采用二维加权串行迭代算法(WSI)设计了8台阶的衍射光学元件(DOE)进行激光光束整形,将圆形高斯激光束变换为10 μm×10 μm的方形均匀焦斑,同时满足了二维激光光束形状的改变及振幅分布均匀化的功能;应用到高密度全息存储中,实现了入射到记录材料上焦斑强度的均匀分布。模拟计算结果表明,转换到均匀区的能量效率达到91.2%,平顶区的不均匀度为4.6%,误差小于0.023%,基本上达到了设计的要求。同时分析了衍射光学元件对入射高斯光束的束腰半径及傅里叶变换透镜焦距的宽容度,还制作出了8台阶量化相位衍射光学元件的三套掩膜板。

A diffractive optical element (DOE) with 8 levels is designed to implement the wavefront transformation with two-dimensional weighed serial iterative algorithm. The DOE converts a circular-Gaussian laser beam into a 10 μm×10 μm flat-top square focused spot, which realizes the transformation of beam-shape and the uniform distribution of the amplitude at the same time. The DOE is applied to high-density holographic storage, and it meets the needs of the uniform distribution of the incident focused spot. The simulated results show that the energy transformation efficiency is up to 91.2%, the uniformity error is 4.6%, and the error is below 0.023%, which nearly satisfy the need. The tolerance of the incident beam and the focus is analyzed too. Three sets of masks on 8 levels phase DOEs have been processed.