,4]. The PAS characteristics is that the acoustic transducer is not limited by the optical wavelength by the excitation sources, which leads to the fact that a commonly used microphone can be applied to from ultraviolet to infrared light sources [12]. This fact makes the PAS applications more wide-ranging and reduces the cost of PAS based instruments. PAS has been used to monitor nitric oxide (NO) in vehicle exhaust emissions [14] and methane (CH4 ) in atmospheric pollution [15]
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