Study on the technological method of ultra-precision grinding for parabolic mirror of monocrystalline silicon

Curved optics of monocrystalline silicon plays an important role in high power laser system and its form accuracy and subsurface damage (SSD) have a significant impact on the performance of the laser system. In order to improve grinding accuracy and control the depth of SSD, the ultra-precision grinding (UPG) process of Si is studied. Firstly, the grinding theory is introduced and the relationships among the depth of cutting, the depth of subsurface cracks and the load of single particle are analysed. Then the influence of different process parameters on the surface quality of Si was investigated by some process experiments. Based on the result of process experiments, the processing of a 195 mm-diameter parabolic mirror of Si was carried out. The results show that the form accuracy of peak-valley value is promoted up to 3.77 μm from 21.4 μm and Rms value of the roughness is improved up to 0.11 μm from 0.625 μm.