Two-Component Gas Sensor of Time-Division Multiplexing Technique Based on QEPAS and LITES

A two-component gas sensor based on Quartz-Enhanced Photoacoustic Spectroscopy (QEPAS) and Light-Induced Thermoelastic Spectroscopy (LITES) was realized by the time-division multiplexing technique. Two off-beam acoustic microresonator (AMRs) were used in the experiment for twice excitation and enhancement of QEPAS signal. The four fiber collimators were connected with the two off-beam AMRs to be responsible for laser propagation in the two AMRs. After passing through the second AMR, the laser beam was incident to the sidewall of the quartz tuning fork (QTF) by the fiber collimator 5 for the excitation of the LITES signal, which realized the superposition of QEPAS signals and LITES signal on a single QTF. The time-division operation of distributed feedback lasers was realized by optical switches to accomplish the detection of C2H2 and CH4. The experimental results showed that the minimum detection limits of C2H2 and CH4 were 2.06 ppmv and 7.14 ppmv, respectively, which proved that the gas sensor had good sensing performance.