Water dissolution polishing for potassium dihydrogen phosphate crystal without abrasive using sol-gel tool

Potassium dihydrogen phosphate (KDP) crystal is an excellent nonlinear optical material, which is widely used in nonlinear optics. The KDP crystal possessing the properties of moisture absorption and deliquescence belongs to soft and brittle material, regarded as extremely difficult to machine by the conventional methods. In this paper, a novel KDP crystal polishing technology has been proposed, which used sol-gel (SG) tool for water dissolution finishing of KDP crystal without abrasives. The surface morphology is detected by 3D video microscope, and the surface roughness is detected by 3D optical profiler. Results indicate that the new method can obtain smooth surfaces efficiently and quickly. After polishing for 10 minutes, the original surface roughness is reduced from Ra 695.7 nm to Ra 17.8 nm, and the surface is smooth without scratches. This KDP crystal polishing method has broad prospects.