Some multi-component photorefractive crystals exhibit wide variations in their properties associated with the nonstoichiometry of the constituent cations. In order to grow single crystals with high quality and high homogeneity under nonstoichiometry control, a double crucible Czochralski method has been developed. In this method, the melt was divided into two parts by a double structure (two chamber system) crucible. The crystal was grown from the inner melt, and a powder with the same composition as the growing crystal was supplied to the outer melt. The powder was supplied continuously and smoothly at the rate of weight increase of the growing crystal. This rate was automatically controlled to match the weight increase of the growing crystals as monitored by a load cell. As an example, LiNbO3 single crystals with a composition close to stoichiometric were grown, and their photorefractive properties were compared with those of Nb-rich congruent LiNbO3 crystal. As the result, it turned out that the stoichiometric LN crystal exhibited higher efficiency and faster responsivity than the congruent crystal.
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