多色宽带相干反斯托克斯拉曼散射过程的理论与实验研究

Theoretical and experimental study on the multi-color broadband coherent anti-Stokes Raman scattering processes

宽带相干反斯托克斯拉曼散射(coherent anti-Stokes Raman scattering,CARS)光谱技术能够同时获取完整的分子CARS光谱信息,以准确识别和定量分析混合物中的不同成分或未知成分.在宽带CARS光谱技术中,由于超连续谱激光有效光谱范围内各光谱成分的作用不同,分别会产生双色和三色CARS过程.这里我们在理论上分析了宽带激发条件下两种CARS过程的产生条件,以及不同CARS光谱信号强度与各激发光功率之间的关系.在此基础上,搭建了基于SC激光的宽带CARS光谱系统,分别实现了双色和三色CARS过程.通过对获得的苯甲腈样品的CARS光谱信号进行函数拟合分析,实验验证了上述两个过程中CARS信号的强度与各激发光强度之间的函数关系.理论和实验研究结果为进一步优化宽带时间分辨CARS光谱探测和显微系统,实现同时获取物质分子完整的CARS光谱信号提供了指导.

In order to exactly distinguish and quantitatively analyze the different or unknown components in a mixture, the global molecular CARS spectra information should be obtained simultaneously with a broad-band coherent anti-Stokes Raman scattering （CARS） spectroscopy in supercontinuum. In a broad-band CARS spectroscopy, two-and three-color CARS processes are generated due to different functions of effective spectroscopic components in supercontinuum. Firstly, we theoretically analyzed the generation conditions of CARS signals and the relationships between their intensity and power of excitation lights in the two types of CARS process with the broad-band excitation. On this basis, the two types of CARS process are achieved with a home-built broad-band CARS spectroscopic system, respectively. Using the functional fitting analysis of the obtained CARS spectral signals of benzonitrile, the relationships between CARS signals and excitation lights are experimentally verified in two different kinds of CARS process. Further optimizations of broad-band time-resolved CARS spectroscopic and microscopic systems, for simultaneously obtaining the global CARS spectral signals of samples, can be achieved under the guidance of theoretical and experimental results.