Investigation and modeling of orientation-determined removal characteristics of KDP crystal in microemulsion abrasive-free jet polishing from nano to macro scale

Microemulsion abrasive-free jet polishing (MAFJP) technology is a novel non-abrasive removal technique that exhibits unique advantages in polishing nonlinear KDP optical material. During MAFJP, the nanoscale water cores in MAFJP fluid impact and slip on the KDP surface, thus leading to contact with the KDP atoms and achieving defect-free removal of KDP through water dissolution. Dissolution is the inverse process of crystal growth and exhibits significant anisotropy. This work first investigated the orientation-determined KDP dissolution removal characteristics. At first, we gained insights into the impacting process of nanoscale water cores based on molecular dynamics simulation and then established an MAFJP removal function model to describe the removal process for KDP. The model considers the dynamic impacting and slipping dissolutions of (001), (010), (100), (111), I-type, and II-type crystal planes, and the final calculated results match perfectly with actual experimental results. This research elucidates the mechanism of orientation-determined MAFJP on KDP, and will promote the application of MAFJP technology in the polishing of single-crystal anisotropic optical materials.