Parabolic mirror cavity-enhanced Raman spectroscopy for trace gas detection.

A parabolic mirror cavity-enhanced Raman spectroscopy (PM-CERS) method was reported, utilizing a combined optical path of a parabolic mirror and a multi-pass cell. In this setup, the focal point of the parabolic mirror is aligned with the laser convergence center of the multi-pass cell. This method achieved high excitation intensity at the focal point and broadened the collection range of Raman scattering signals, thus significantly improving both the excitation and collection efficiency of Raman signals. Additionally, the structure of the system was simplified through the integrated design of the collection cavity and sample cell. Nitrogen, oxygen, water vapor, and carbon dioxide could be detected in the air within an exposure time of just 0.5 s, achieving the limits of detection at the ppm level. Compared to the conventional multi-pass cell, the signal intensity and signal-to-noise ratio were each enhanced by approximately 5.6-fold, further demonstrating the excellent potential application in trace gas detection.