| 摘要 |
PROBLEM TO BE SOLVED: To improve an optical polishing method in such a manner that the flaws and dents of a polished surface may be decreased and the accuracy of surface roughness improved by optically polishing crystals for a wavelength conversion element by using a polishing material consisting of zirconia powder having a specific particle size. SOLUTION: The crystals for the wavelength conversion element are optically polished by using the polishing material consisting of the zirconia powder having the particle size not over 1μm and larger than 0.2μm. Namely, the particles 7 of 0.5μm in the particle size of the zirconia is large in r of the particles and are, therefore, small in the curvature of the particles exposed on the surface of pitch and since the accuracy of the surface roughness of a polishing plate is improved, the accuracy of the surface roughness of the polishing plate is improved as well. If the r of the zirconia is made further as finer as 0.2μm, the increase in the ruggedness of the surface of the polishing plate is resulted and the conversely degraded surface roughness is resulted. The probability of the occurrence of the flaws and dents by the flocculation of the particles with each other at the particle size attaining 1μm increases and, therefore, 0.5μm is the optimum particle size of the polishing material.
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