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Bulk laser damage threshold of 2-in.-diam. MgO-doped LiNbO3 crystals grown using the Czochralski technique has been measured using a Q-switched Nd3+:LiYF4 laser. The threshold showed dependence on the crystal quality. The highest bulk laser damage threshold (14 J/cm2 at 1.053 μm wavelength with 1-ns pulse width) was obtained in the LiNbO3 crystal doped with 1 mol % of MgO. The lowering of bulk laser damage threshold was observed in the crystals doped with MgO at more than 3 mol %. These crystals contained the local aggregations of MgO which increased the scattering centers and decreased the transparency.

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We report on the fabrication of a first-order periodically inverted domain structure in LiTaO3 and LiNbO3 for quasi-phase-matched devices using proton exchange with one-directional heating. First-order periodically inverted domains with a 3.2 μm period and more than 40 μm depth were formed beyond the proton exchanged region. This domain inversion took place during the proton exchange process, far below the Curie temperatures. Taking advantage of these deep domains, we demonstrated second-harmonic generation without fabricating a channel waveguide.

Clear and transparent 2-inch diameter undoped and MgO-doped LiTaO3 single crystals with few Fe impurities have been grown by the conventional Czochralski method from a congruent melt. The optical damage resistance of undoped LiTaO3 has been characterized by the measurement of photoinduced birefringence change and is lower than that of commercially available LiNbO3, which is not consistent with the previously reported data in the literature. In addition, doping of a few mol% MgO further improved the optical damage resistance, transmission in the visible light region, and crystal decolorization, and produced a favorable shift of absorption edge toward shorter wavelengths for lithium tantalate. These are important advantages when considering shorter- wavelength accessibility and high conversion efficiency in second-harmonic- generation devices.