Nanometer-scale polishing of diamond by pulsed laser using feedback from interferometric topography measurement

Owing to its exceptional properties, diamond has potential applications ranging from ultra-precision tools to semiconductors. However, the extreme hardness of diamond makes machining challenging, and conventional methods, such as chemical–mechanical polishing, encounter limitations. A polishing technique that achieves nanometer-level accuracy with minimal material removal while maintaining high machining flexibility has yet to be established. In this study, we propose a feedback polishing method that integrates an on-machine white-light interferometer (WLI) with an ultrashort pulse laser (USPL) within a common optical system. By setting machining conditions according to WLI-measured surface topography, the method selectively remove protrusions at the nanometer scale. Machining characteristics were compared at 1030 nm and its second harmonic (515 nm). Under the 515 nm condition, the surface roughness was reduced from approximately 80 nm to a minimum of 33.6 nm. Although no significant difference was observed in the minimum achievable roughness between the two wavelengths, the removal depth per pulse depended on the wavelength and pulse energy. These results highlight the potential of dynamically optimizing machining parameters according to the progress of feedback machining.