为了优化气体受激拉曼散射系统, 采用理论与实验相结合的方法, 对气体受激拉曼散射现象进行了研究。根据受激拉曼基本理论计算了CH4和D2在不同气压下的拉曼增益系数, 然后采用输出能量为70 mJ的Nd∶YAG三倍频355 nm激光进行了受激拉曼散射实验, 测量了在拉曼池气体气压为1×105~2×106 Pa, 焦距分别为500, 750 mm下的斯托克斯光的输出能量。发现CH4拉曼增益系数随气体压力升高而增大; D2拉曼增益系数在1×106 Pa左右达到最大值, 之后不随气压升高而改变。实验结果表明, 在气体受激拉曼装置中, 合理选择拉曼池气体气压和耦合聚焦透镜的焦距, 即甲烷气体系统选择长焦距高气压, 氘气系统选择长焦距低气压。理论计算与实验结果基本一致, 此研究对NO2差分吸收激光雷达光源系统的优化有着很重要的作用。

To optimize a gas-stimulated Raman scattering system, the phenomenon of gas-stimulated Raman scattering was demonstrated through a combination of theory and experiments. The Raman gain coefficients of CH4 and D2 at different pressures were calculated theoretically. Stimulated Raman scattering experiments were then conducted using a 355 nm Nd∶YAG laser with an output energy of 70 mJ. The output energies of Stokes light at gas pressures of 1×105 and 2×106 Pa and focal lengths of 500 and 750 mm were measured. It is found that the CH4 Raman gain coefficient increases with an increase in gas pressure. In addition, the D2 Raman gain coefficient reaches the maximum at approximately 1×106 Pa and then do not change with increase in gas pressure. Experimental results indicate that reasonable values for Raman cell gas pressure and focal length of the coupled focusing lens must be selected for gas-stimulated Raman device applications. For example, a longer focal length and a higher pressure must be used for a methane gas system, whereas a longer focal length and lower pressure must be used for a helium system. The theoretical calculations corresponded with the experimental results. These research results shall play a major role in optimizing the light source of NO2 differential absorption laser radar.