Cover story: Wang RQ, Qiao SD, He Y et al. Highly sensitive laser spectroscopy sensing based on a novel four-prong quartz tuning fork. Opto-Electron Adv 8, 240275 (2025).

In quartz-enhanced photoacoustic spectroscopy (QEPAS) and light-induced thermoelastic spectroscopy (LITES), the standard quartz tuning fork (QTF) with a resonance frequency of 32.768 kHz is typically used as a detector. However, the high resonance frequency, short energy accumulation time, and narrow prong gap of the standard QTF limit the performance of QEPAS and LITES systems. Recently, Professor Ma’s team at Harbin Institute of Technology reported a novel four-prong quartz tuning fork (QTF) with enlarged deformation area, large prong gap and low resonant frequency to improve its performance in laser spectroscopy sensing. A theoretical simulation model was established to optimize the design of the QTF structure. Experimental results indicated that the C2H2-QEPAS system based on this innovative design improved the signal-to-noise-ratio (SNR) by 4.67 times compared with the standard QTF-based system, and the SNR could increase up to 147.72 times when the four-prong QTF was equipped with its optimal acoustic micro-resonator (AmR). When the average time of the system reached 370 s, the system achieved a MDL as low as 21 ppb. The four-prong QTF-based C2H2-LITES system exhibited a SNR improvement by a factor of 4.52, and a MDL of 96 ppb was obtained when the average time of the system reached 100 s. The theoretical and experimental results effectively demonstrated the superiority of the four-prong QTF in the field of laser spectroscopy sensing.