Ultra-Precision Machining and Surface Evaluation of Optical Flats for High Power Ultra-Violet Lasers

本研究的最终目的是开发高精度、高透明度或高反射率、高激光损伤阈值、高响应波长的高功率紫外激光平板光学元件，为高功率准分子激光器和激光聚变计划的发展提供帮助。1)利用超精密平面磨床和SDI500-75-B金刚石砂轮对各种玻璃表面进行研磨，获得了Rmax<5 nm或RMS<0.5 nm的表面粗糙度。采用浮法抛光技术对高功率紫外光激光器的反射镜材料CVD-SiC进行了抛光。因为化学气相沉积薄膜不是…的，所以在浮动抛光后可以看到晶界的台阶在晶体取向上沉积更均匀。在较小尺寸的颗粒中获得了0.2 nm RMS的表面粗糙度。在碳化硅上沉积均匀的CVD-碳化硅薄膜的发展，将使光滑的光学表面成为浮法抛光后的镜面。2)让·M·贝内特博士来到中部大学，为她的针式超精密表面粗糙度测量系统进行维修，这是世界上最灵敏的针式系统，其噪声水平为0.05 nm RMS。具有诺玛斯基干涉显微镜的新型扫描隧道显微镜是与精工电子工业合作开发的。用JOEL研制了磁控溅射装置，用于测量15OX15OX30 mm大尺寸样品的STM图像。3)用高功率激光照射研磨和光学抛光的LHG-8激光玻璃样品，测量激光损伤阈值。在地面上测得损伤阈值为25J/cm。该值远高于光学抛光表面上的值。较少

The final objects of this study is to develop the flat optical components having high accuracy, high transparency or reflectivity, higher laser damage threshold and higher responsibility for high power lasers of ultra-violet in wavelength, in order to help the development of high power excimer lasers and laser fusion program. This year's study was performed in the following three parts; ultra-precision machining of optical materials, establishing the surface roughness measuring systems in high precision and measuring laser damage thresholds in machined surfaces.1) The surface roughness of less than 5nm Rmax or 0.5nm rms was obtained on various glass surfaces ground by using the ultra-precision surface grinder and a SDI500-75-B diamond wheel. The CVD-SIC on SiC which seems to be one of the ideal material as mirrors for high power ultra-violet lasers have been polished by the float polishing. The steps at grain boundaries have been seen after float polishing because the CVD film was not … More deposited uniformly in crystallographic orientation. The surface roughness of 0.2nm rms was obtained in a grain of small size. The development of uniform CVD-SIC film on SiC will introduce the smooth optical surface as a mirror after float polishing. The fused silica as the material of transparency in ultra-violet wavelength was polished into 0.14nm rms by the float polishing.2) Dr. Jean M. Bennett came and stayed in Chubu University to fix her stylus- type ultra-precision surface roughness measuring system which is the most sensitive stylus system in the world and its noise level is 0.05nm rms. New scanning tunneling microscope having a Nomarski interference microscope has been developed with Seiko electronic industry. Magnetron spattering apparatus was also developed with JOEL for measuring STM image on bigger-sized sample of 15OX15OX30 mm.3) High power laser was irradiated on ground and optically polished LHG-8 laser glass samples for measuring laser damage thresholds. The damage threshold of 25J/cm was obtained on ground surface. This value is much higher than that on optically-polished surfaces. Less