A study on mechanical processing characteristics of Si grating

We conducted research on ruled type grating, which is a method of manufacturing grating spectroscopic devices through mechanical processing. Grating is an optical component that specifies light through a multi-layer grid pattern structure and analyzes the characteristics of the measurement target using a spectrum according to the wavelength. The sharper the end of the blaze angle of the grating pattern designed for spectroscopy, the higher the reflectance and thus the higher optical efficiency. We adopted a cutting method through mechanical processing to sharpen the end of the blaze angle. In addition, the higher the refractive index, the smaller and lighter the spectroscopic equipment can be, so single crystal silicon material with a refractive index of n=3.5 (wavelength 1,000 nm) was used. However, Single crystal silicon material has low mechanical process ability due to its brittle nature with high hardness and low fracture toughness. To ensure process ability, we used ultra-precision grooving equipment to check the surface roughness tendency of the pattern surface according to the processing conditions of tool shape, tool feed speed, and cutting depth. Surface roughness was measured at several points on the pattern using a white light interferometer. As a result, we conducted basic research to derive the optimal processing conditions for Si gratings through the analysis of surface roughness trends and surface quality according to the processing conditions.