Full-band surface processing method of meter-scale large-aperture polarizer

Abstract

A method for processing the full-band surface shape of a meter-scale large-diameter polarizer. The method of the present invention combines magnetorheological polishing with conformal smooth polishing, which can effectively control the processing accuracy of the meter-scale large-diameter polarizer, and manufacture a high-power In the laser system, the meter-level large-aperture polarizer element with full-band indicators meeting the standard, the specific indicators on both sides of the transmission and reflection are as follows: PV≤λ / 3, GRMS≤7nm / cm, PSD1RMS≤1.8nm, PSD2RMS≤1.1nm, surface roughness≤1nm .

Description

technical field [0001] The invention belongs to the processing of optical elements, in particular to a method for processing the surface shape of a meter-level large-diameter polarizer in full frequency range. technical background [0002] In a high-power laser system, in order to obtain the ideal beam focusing quality, the surface error of precision optical components must not only achieve good low-frequency surface accuracy, surface quality and ultra-smooth surface roughness indicators, but also meet extremely strict intermediate frequency requirements. The wavefront error requirement, that is, the wavefront error requirement is for the entire frequency band. According to the influence of different frequency band errors on optical performance, the surface error of optical components in NIF is divided into three spatial frequency bands: [0003] Low frequency band (error space period length L>33mm), [0004] Middle frequency band (33mm≥L≥0.12mm), [0005] High-frequen...

AI Technical Summary

Problems solved by technology

On the other hand, for the annular polishing process of large-diameter optical components, even if the rotational speed of the polishing disc is small, due to the large size of the workpiece itself and the weight of the correction disc, the heat generated by friction is easy to accumulate, and the control of the surface shape brings very serious negative impact

In addition, the more important thing is that the uniformity of the UBK7 material used in the polarizer element that can be obtained in China is the best to reach 3ppm, and the thickness of the polarizer element is greater than 90mm, and the transmission wavefront error caused by the uniformity is greater than λ / 3 (λ=632.8nm) requirements, it is theoretically impossible to achieve the processing requirements of the transmitted wavefront by using the annular polishing technology

[0009] The small tool polishing technology with computer control as the core, such as small grinding head polishing technology, magnetorheological polishing technology and ion beam polishing technology, etc., can well overcome the problem of material refractive index non-uniformity due to the ability of local surface shape correction , to achieve high-precision low-frequency reflection and transmission surface processing, but because the CNC small tool polishing technology uses a grinding head that is much smaller than the workpiece size, small-scale intermediate frequency waviness problems will occur on the surface of the workpiece, resulting in the It is difficult to meet the requirements of the frequency band error of the processed surface

Therefore, it is impossible to meet the full-band index of meter-scale large-diameter polarizers by using ring polishing or CNC small tools alone.