Effect of charge mixture preparation technology on the physicochemical and optical properties of LiNbO3:Mg crystals

Abstract

LiNbO₃:MgO crystals, representing important materials for nonlinear optics, laser optics, integrated optics, and optical electronics owing to their high resistance with respect to optical damage, are studied. The crystals of LiNbO₃:MgO were grown from a granulated charge mixture of lithium niobate synthesized using homogeneously doped Nb₂O₅:Mg precursors of different origin. The effect of organic substances used in the technology of lithium niobate charge mixture on the properties of LiNbO₃:MgO single crystals is studied. It is found that the physicochemical and optical characteristics of LiNbO₃:MgO crystals grown from charge mixtures synthesized from Nb₂O₅:Mg precursors obtained using organic solvents and without them differ to a considerable extent. It is suggested that the difference in the properties of LiNbO₃:MgО crystals of different origin is caused by change in the structure of the ion complexes in the melt owing to the presence of traces of organic impurities. Change in the structure of ion complexes in the melt leads to change in crystallization mechanisms and, accordingly, in the chemical composition and the properties of LiNbO₃:MgO crystals. Furthermore, it is shown that the use of homogeneous doping methods as opposed to the method of direct doping provides the distribution coefficient K_eef > 1. That is, the method of homogeneous doping allows one to introduce a substantially greater concentration of an impurity element in the LiNbO₃:MgO crystal compared with the direct method for doping the charge mixture at the same impurity concentration in the starting material.