High optical damage resistance of near stoichiometric LiNbO/sub 3/ crystals with low level MgO doping

Abstract

Summary form only given. MgO doped LiNbO/sub 3/ single crystals were grown by the top seeded solution. The solution with [Li]/[Nb] ratio of 1 contained K/sub 2/O component of 11 mol%. MgO of different concentrations was doped into the solution. As-grown crystals were almost free from potassium contamination, transparent, void-free and single-domain nature. The crystal grown without MgO doping exhibited a Curie temperature of 1192/spl deg/C, indicating that the crystal composition was considerably close to stoichiometry. The composition of MgO doped crystals grown from the above solution showed larger [Li]/[Nb] ratios (that is, close to stoichiometry) than the crystals grown from the congruent composition melt doped with MgO of the same doping levels. Optical damage resistance was characterized by observing the transmitted laser beam profile with cw Nd:YAG SHG laser irradiation. Non-doped crystal shows very strong beam distortion even at the beam intensity of 64 kW/cm/sup 2/. On the other hand, stoichiometric (1.8 MgO mol%) crystal shows no beam distortion even at the beam intensity of 8 MW/cm/sup 2/. Doping with MgO increases the optical damage resistance by at least 4 orders of magnitude compared with non-doped crystal. In the case of MgO doping, a heavy doping level such as 5 mol% is required for increasing the optical damage resistance. However, MgO doped crystal shows the similar optical damage resistance at lower doping level as 1.8 mol%.