拼接光栅的偏差对光束空间特性的影响

用拼接小尺寸多层介质膜衍射介质膜衍射光栅的办法制作大口径的高破坏阈值光栅成为解决拍瓦激光系统输出能量的关键技术———光栅拼接技术。拼接的每个光栅都存在五维自由度的偏差,对激光脉冲的空间特性和时间特性产生影响。用夫琅禾费衍射的方法分析了拼接光栅的偏差对光束空间特性的影响,建立了偏差和远场强度分布之间的函数关系并用数值方法进行模拟,得出角度偏差对光束远场分布的影响可以忽略,而位移偏差:光栅间拼缝和前后位移偏差是影响光束远场分布的关键因素。

Effect of Tiling Gratings Errors on Laser Beam Spatial Distribution

Grating tiling technology using small aperture multilayer dielectric coating diffraction gratings to form large-aperture high-damage threshold gratings is the key technology to solve the output energy of the PW laser system.There are errors of five degrees of freedom between each adjacent pair of gratings within a tiled-grating system,affecting the spatial and temporal property of the laser beam.The authors express the relationship of far-field intensity distribution as the function of individual error by analyzing the effect of tiling gratings errors on the laser beam spatial distribution with Fraunhofer diffraction method and simulate it with numerical method.The results indicate the distortion in the pulse shape caused by angle error is negligible,the piston errors including in-plane shift and out-of-plane shift errors are the critical effects on the far-field intensity distribution.