结合非线性强度和相位调制作用,研究束匀滑相位板整形焦光斑在焦面附近传输变换的特性。采用衍射光学理论方法来计算三维空间离焦面上的光场分布,引入光斑落点漂移和光强对称度两个指标参量来表征光斑在传输演化过程中的性能。研究分析了高通量激光辐照下非线性效应对连续相位板整形焦斑的影响,尤其是楔形透镜厚端和薄端的较大差异引起的小尺度自聚焦强度调制差异,该差异使得光斑传输至焦点后的一段距离后开始渐渐偏离光轴,同时其整体强度分布也出现不对称度偏置。结果表明,非线性强度畸变的影响远大于相位畸变的影响,在给定激光装置光路中5 GW/cm ²功率密度的入射条件下,焦点后4 mm处光斑落点漂移超过0.1 mm,光强左右不对称度偏置达到30%。

Transmission characteristics of smoothed beam spots near the focal plane were investigated under the influence of nonlinear intensity and phase modulation. Diffraction theory was used to calculate the light field distribution on the defocused surface in three-dimensional space. Spot position drift and intensity symmetry were used to characterize beam spot performance during transmission evolution. The impact of non-linear effects under high-flux laser irradiation on smoothed spot of continuous phase plate was studied. Especially, the small-scale self-focusing intensity modulation difference caused by large difference between the thick and thin ends of wedge lens resulted in gradual deviation of beam spot from the optical axis during the defocusing transmission process, and caused asymmetric bias of intensity distribution. The results show that the effect of nonlinear intensity distortion is far greater than that of phase distortion. Under irradiation with 5 GW/cm 2 power density on a given laser device, the spot position offset is more than 0.1 mm on the 4 mm defocused plane, and the asymmetry of light intensity is biased to 30%.