位相畸变对强紫外激光在空气中长程传输的影响

Effect of phase perturbation on high power ultraviolet laser beams in long air path

采用瞬态受激旋转拉曼散射(SRRS)模型,详细考虑了激光脉冲的位相变化、时间波形、泵浦光 的衰减、斯托克斯光的非线性放大以及初始的随机斯托克斯散射场等诸多因素,研究了空间位相畸变对空气中 长程传输过程中产生的SRRS效应的影响。研究结果表明:位相畸变对阈值条件和时间特性影响较小,而对光 束质量影响较为明显;随着位相畸变的增大,光束的能量分布变得极不均匀,光束的光强对比度也明显变大, 从而使激光光束质量变差,而且当传输距离达到阈值条件后,随着传输距离的增加,光束质量将进一步变差。

Using the model of transient stimulated rotational Raman scattering (SRRS) and considering many factors such as phase change of laser beams, the pulsed-shape, the depletion of pump laser, the nonlinear amplification of the Stokes field, and the initial random Stokes scattered field, etc, the effect of the spatial phase perturbation on the SRRS of high-power ultraviolet laser beams in long air path has been studied. It is shown that the effects on the threshold of SRRS and the temporal pulse profile are weak. However, the effect on the beam quality is very evident. It is also shown that the energy distribution of the beam becomes more non-uniform and the beam intensity contrast increases sharply as the phase perturbation grows, reducing the beam quality. When the propagation distance is beyond the threshold condition, the damage on the beam quality will be more evident.