Research Progress and Trend of Gas Raman Sensing Enhancement Technology

Whether in scientific research, food safety, medical testing, or in the fields of safety accident prevention, fast, accurate, qualitative and quantitative analysis of multi-component mixed gases has become an urgent need. Raman spectroscopy is a powerful gas sensing method. It can overcome the shortcomings of traditional non-spectroscopic methods, such as long detection time and poor repeatability, and it can also make up for the shortcoming of absorption spectroscopy that cannot directly measure homonuclear diatomic molecules. A single-frequency laser can be used for qualitative and quantitative analysis of multi-component mixed gases. However, due to the inherently weak Raman effect of matter, and the Raman effect of the gas is generally much lower than that of solid and liquid, this greatly limits the wider application of Raman spectroscopy in gas sensing. Improving the scattering intensity of gas is key to making gas Raman sensing technology more widely used. Currently, the most important gas Raman sensing enhancement technology includes cavity enhancement technology and optical fiber enhancement technology. Cavity enhancement technology enhances the Raman scattering signal from the source by increasing the intensity and path of the excitation light that interacts with the gas to be measured, including multiple pass cavity enhancement, F-P cavity enhancement, and laser cavity enhancement. Fiber enhancement, including silver-plated capillary tube enhancement and hollow fiber enhancement, enhances the Raman scattering signal by improving the collection efficiency of spherical scattered light so that most of the Raman scattered light can enter the spectral detector. This paper briefly introduces the enhancement principles of the above two technologies, summarizes the research progress and application status, and discusses their advantages and limitations. Finally, focusing on detecting multi-component trace gases, it looks forward to the future development trend of gas Raman sensing technology. Although the current spectrum analysis method based on the absorption effect dominates the field of gas detection, especially photoacoustic spectroscopy, shortly, gas Raman sensing technology is expected to be more extensive and in-depth in the field of gas detection.