Compact TDLAS methane sensor based on a triple-switching matrix multipass cell

High-precision detection of methane is highly valuable in many fields, such as natural gas pipeline leakage detection, greenhouse gas monitoring, and noninvasive disease diagnosis. However, significant technical challenges remain in further improving the sensitivity and portability of methane sensors. Multipass cells (MPCs) adopted in existing sensors based on tunable diode laser absorption spectroscopy (TDLAS) generally suffer from limited optical path length and poor beam quality under the constraint of a small volume, which restricts the overall detection performance of the sensors. To address the above technical difficulties, in this study, a high-precision methane sensor based on a novel multipass cell named the triple-switching matrix multipass cell (TSMC) was designed and developed. The TSMC can realize triple switching of the reflection mode of the Pickett Bradley White Cell (PBWC) in three directions and has the remarkable advantages of excellent beam quality, a high ratio of optical path length to volume (RLV), and separation of incident and exit positions. The experimental results reveal that the TSMC can achieve an effective optical path length of 53.2 m with an effective optical volume of only 268.27 mL, and the RLV reaches 19.83 cm − 2 , demonstrating excellent miniaturization potential. Allan deviation analysis indicates that the sensor has a minimum detection limit of 12.6 ppb at an average time of 9.4 s, indicating high detection sensitivity. The sensor design proposed in this study provides a new approach for improving the high-precision detection of trace gases.