受激旋转拉曼散射效应对基频光光束质量的影响

Effects of stimulated rotational Raman scattering on beam quality of fundamental frequency beams

采用瞬态受激旋转拉曼散射(SRRS)和空间相位扰动模型,定量分析了泵浦光强度和脉冲宽度对基频光在空气长程传输过程中产生的SRRS效应的阈值距离和转换效率的影响,讨论了泵浦光空间相位畸变对长程传输后的基频光光束质量的影响。研究结果表明:SRRS效应的阈值距离随着泵浦光强度和脉宽的增大而变短;空间相位畸变对斯托克斯光和泵浦光的光强分布存在一定影响,对斯托克斯光相位分布的影响比对泵浦光相位的影响大;SRRS效应的存在将导致基频光光束质量明显变差,对谐波转换效率产生明显影响。

Based on the model of transient stimulated rotational Raman scattering（SRRS） and the phase perturbation theory, the effects of pump intensity and pulse width on the threshold and the conversion efficiency of SRRS during the propagation in long air path were quantitatively analyzed. The effects of the phase perturbation on the beam quality of the pump field and the Stokes field were discussed. The results show that the threshold distance of SRRS decreases with increasing the intensity and the pulse width of the pump laser. The phase perturbation of the initial pump field has effect on the intensity distributions of the Stokes and the pump fields, and the influence of the phase perturbation of the initial pump field on the Stokes field is more obvious than that on the pump field. The SRRS effect can lead to the degradation of the beam quality of the Stokes field and the pump field, resulting in the reduction of the conversion efficiency of the harmonic generation process.