For high perfection of structure in Nd-YAG laser crystals grown by the Czo-chralski method, the dislocation density of the crystals must be decreased. Research study seems to indicate that the direction of dislocation propagation is perpendicular to the solid-liquid interface. In crystals grown with a Convex solid-liquid interface, the low dislocation density is due to spreading out of the dislocations in the central part towards the surrounding areas and the edges. Hence, by applying suitable technology i. e. intentionally changing the shape of the solid-liquid interface, we can obtain crystals in which not only the dislocations are decreased, but also the facets are eliminated.
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