A Multiexcitation Type Dual-Spectroscopy Gas Sensor Based on Dual Quartz Tuning Forks

This study reports an innovative dual-spectroscopy integrated detection system that combines quartz-enhanced photoacoustic spectroscopy (QEPAS) and laser-induced thermoelectric spectroscopy (LITES), utilizing dual-quartz tuning forks (QTFs) to achieve highly sensitive gas detection. An off-axis acoustic microresonator (AMR) was placed laterally to each QTF, arranged in parallel vertically. Each QTF detected dual QEPAS signals from the AMR tube. The laser beam sequentially passed through two off-axis AMRs and was incident at an angle between the QTFs, where it underwent multiple reflections to achieve repeated LITES signal excitation. Ultimately, this configuration generated four QEPAS signals and three LITES signals with a single laser beam. To enhanced overall signal strength, the outputs of QTF1 and QTF2 were combined via an adder. The sensor system was evaluated using acetylene (C2H2) as the target gas, achieving a minimum detection limit (MDL) of 1.06 ppm, demonstrating its effectiveness in gas detection.