数值模拟了拍瓦激光器前端非共线光参变放大(OPA)过程中存在波前畸变的抽运光对信号光光束质量的影响。结果表明,当抽运光光束波前存在严重畸变时,衍射效应和走离效应通过不同的物理机制导致了信号光光束质量的急剧下降。在导致信号光光束质量下降的过程中,走离效应在OPA未饱和放大时起着主导作用,当OPA工作在过饱和状态时,过饱和导致的信号光近场空间分布中心凹陷成为光束质量下降的主要因素。

The influence of wave-front-distorted pump pulse on the beam quality of the amplified signal pulse in the non-collinear optical parametric amplification (OPA) is numerically simulated.The results indicate that diffraction and walk-off effects degrade the signal beam quality via different physical process when the wave-front of pump laser pulse is distorted seriously.Walk-off effect is the main factor to degrade the beam quality of the signal pulse when OPA works in linear regime.The sunken-center of spatial beam shapes induced by oversaturation of OPA play the dominant role in the degradation of beam quality when OPA works in oversaturated regime.