Cover story: Sun HY, He Y, Qiao SD et al. Highly sensitive and real-simultaneous CH₄/C₂H₂ dual-gas LITES sensor based on Lissajous pattern multipass cell. Opto-Electron Sci 3, 240013 (2024).

Trace gases are atmospheric constituents with a volume fraction of less than 1%. Despite their low concentrations, nitrogen oxides, hydrocarbons, and sulfides in the atmosphere have a significant impact on the environment, closely related to phenomena such as acid rain, greenhouse effects, and ozone layer depletion. Therefore, race gas detection is crucial for environmental protection. In addition, it has important research and application values in fields such as industry, medicine, and fire warning.

Light-induced thermoelectric spectroscopy (LITES) quickly became a research focus due to its high sensitivity, fast response, and noncontact full-band spectrum detection capabilities. How to further improve the sensitivity, response speed and integration of LITES sensor system will be the focus of subsequent research. By extending the propagation path of laser in gas, the detection sensitivity of LITES sensor can be effectively improved. Therefore, developing new optical multi-pass cells (MPC) is crucial for achieving higher performance LITES sensors.

In dual-gas simultaneous detection technologies, time-division multiplexed (TDM) is difficult to achieve fast response and suit volatile environments. As for frequency-division multiplexed (FDM), it is unsuitable for sensor system with resonance frequency. To address these issues, a highly sensitive and real-simultaneous CH4/C2H2 dual-gas LITES sensor based on a novel Lissajous pattern multi-pass cell and trapezoidal-head QTF was presented by the team of Prof. Ma from Harbin Institute of Technology. It provides an effective reference value for the subsequent development of LITES sensing technology.