Compositional Homogeneity and Optical Properties of Stoichiometric Lithium Niobate Crystals of Various Geneses

Abstract

It is shown that the method of high temperature top-seeded solution growth (HTTSSG) can be used to obtain near stoichiometric LiNbO₃ crystals from a congruent melt with the addition of 6.0 wt.% of the K₂O flux. The structure of complex defects containing OH⁻ groups in these crystals is close to those in stoichiometric crystals grown from a melt containing ∼ 58.6 mol.% of Li₂O. However, the former are significantly superior to the latter in terms of total optical and structural homogeneity. The obtained crystals are studied using laser conoscopy, photoinduced light scattering, measuring the fundamental absorption edge, IR absorption spectroscopy in the region of OH⁻ stretchings, Raman spectroscopy in the region of two-particle states of acoustic phonons with zero total wave vector.