The effect of NaCl melt-additive on the growth and morphology of LiB3O5 (LBO) crystals

Abstract

The growth of nonlinear optical crystals of large size and excellent quality is of prime importance for frequency conversion applications. In the flux growth of LiB3O5 (LBO), the presence of extended BO3 and BO4 chain-like structures gives rise to highly viscous melts. As a consequence, mass transport is restricted and the depletion of material at the melt–crystal interface results in unstable hopper growth. The addition of small amounts of NaCl to the melt is effective in breaking BO4 bond chains. The resulting reduction in viscosity facilitates an increase in growth rate by up to a factor of 3. However, the incorporation of NaCl into the lattice may have an adverse effect on crystal quality. In the present study, LBO crystals of typical dimension 30×30×26 mm3 were grown by top-seeded solution from borate fluxes doped with 2 and 4 mol% NaCl, and without NaCl. Changes in growth and morphology are described as a function of melt dopant concentration. Laser damage threshold will be discussed in relation to the concentration of NaCl in the crystal.