激光波前功率谱密度与焦斑旁瓣的关系

基于波前功率谱密度(PSD)的定义,分析了采用功率谱密度方法研究中频波前畸变与焦斑旁瓣关系的可行性。由于任意形状的波前畸变都可以由不同空间频率的正弦函数叠加组成,以正弦函数波前为例进行功率谱密度分析和远场分析。分析表明,当中频波前畸变的幅度满足一定条件时,远场二级以上的衍射非常低,可以忽略不计,此时波前功率谱密度与焦斑旁瓣具有非常好的相似性,并且这种相似性仅与中频波前畸变的幅度有关,与空间频率无关。最后还用数值模拟的方法验证了这个结论对叠加后的结果仍然成立。研究结果可以用于设计满足惯性约束聚变(ICF)驱动器打靶对焦斑旁瓣要求的光学元件中频段波前畸变指标。

Relation between Wavefront Power Spectral Density and Wings of Focal Spot

From the definition of wavefront power spectral density(PSD),the feasibility of studing the relationship between the middle-frequency wavefront distortion and wings of the focal spot is analyzed.The arbitrary shape wavefront distortion being composed of sine function of different spatial frequencies,it is natural to make analysis of PSD and the far field by using sine function as a example.The result shows that the diffraction in the far field whose order is larger than 2 is negligible when some conditions about the amplitude of the middle-frequency wavefront distortion are satisfied.In this case,wonderful similitude exists between PSD and wings of focal spot,and the factor affecting the similitude is the amplitude of the middle-frequency wavefront distortion not the spatial frequency.In addition,numerical simulation is carried out to demonstrate the accuracy of the conclusion when it is applied to the overlapped case.The conclusion of the paper is benefit to specify the middle-frequency wavefront distortion of optics for meeting the aim of inertial confinement fusion(ICF) driver.