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More than 300mW of 355nm generation was confirmed by cascaded configuration from 1064nm pulsed laser by using PP-LBGO (LaBGeO5) without walk-off. Measured temperature tolerances are 8.4 K-cm, which is almost double of Type-II LBO.

We report that nearly stoichiometric LiNbO3 doped with small amount of MgO exhibit better material properties than conventional congruent crystals. Improvements are demonstrated with high photorefractive damageresistance at 532 nm to intensities as much as 8MW/cm2, low 180° ferroelectric domain switching field of 3.4 KV/mm, short absorption edge of 302 nm, and small scattering losses.

We grew near stoichiometric LiTaO3 crystal from a Li-rich melt using a novel double crucible Czochralski method. The ferroelectric domain shape and domain wall smoothness were compared between the conventional and near stoichiometric LiTaO3 crystals. It turned out that the domain shape under the electric field at room temperature strongly depended on the densities of nonstoichometric defects. The domain shape in the conventional LiTaO3 is basically triangular while it is hexagonal in the stoichiometric LiTaO3. The sides of hexagon in the stoichiometric LiTaO3 are perpendicular to the crystallographical X axes, that is, parallel to the X faces. Therefore, considerably smooth domain walls can be obtain in the stoichiometric LiTaO3 when the periodical domain structure is designed as each domain elongates along the Y axis. This result is promising a great improvement by using stoichiometric LiTaO3 in fabricating quasi-phase matching wavelength conversion devices with high performances.

Photorefractive damage and green-induced IR absorption of LiNbO3 single crystals have been investigated as a function of [Li]/[Nb] and MgO concentrations. Nearstoichiometric LiNbO3 crystals doped with small amount of MgO (> 0.78 mol.%) exhibit neither photorefractive damage at 532 nm to intensities of as much as 8 MW/cm2 nor increase of IR absorption with an irradiation of 3.5 KW/cm2 of green light. This remarkable decrease of photorefraction and green-induced IR absorption in MgO-doped LiNbO3 can be attributed to the elimination of intrinsic defects of Nb at Li site by their substitution of Mg at Li site.