Growth and characterization of MgO doped near stoichiometric LiNbO3 crystals as a new nonlinear optical material

Nondoped and MgO-doped LiNbO3 single crystals of 30 mm in diameter and 25-30 mm in length were grown by the top-seeded solution growth method. The solution with [Li]/[Nb] ratio of 1 contained K2O component of 10.6 mol% (7 wt%), MgO of different concentrations was used to dope the solution. As-grown crystals were transparent, void-free and almost free from potassium contamination. The crystal grown without MgO-doping exhibited a Curie temperature of 1193 degrees C, indicating that the crystal composition was considerably close to stoichiometry. The MgO-doped crystals grown from the above solution showed larger [Li]/[Nb] ratios (that is, closer to stoichiometry) than the crystals grown from the congruent composition melt doped with MgO of the same doping levels. The MgO-doped crystals with near stoichiometric composition showed a shift in absorption edge towards shorter wavelength, an increase in Curie temperature, and four orders of magnitude increase in photorefractive damage resistance compared to nondoped crystals grown from the congruent melt by the conventional Czochralski method. (C) 2000 Elsevier Science B.V. All rights reserved.