Compositional Uniformity in Growth and Poling of Large-Diameter Lithium Niobate Crystals

Reprinted with permission from P.F. Bordui, R.G. Norwood, D. H. Jundt, and M. M. Fejer, Journal of Applied Physics, 71, 875-879, (1992). American Institute of Physics.

Reprinted from Journal of Crystal Growth, 113, Bordui, P.F., Norwood, R.G., Bird, C. D., and Calvert, G. D., Compositional uniformity in growth and poling of large-diameter lithium niobate crystals, 61-68, 1991, with permission from Elsevier Science.

Abstract

An experimental study was performed of compositional uniformity in growth and poling of large-diameter lithium niobate crystals. Crystal compositions were characterized through Curie temperature measurement and phase-match ttemperature measurement for non-critical 1.06µm frequency doubling. Methods were esatablished and tested for preparing crystal growth melts of controlled stoichiometry specifiable to within 0.01 mol% Li₂O. A previously unreported congruent composition value of 48.38± 0.015 mol% Li₂O was determined. Near the congruent composition, a strong influence was observed of melt stoichiometry on the domain structure of as-grown crystals. The effects of post-growth poling on compositional distribution were studied. Effective poling conditions having unmeasurable influence on crystal composition were established. Use of a congruent melt was observed to enable growth of clear uncracked crystals representing melt fractions as large as 98%. Crystals representing 85% melt fractions were routinely grown having compositional uniformity of ± 0.003 mol% Li₂O. Lithium niobate crystalline material produced through the combination of congruent growth and preferred poling conditions was observed to enable improved acoustical and optical device performance.