以提高共焦差动并行激光直写中光束刻写质量为目标, 分析设计了调平聚焦伺服控制系统。采用柱面镜作为像散元件, 与四象限光电探测器结合, 利用差动像散检测方法和比例积分微分(PID)反馈算法减少光源和外部干扰的误差, 获得高灵敏度、高精度、高稳定性的探测曲线。通过优化光学设计参数, 本系统能获得具有高灵敏性与一致稳定性的探测曲线, 探测范围为3 μm, 静态聚焦误差可达 ±5.0 nm; 动态聚焦压电陶瓷(PZT)伸长量可保证在焦深范围内, 焦点位置辨别精度可达纳米量级, 可探测调平台的倾斜角和俯仰角在0.01 mrad左右。利用该系统可实现光栅的刻写, 进一步为更大尺寸、更高密度的光栅刻写提供依据。

A leveling and focusing servo control system is built to improve the focus accuracy of the differential parallel confocal laser direct writing system. To obtain a detection curve with high sensitivity, accuracy and stability, the cylindrical lens as an astigmatism element is combined with four-quadrant photodetector, and the differential astigmatism detection method and proportion integration differentiation(PID) feedback algorithms are employed to reduce errors caused by light source and external interference. By optimizing the optical parameters, the detection curve with high sensitivity and stability has been obtained, with a range of around 3 μm and a static focusing error of ±5.0 nm. The stretching of piezoelectric ceramic transducer(PZT) can be guaranteed within the depth of focus range in the dynamic mode. Nano-scale precision of the focal position can be achieved, and the tilt and pitch of lever adjuster approximate 0.01 mrad. Utilizing this system, gratings can be fabricated, and this system can provide reference for the fabrication of larger-size and higher-density gratings in the future.