激光辐照靶面产生的后向受激布里渊散射(SBS)光经连续相位板(CPP)调制会产生衍射强值并对光学元件造成损伤。利用建立的SBS激光后向近场衍射传输模型及菲涅耳衍射理论,分析并数值模拟了衍射距离、CPP设计参数和应用位置等参量对近场衍射调制的影响。结果表明:在一定范围内,近场调制度随衍射距离的增大而迅速增强;CPP相位幅度、最小空间周期和频谱控制均会影响近场调制,其中相位幅度的影响较大;倍频CPP对近场调制的影响小于基频CPP对近场调制的影响。CPP后向近场衍射传输分析有助于理解相位型光学器件的近场光强分布,对高功率激光系统中光学元件的排布及CPP的优化具有指导意义。

The stimulated Brillouin scattered (SBS) light caused by laser irradiation at target is modulated when passing through a continuous phase plate (CPP), which causes damage to optical elements. In this paper, a theoretical model for analyzing back near-field diffraction transmission of SBS light is established, which is combined with Fresnel diffraction theory and used to analyze and numerically simulate the influences of diffraction distance, CPP parameters and application position on near-field diffraction modulation. The results show that as the diffraction distance increases within a certain range, the near-field modulation increases rapidly. Near-field modulation is affected by CPP phase amplitude, minimum spatial period and spectral control, in which phase amplitude has a relatively high impact. In addition, the effect of doubling frequency CPP on near-field modulation is weaker than that of fundamental frequency CPP. The study of back near-field diffraction transmission of CPP is helpful for understanding the near-field intensity distribution of a phase optical device and provides some guidance on the arrangement of optical elements of a high-power laser system and the optimization of CPP.