为了提高强激光系统中输出光束的光束质量, 提出了一种利用三光斑来探测离焦的方法, 该方法能够在探测器上横向探测光束轴向上三处位置的光斑尺寸, 通过三光斑间的尺寸关系可计算出光束的离焦量, 进而根据离焦量进行闭环校正。实验中通过调节整形系统对光束的离焦量进行离焦补偿, 使得光束离焦量从(4.9±0.2) mm校正至(0.3±0.1) mm。实验结果表明, 该方法结构简单, 能够测量各种因素引起的强激光的发散会聚度, 给出了离焦补偿的可靠判据, 为解决强激光热效应造成的光束发散提供了一种新方法。

In order to improve the beam quality of output beam in high power laser system, a method to detect defocus by using three spot sizes was presented, the spot sizes at three positions in the axial direction of the beam on the CCD detector was detected using the method, the defocusing amount of the beam can be calculated by the size relationship among the spots, and then closed-loop correction was performed according to the defocusing amount. In the experiment, the defocusing amount of the beam was compensated by adjusting the shaping system, so that the defocusing amount of the beam was corrected from (4.9±0.2) mm to (0.3±0.1) mm. The experimental results show that the method is simple in structure, and can measure strong laser convergence and divergence caused by various factors. The study provides reliable criteria for defocusing compensation, and a method to solve the problem of beam divergence caused by strong laser thermal effect.