基于单压电变形镜的可控环形焦斑整形

Generation of tunable annular focal spot using unimorph deformable mirrors

为了实现可控环形焦斑的整形,提出了一套基于单压电变形镜的整形方法。首先结合波前衍射理论和随机并行梯度下降算法模拟迭代出环形焦斑整形所需的调制相位,进而利用波前传感器探测光束的波前信息,控制变形镜重构目标光斑对应的调制相位,实现聚焦光斑的整形。搭建了一套基于62单元单压电变形镜的光斑整形实验平台,采用焦平面上的CCD记录远场聚焦光斑。实验结果表明,该方法实现了对不同直径(0.32,0.4,0.6 mm)和宽度(0.05,0.08,0.1mm)环形焦斑的整形,可有效应用于激光束整形。

In order to generate a tunable annular focal spot, a laser beam shaping method using a unimorph deformable mirror was proposed. The wavefront phase used for generating a target annular focal spot was simulated iteratively by combining diffraction theory and the stochastic Parallel Gradient Descent Algorithm （SPGD）. The wavefront phase was then reproduced using a deformable mirror with the feedback of the measured wavefront obtained from a wavefront sensor to realize the shaping of the focal spot. A beam shaping system based on a unimorph deformable mirror with 62 actuators was established. The far-field focal spot was measured using a Charge Coupled Device （CCD） placed at the focal plane of the system. Annular focal spots with different diameters （0.32 mm, 0.4 mm, and 0.6 mm） and widths （0.05 mm, 0.08 mm, and 0.1 mm） were generated experimentally based on the proposed method. This demonstrates that the proposed method is suitable for laser beam shaping.