Growth of beta-BaB2O3 single crystals for frequency converters of optical radiation

摘要

Abstract: Single crystals $beta@-BaB$-2$/O$-4$/ (BBO) are new perspective nonlinear-optical material used for development of laser sources tunable in wide spectral range from near IR to UV. It is well known that BBO single crystals cannot be grown from their own melt because of formation of $alpha@- phase of BaB$-2$/O$-4$/ at melting point of 1095$DGR@C. Therefore the solution-melt (flux) technique is used for growth of low-temperature $beta@-BaB$-2$/O$-4$/ phase (temperature of $alpha $YLD $beta phase transition is 925$DGR@C). This method is applied still quite seldom because of high labor-consuming. BBO single crystals were grown by top-seeded solution growth technique with high temperature gradient with simultaneous decrease of temperature. The main difficulties of the growth of BBO single crystals are related to high viscosity, tendency to stratifying and vitreous formation, incongruent evaporation of solution-melt, and possibility of simultaneous co- crystallization both $alpha@- and $beta@-phases from the supercooled solution-melt. Any of them result in formation of various growth defects with concentrations depended on peculiarities of technological conditions.!4