High-efficiency machining of silicon carbide Fresnel micro-structure based on improved laser scanning contour ablation method with continuously variable feedrate

In order to achieve high-efficiency machining of Fresnel microstructure, an improved laser scanning contour ablation (LSCA) method with continuously variable feedrate was proposed based on the theoretical model of the material removal depth. The silicon carbide (SiC) Fresnel microstructure was machined by the improved LSCA method and characterized by multiple means. The experimental results showed that the crystallinity of SiC decreased and amorphous Si and SiO₂ were generated on the SiC Fresnel microstructure. The form profile error PV was less than 5 μm, the average verticality error of the step sidewall was 34.6°, the surface roughness was Sa 0.237 μm–0.343 μm, the subsurface cracks depth was 1–1.5 μm. The material removal rate (MRR) of machining SiC Fresnel microstructure by using the improved LSCA method could achieve 0.2875 mm³/min, which was much higher than the MRR of mechanical machining and reflected the efficiency advantage of laser to process hard and brittle materials.