To eliminate surface limitation caused by Silicon impurity in RB-SiC apace mirrors

a relatively thick Si film is deposited on well finished RB-SiC substrate by ion assisted depositing(IAD) process to provide a better polishable surface. Firstly，The process of RB-SiC surface coating is summarized

on the polishing point of view. Secondly

severial properties of IAD-SiC coatings were tested. Results show that the amorphous film can satisfy all requirements of RB-SiC surface coating technique. Then

polishing experiments on 10±0.5m thick IAD-SiC layers were accomplished and testing results of surface roughness and reflectivity were given: surface roughess of the coating after polished achieved less than 0.5nm RMS ; moreover

reflectivity of IAD-Si polished surface with reflective films increased up to 4.5% than that of RB-SiC in 360-1100nm wavelength. The results indicated that IAD-Si coating technique and the new polishing process showed an access to high quality RB-SiC space mirrors.