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Home > Blog >

China Successfully Developed The World's Largest Diameter Monolithic Silicon Carbide Mirror

2019-06-19
The National Major Scientific Research Equipment Development Project undertaken by the Changchun Institute of Optics, Fine Mechanics and Physics of the Chinese Academy of Sciences has passed the project acceptance test for the “4 m high-precision SiC aspheric mirror integrated manufacturing system”. This is the world's largest calibre silicon carbide single mirror, which marks the world's advanced optical system manufacturing capability and has laid a solid foundation for the leap-forward upgrade of China's large-caliber optoelectronic equipment.
 
4 meter diameter high precision silicon carbide aspheric mirror
Large-diameter high-precision aspheric optical mirrors are the core components of high-resolution space-to-surface observation, deep-space exploration and astronomical observing systems. The level of manufacturing technology is of great significance to a country's national defense security, national economic construction, and basic scientific research capabilities. It is also an important indicator to measure the level of development of a national high-performance optical system. Silicon carbide ceramic materials are recognized as high-stability optical mirror materials in the international optical world. The use of silicon carbide materials can greatly improve the performance of large-caliber imaging systems. For example, for an optical telescope, the aperture of the mirror determines the resolution of the telescope—the more the telescope with a large aperture mirror, the clearer it is.
 
However, it is very difficult to make a "big mirror" that can be used scientifically. When the caliber exceeds a certain level, it will bring great challenges to optical materials and optical processing. 4 meters, is a ridge - taking visible light band observation as an example, the surface accuracy is also better than the mirror level of 20 nanometers. Compared with the 4 meter mirror, this is roughly equivalent to the size of Beijing. Land leveling to height difference is less than 1 mm. For a long time, large-caliber mirror mirror blank manufacturing and mirror processing technology has been mastered by a few Western countries such as the United States, France, and Germany. China has never had the ability to independently manufacture large-diameter mirrors of the order of 4 meters.

Under the leadership of the project leader and researcher Zhang Xuejun of the Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, the project research and development team completed nine years of technical research and completed the preparation of silicon carbide mirror blanks, aspherical surface inspection, and silicon carbide surface modification coating. The research and development of manufacturing equipment and manufacturing process have formed a 4 m high-precision silicon carbide aspheric integrated manufacturing platform with independent intellectual property rights, and completed the development of high-precision silicon carbide aspheric products of 4 meters.
Zhang Xuejun introduced that the main key technical bottlenecks in the manufacture of large-diameter high-precision silicon carbide aspheric mirrors are three aspects: silicon carbide material preparation, aspheric surface processing inspection and high-performance modified coating. In the preparation technology of silicon carbide materials, the R&D team mastered a number of key technologies for mirror blank preparation, established a large-diameter silicon carbide mirror blank manufacturing platform, and successively developed a 2 m, 3 m single silicon carbide mirror blank, 4 m caliber The overall silicon carbide mirror blank realizes the independent controllable of China's large-diameter silicon carbide optical materials. In the aspect of large-diameter silicon carbide aspheric processing technology, the R&D team developed the aspherical NC machining center that was successfully applied for the first time in China, creatively proposed an integrated processing equipment solution, and completed the high-precision machining of a 4 m-scale silicon carbide aspheric surface. The processing precision is better than 16 nanometers, and the high-precision processing and detection technology of silicon carbide in 4 meters is fully controllable. In the large-diameter silicon carbide modified coating technology, the R&D team has successfully developed the SiC mirror modification and reflective film plating integrated equipment for the first time in the world. For the first time, the magnetron sputtering technology was used to complete the surface modification of 4 m silicon carbide. To meet the polishing requirements of high-quality optical surfaces, the high-reflectivity film coating on the surface of 4m silicon carbide mirror can be seen, and the full-wavelength reflectance of long-wave infrared is better than 95%.

According to reports, the 1.5-meter and 2-meter-scale silicon carbide aspheric mirrors developed based on this project have been successfully applied to national major model tasks. In the future, the 4 m-scale silicon carbide aspherical mirror will also be applied to the national large-scale photovoltaic system, solving the core technical problems for the development of large-caliber optical systems.