Parabolic mirror-based cavity-enhanced Raman spectroscopy gas detection system

Raman spectroscopy is widely utilized in multi-component gas detection due to its rapid detection, good repeatability, and low cross-interference. However, the inherently low Raman scattering cross-section of gases results in exceedingly weak Raman signals, which impedes the further advancement of Raman spectroscopy gas detection. The multi-pass cavity-enhanced Raman spectroscopy technique can improve the excitation efficiency of Raman signals by converging the laser through multiple reflections to a focal point. Nonetheless, the employment of lenses to capture Raman signals at the convergence point results in limited collection efficiency. To address this challenge, Parabolic Mirror Cavity-Enhanced Raman Spectroscopy (PMCERS) is proposed aimed at concurrently enhancing the excitation and collection efficiency of Raman signal light. A parabolic mirror collection cavity is introduced to precisely couple the focal point of the parabolic mirror with the central convergence point of the multi-pass cavity, thereby collimating the Raman signal light at the focal point into parallel light emission. To enable efficient collimation of signal light emissions while preserving the integrity of signal collection efficiency, an annular reflector was integrated with the parabolic mirror. Through the analysis of the angles at which light rays were emitted from the focal point, the ideal dimensions of the annular reflector were ascertained. To verify the effectiveness of the PMCERS, comparative experiments demonstrated that, compared to traditional near-concentric cavity, PMCERS increased the Raman signal intensity detected in air by five times. In all, PMCERS enhanced both signal excitation and collection efficiency while simplifying the system structure, providing an efficient and stable solution for multi-component gas detection.