Growth and photo-damage resistance of Hf:LiNbO3 crystals

Hf:LiNbO3 (Hf:LN) crystals doped with 2% (in mole, the same below), 4% and 4.5% HfO2 in congruent LN were grown by the Czochralski method. The optical homogeneity and the infrared spectra of the Hf:LN crystals were researched. Hf:LN waveguide substrate was prepared by the proton transfer method. The photo-damage threshold of the Hf:LN waveguide substrate was measured by the holographic method. The results show that the Hf:LN crystals possess good optical quality. The OH-absorption peaks of 4% Hf:LN crystal and 4.5% Hf:LN crystal shift from 3482 cm-1 of LN crystal to 3488 cm-1. The photo-damage threshold of 4% Hf:LN and 4.5% Hf:LN crystals increase one order of magnitude compared with that of LN crystal, and doping with 4% Hf4+ concentration reaches the threshold concentration in Hf:LN crystal. The mechanism of absorption peaks movement and the photo-damage threshold increment of Hf:LN crystals are discussed.