Dependence of Linear Electro-Optic Effect and Dielectric Constant on Melt Composition in Lithium Niobate

Abstract

It has recently been reported by Hirano [Jap. J. Appl. Phys. 8,399 (1969) and J. Phys. Soc. Japan Suppl. 28, 90 (1970)] that the dc half‐wave voltage in lithium niobate increases appreciably with any departure from a melt stoichiometry (Li/Nb)_m=1.00. Our measurements of the low‐ and high‐frequency half‐wave voltages indicate no variation over the range of melt stoichiometries originally considered. We have also measured the effect of compositional variations upon the low‐ and high‐frequency dielectric constants and we find a smaller change and in the opposite sense from that reported by Hirano. We discuss the indirect evidence which argues against any special importance being attached to the particular composition (Li/Nb)_m=1.00. Theoretical estimates of the anticipated changes in the half‐wave voltages with composition support our experimental conclusions.