直接抛光后的SiC反射镜表面光学散射仍较大，无法满足高质量空间光学系统的应用需求。为此必须对SiC反射镜进行表面改性，以获得高质量的光学表面。目前国际上较为流行的是制备Si或SiC改性层进行表面改性。分别采用离子辅助电子束蒸发方法制备Si和SiC改性层进行改性，相关测试结果表明：Si改性层结构为立方相，改性后基底表面粗糙度(rms)降到0.620 nm，散射系数减小到1.52 %；SiC改性层结构为非晶相，改性后基底表面粗糙度(rms)降到0.743 nm，散射系数减小到2.79 %。两种改性层均与基底结合牢固，温度稳定性较高。从可靠性方面考虑，目前在国内第一种方法更适于实际工程应用。该工艺改性后SiC基底表面散射损耗大大降低，表面质量得到明显改善，镀Ag后表面反射率接近于抛光良好的微晶玻璃的水平，已能够满足高质量空间光学系统的应用需要。

The SiC material can't meet the application requirement of high quality space-used optical system because the considerable surface scattering on the SiC mirror after polish. So the surface modification must be taken on in order to obtain high quality optical surface on the SiC mirror before use. The two prevailing international methods for surface modification are to use of Si coating and SiC coating. Surface modifications are made by the two means using e-beam evaporation with ion assisted. Test results show that the Si coating is cubic phase. Surface roughness(rms) of the SiC substrate is reduced to 0.620 nm and scattering coefficient is reduced to 1.52% after Si coating modification. The SiC coating is amorphous. Surface roughness(rms) of the SiC substrate is reduced to 0.743 nm and scattering coefficient is reduced to 2.79% after SiC coating modification. The modification coatings both have a good temperature stability and a high adhesion to the SiC substrate. Evaluated by the reliability the method of using Si coating is much more compatible for the engineering application interiorly. After the surface modification by means of using Si coating, the wastage of surface scattering is reduced greatly and the quality of optical surface is improved obviously. The surface reflectance with Ag coating is obviously enhanced to that of fine polished zerodur glass, thus it can meet the application requirement of high quality space-used optical system.