Plasma polishing processes applied on optical materials: A review

Nowadays, the surface quality of the material is crucial for industry and science. With the development of micro-electronics and optics, the demand for surface quality has become more and more rigorous, making optical surface polishing more and more critical. Plasma polishing technology is conceived as an essential tool for removing surface and subsurface damages from traditional polishing processes. The plasma processing technology is based on plasma chemical reactions and removes atomic-level materials. Plasma polishing can easily nano-finish hard-brittle materials such as ceramics, glass, crystal, fused silica, quartz, Safire, etc. The optical substrate with micro-level and nano-level surface roughness precision is in demand with the advancement in optics fabrication. The mechanical properties of super-finished optics materials are being used to fulfill the requirement of modern optics. This article discusses the processing of different types of freeform, complex and aspheric optical materials by the plasma polishing process used mainly by the optical industry. The plasma polishing devices developed in the last decade are thoroughly reviewed for their working principles, characteristics and applications. This article also examines the impact of various process parameters such as discharge power, rate of gas flow, mixed gas flow ratio and pressure on the plasma polishing process.