Reverse growth surface planarization mechanism and high-efficiency polishing of KDP

This paper proposes a reverse growth surface planarization mechanism for achieving high-efficiency precision processing of the potassium dihydrogen phosphate (KDP) crystal. The KDP crystal reverse growth has ordered and controllable characteristics similar to growth, which differs from the disordered and random dissolution in the natural state. Experiments are conducted using a high-precision annular polisher to investigate the surface characteristics, material removal, and surface planarization of different crystallographic planes in reverse growth. The repeat utilization of polishing liquids is studied to reduce processing costs. The difference in material removal and surface roughness of different crystallographic planes obtained from the same reverse growth polishing process is within 8%. The suitable undersaturation range for reverse growth surface planarization is 0.01–0.18, with a maximum material removal rate of 90 μm/min, 50 times that of the microemulsion polishing methods. Finally, a mirror-like KDP crystal surface is obtained with a surface roughness Ra of 0.00975 μm.