大口径衍射光学束匀滑器件的研制

Development of large aperture diffractive optical elementfor beam smoothing

采用爬山 -模拟退火混合优化算法 ,选取合适的权重因子 ,改善了衍射光学束匀滑器件的设计性能 ,其顶部不均匀性小于 1 % ,能量利用率优于 95%。采用旋转镂空掩模板 ,加工出 1 80的束匀滑器件 ,并进行了实验研究 ,获得了较好的束匀滑光强包络。为获得真实的束匀滑分布、改善顶部均匀性、提高抗波前畸变宽容度 ,选取特定的焦面采样间隔进行了精细化设计。

In this paper, the hybrid optim iz ation algorithm, combing Hill climbing and Simulated Annealing, is adopted to d esign the diffractive optical element (DOE) to realize beam smoothing. The perfo rmance of the DOE is improved by choosing suitable weight factor in the optimiza tion, the non uniformity is optimized to be less than 1% and the light efficien cy greater than 95%. A large aperture DOE with diameter 180mm is fabricated by i on etching with a hollowed out mask. The intensity distribution of the focused spot is measured and a rather good intensity envelope has been obtained, withou t the center zeroth order pulse but with a rather large high frequency top mod ulation. Furthermore, to realize a true beam smoothing, improve the top uniformi ty and increase the tolerance of phase distortion, the precise design of a one d imensional DOE is completed by using a specially chosen sampling interval in the optimization.