Silicon (Si) single crystal is a chemically inert material with high hardness and insolubility in water It has good light transmission performance in the 1.2-7 μ m wavelength range, and also has good light transmission performance in the far-infrared wavelength range of 300-300 μ m, which is a characteristic that other optical infrared materials do not have. Silicon (Si) single crystals are commonly used as substrates for 3-5 μ m mid wave infrared optical windows and optical filters Due to its good thermal conductivity and low density, this material is also a commonly used material for making laser reflectors, infrared thermometers, and infrared optical lenses.