BBO crystal growth in static and rotating heat fields of variable symmetry

Abstract

BBO crystals ((beta) -BaB2O4) exhibit unique nonlinear- and electro-optical properties, which provide their wide application in laser techniques. The growth of BBO is a technologically sophisticated procedure enabling the production of big high-quality single crystals. The growth of BBO crystals is performed with high-temperature melt-solution crystallization method, most commonly in the BaO-B2O3- Na2O ternary system. The typical effect of constitutional supercooling results from a high viscosity of the melt- solution and the fact that a growing BBO crystal shields the crystallizing melt, thus removing heat away from crystallization interface. The contribution considers the possibility of the improvement of crystal growth process via the change of heat field symmetry and its rotation. The symmetry of a static heat field reducing from Lvaries direct as to L3 results in stronger convection and, therefore, larger crystal. On the other side the permanent symmetry of a heat field -- static or rotating -- commonly provokes the formation of a quite big defect area in the central part of a grown boule with the signs of cell growth. To improve the convection in the central sub-crystal area we performed the BBO crystal growth process in a rotating heat field, which is free of the symmetry axis coinciding with the symmetry axis of the growth furnace/crucible. The experiments showed that the crystal with a defect-free central area can be successfully produced.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.