Silicon (Si) single crystal is a chemically inert material with high hardness and insoluble in water. It exhibits high transparency in a broad wavelength range from 1μm to 7μm. At the same time, it also shows a good transmittance in the far-infrared band of 100-300 μm. This is a unique advantage of silicon single crystal materials compared to other infrared materials. Silicon (Si) single crystals are commonly used in 3-5 μm mid-infrared optical windows and optical filters. Due to its good thermal conductivity and low density, silicon single crystal is also a common material for laser mirrors.