The technical research on fabricating large aperture flat SiC mirror

A 520mm aperture SiC flat mirror was manufactured up to RMS accuracy of 10.8nm in 50 days. Through the analysis of SiC material removal principle during full aperture polishing, we chose the appropriate parameters of polishing in full aperture polishing process and quickly made the surface error convergence to RMS value 100nm, then we took the step to small tool polishing, the adjustment of the remove function in this process was taken in order to coordinate the hard material's properties, the efficiency in PV and RMS convergence was presented according to the experimental results. After four week's polishing, the RMS value successfully reduced to 10.8 nm and reached the technical requirements of this large flat SiC mirror.