Polishing process of single crystal sapphire substrate based on femtosecond laser

Monocrystal sapphire have excellent properties such as high strength, hard and brittle, high temperature resistance, chemical corrosion resistance, wear resistance and good infrared transmittance, which are widely used in semiconductor, defense, aerospace and other frontier fields. As a typical hard and brittle material, sapphire has become an obstacle to the development of its application for ultra-precision machining with high efficiency and low damage. Therefore, a suitable method is needed to achieve ultra-precision processing of monocrystal sapphire. Different from traditional machining, laser polishing technology has the characteristics of non-contact processing and no mechanical processing stress, while femtosecond laser processing technology has the advantages of cold processing and no selectivity to the material, so it is suitable for surface polishing of sapphire. In this article, the influence of the femtosecond laser with the center wavelength of 515 nm on the surface polishing of sapphire under different processing modes, scanning interval and scanning speed was studied. By adjusting the laser parameters, the surface roughness of single crystal sapphire was reduced from 1.58 μm to less than 0.3 μm by femtosecond laser polishing.