Experimental analysis of the surface integrity of single-crystal calcium fluoride caused by ultra-precision turning

To achieve maximally efficient signal processing, an electrical signal processing circuit needs to be replaced with an optical one. Optical micro-resonators, storing light at certain spots, are essential for optical signal processing. Single-crystal Calcium Fluoride (CaF₂) is the most suitable material for highly efficient optical micro-resonators, and a resonator made of CaF₂ can be manufactured by ultra-precision machining. However, the performance of such optical micro-resonators depends on its surface integrity. In this study, the relation between the crystal anisotropy and surface integrity after ultra-precision cutting was investigated. The most difficult point in the cylindrical turning of a crystalline material is that the crystalline plane and the cutting direction constantly vary. We analyzed crack initiation and surface integrity of the entire machined surface from the perspective of slip system and cleavage. Subsurface damage was also observed by using the TEM and X-ray analyzers for more efficient manufacturing of optical micro-resonators.