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

Application of piezoelectric transducers in photoacoustic spectroscopy for trace gas analysis

“…High-Q quartz crystals are employed as a frequency standard in clock, watches, and smart phones. Generally, standard QTFs have a resonance frequency of 32.7 kHz ($2 15 Hz). The U-shaped standard QTF prong dimensions of 3.2 mm (l) × 0.33 mm (w)× 0.4 mm (t) and the QTF prong spacing of $0.3 mm is widely used which is showed in Figure 2.…”

“…The configuration was used to detect water vapor at 1368.597 nm, achieving the detection limit of 166 ppb. 15 An off-beam (OB) QEPAS spectrophone configuration was theoretically and experimentally investigated by Liu, K. and Yi, H. [16][17][18] In the OB-QEPAS spectrophone shown in Figure 5, the laser beam is directed through a novel AmR with a slit in the middle. The QTF is placed adjacent to the AmR as close as possible.…”

“…A QEPAS spectrophone with three AmRs was designed in by Wang et al 15 In the PA cell, three AmRs and a fiber reflector were combined to enhance the PA signal. The configuration included three AmRs arranged on both sides of QTF vertically along the QTF prong at 45 degree.…”

“…A fiber reflector was used to improve the laser intensity by reflecting the laser to pass through the QTF twice along the designed light path. The configuration was used to detect water vapor at 1368.597 nm, achieving the detection limit of 166 ppb 15 …”

Quartz-Enhanced Photoacoustic Spectroscopy for Four-Component Gas Detection Based on Two Off-Beam Acoustic Microresonators

“…A NNEA of 1.21 × 10 -8 cm −1 W Hz -1/2 was then obtained for carbon dioxide (CO 2 ) detection [11]. Wang et al proposed an on-beam structure that was based on three AMRs to improve the acoustic signal and obtained an MDL of 166 ppbv for water vapor (H 2 O) [12]. Liu et al optimized the off-beam AMR to realize superior detection performance and a NNEA of 6.2 × 10 -9 cm −1 W Hz -1/2 was obtained for H 2 O detection [13].…”