高功率激光系统空间滤波器的重要参数

Important Parameters of Spatial Filter in a High Power Laser System

提出空间滤波器的透镜焦距需同时满足真空度和透镜球差最小的要求,滤波小孔的发散角必须小于某一定值才能有效滤除高频分量,并由此计算出本文所用高功率激光系统中的空间滤波器的小孔孔径约为20倍衍射极限。同时,分析了滤波小孔在光轴上所处位置的范围,即得出只要处于距焦平面1.04mm的范围内都是合理的结论。利用光学设计软件Fred建立模型进行验证,模拟结果表明,根据本文提出的计算方法所设计的空间滤波器能够有效地滤除系统中的高频分量和杂散光。

By means of reasonably mathematical approximation and numerical integration, the fact that the focal length of the lens in the spatial filter should simultaneously satisfy the requirement of vacuum and the minimum spherical aberration is presented. In order to filter the high frequency components, the divergence angle of the filter must be less than a certain value according to the system requirement. Therefore, the aperture of the filter hole used in the high power laser system is about 20 times of the diffraction limitation 1.04mm. In the meantime, the scope of the location of the filter hole in the optical axis is reasonable as long as the location is within the focal depth. In addition, the model was built by means of the optical design software for the validation via simulation. The key components and specifications are carefully analyzed; and new structure design and techniques are employed. The simulation results show that the designed spatial filter according to the method presented in here can effectively filter out the high frequency components and stray light in the system. In conclusion, the theoretical analysis indicates that the described method has reached the optimal design and it is feasible.