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 withan optical one. Optical micro-resonators, storing light at certain spots, areessential for optical signal processing. Single-crystal Calcium Fluoride (CaF2) is the most suitable materialfor highly efficient optical micro-resonators, and a resonator made of CaF2can be manufactured by ultra-precision machining. However, the performance of such optical micro-resonators depends on its surface integrity.In this study,therelation 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 thatthe crystalline plane and the cutting direction constantly vary. We analyzed crack initiation and surface integrity of the entiremachined surface from the perspective of slip system and cleavage. Subsurface damage was also observed by using the TEM and X-ray analyzersfor more efficient manufacturing of optical micro-resonators.