The focal length of the lens in the spatial filter should simultaneously satisfy the requirement of vacuum and the minimum spherical aberration. 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. So the aperture of the filter hole used in the high power laser system is about 20 times of the diffraction limitation. At the same time, the scope of the location of the filter hole in the optical axis is reasonable as long as the location within the focal depth. In addition, the model was built by means of the optical design software to simulate validation. The simulation results show that the designed spatial filter according to the method presented in the paper can effectively filter out the high frequency components and stray light in the system.
A technique for high-frequency scanning of high power laser light for laser-wire scanners at electron accelerators
