Submicrometer-scale 3D grinding of diamond by ultrashort pulse laser with in-process interferometric topography measurement

Diamond is a promising material for advanced industrial applications such as optical components, semiconductor devices, and cutting tools due to its outstanding mechanical, thermal, and optical properties. However, these same properties make it extremely challenging to achieve both high shape accuracy and superior surface quality simultaneously. Although chemical mechanical polishing has been widely adopted and matured in practice, significant challenges remain, including limited capability for three-dimensional shaping, the risk of pressure-induced cracking, and low material yield. Ultrashort-pulse laser (USPL) processing has attracted increasing attention as an alternative, non-contact and high-speed approach capable of handling complex geometries, and parallel irradiation in particular enables a favorable balance between shape accuracy and low surface roughness. Nevertheless, conventional USPL processing has struggled to achieve nanometer-scale surface roughness and sub-micrometer shape accuracy on arbitrary three-dimensional surfaces. In this study, we propose a feedback USPL grinding method that integrates nanometer-precision, on-machine interferometric topography measurement into the laser processing workflow. By dynamically updating the processing strategy based on real-time surface profile data, the proposed method enables highly reproducible and precise shape control. Submicrometer-scale grinding of a 100-μm-scale microlens structure is demonstrated, achieving mean absolute shape error of approximately 130 nm. The proposed approach is applicable to a wide range of materials and geometries and is expected to significantly reduce subsequent polishing time when introduced as a pre-processing step. Future work will focus on extending the method to more complex geometries and further improving control accuracy.