Methane gas detection based on cavity-enhanced Raman spectroscopy

Abstract To achieve efficient and accurate detection of methane gas, this study proposes a Raman spectroscopy detection method based on near-concentric cavity enhancement. Through theoretical simulation and optical optimization, a near-concentric cavity structure with matched radii of curvature was designed, enabling the laser to form a stable standing wave mode inside the cavity and achieve over 100 effective reflections. This enhances the Raman signal intensity by 127 times compared to single-pass detection. Experimental results show that under normal temperature and pressure, the device can clearly identify two Raman characteristic peaks of methane at 2719 cm −1 and 3020 cm −1 ; with an integration time of 60 s, the limit of detection (LOD) for methane is as low as 0.62 ppm; the intensity of methane’s characteristic peaks exhibits a high linear correlation with integration time, laser power, and intracavity pressure (R 2 > 0.997); a concentration standard curve was established, and using 504 ppm methane as the verification concentration, the results indicate that the quantitative accuracy of the device for methane reaches 99.65%. These findings confirm that the method has excellent sensitivity and accuracy, meets the requirements for precise methane gas detection, and provides a promising solution for the field of greenhouse gas analysis.