用CARS技术确定拉曼退偏比的一种数据处理新方法

Yuika等人利用偏振CARS技术可以准确地确定分子的拉曼退偏比.其方法是，首先对不同检偏角_d所对应CARS谱峰的频率分布进行数学模拟，然后由所得系数随检偏角φ_d的变化求得使CARS信号中共振项消失的偏振角φ^０_d，最后由消失条件ρ＝-1/(tanθtanφ⁰_d)求出退偏比ρ，θ为产生CARS光的Pump光与Stokes光偏振方向的夹角.本文提出的数据处理方法，即交点法.同Yuika等人处理数据的方法相比，交点法毋需关于谱峰频率分布的知识，做法也更为简便.

New treatment of CARS spectrum to determine the Raman depolarization ratio

The Raman depolarization ratio ρ can be determined accurately by polarization-resolved coherent anti-stokes scattering (CARS) technique (J. Raman Spectrosc., 2000, 31: 725). The polarized CARS spectra are recorded at a series of polarization angles φ_d, and simulated by a Lorentz bandshape to obtain signal amplitude H_R of the resonant part. From the dependence of H_R on polarization angle φ_d, the angle φ⁰_d corresponding to H_R=0 can be determined. So the Raman depolarization ratio can be obtained from the relationship ρ＝-1/(tanθtanφ⁰_d), where θ is the polarization angle between Pump beam and Stokes beam. In this report, we introduce another method to process the data from polarized CARS spectrum, namely the method of intersecting point. Compared with the original method, our method needs not any knowledge of frequency distribution of the CARS spectrum, and is simpler.