リン酸二水素カリウム単結晶の飽和水溶液中におけるレーザビーム走査による研磨

Abstract

Potassium dihydrogen phosphate (KDP) is a non-linear optical and water-soluble crystal. However, since KDP is brittle material, it takes a large cost to obtain the surface roughness required in generating harmonics. Therefore, a new polishing method using YAG laser beam is developed and verified the method by experiments in our research work. The method developed in this paper is as follows. A YAG laser beam is focused at an edge of an end face of a single crystal in a saturated solution. The laser beam is scanned along the edge of the end surface. It is possible to polish the scanned surface by the solution of the crystal and the other portions are not removed in a saturated solution. In this paper, the surface of the crystal polished by our laser beam scanning method was compared with that polished by sandpapers. The surface polished by laser beam scanning is smoother than that polished by sandpapers when the both surface roughness were same. The crystallinity of both crystals after polishing were same degree by X-ray diffraction analysis. The second harmonic generation were performed using KDP crystals before polishing, after laser beam polishing and after sandpaper polishing. The intensity of the light from the crystal by the laser beam polishing was the best of these three crystals.