大口径碳化硅反射镜面PVD改性工艺的研究

通过将多块不同尺寸的碳化硅平面试片以及一块口径为520mm碳化硅凹非球面反射镜作为镜面改性工艺技术的实验平台，对大口径碳化硅反射镜面PVD改性工艺技术进行探索、分析和研究。重点研究了前期PVD改性前镜面特性与PVD改性层的最佳匹配关系，主要是PVD改性层与镜面粗糙度和残留面形误差的要求和最佳结合点。采用的抛光方式为磨盘相对镜体做行星运动，采用相同的离子束辅助沉积法进行凹椭球面碳化硅反射镜的镜面改性。实验结果表明:通过选用合适的方案对改性后的PVD改性层镜面的面形误差进行修抛，可同时提高其镜面光洁度和粗糙度，最终测试结果为0.756　nm（Sq），与改性前比较，粗糙度得到一定程度的提高。

PVD Si coatings on large-aperture SiC mirror for surface-modification

Experiments on polishing and surface-modification of an aspheric surface silicon carbide (SiC) mirror with 520 mm diameter and some SiC plane mirrors with different diameters were carried out, the technology of surface-modification was analyzed and discussed in detail. The effect of surface-modification (ion beam assisted deposition) on optical properties of SiC mirrors was researched. Several types of association scheme were constituted by combining the physical and chemical behavior of physical vapor deposition (PVD) coatings with the mirror polishing technique, the PVD coatings- requirements for the surface properties before surface-modification and the optimum combining site between them were mainly studied. Results show that the polish of modified surface with suitable plan can both improve the surface error and roughness. The surface roughness of 520 mm aspheric surface SiC mirror is 0.756 nm (Sq). Compared with the surface before modified, the roughness is improved.