Effect of HfO₂-codoping concentration on the optical properties ofEr³⁺-Doped LiNbO₃

A series of Hf, Er co-doped LiNbO₃ crystals were grown by Czochralski technique with 1 mol% of Er₂O₃ and with 2, 4, 6 and 8 mol% of HfO₂, respectively. The optical damage resistance of Hf:Er:LiNbO₃ crystals was studied by the transmitted beam pattern distortion method. The optical damage resistance of Hf (6 mol%): Er:LiNbO ₃ crystals is about two orders of magnitude higher than that in Hf:Er:LiNbO₃. The X-ray power diffraction, the ultraviolet-visible absorption spectra and the infrared absorption spectrum were measured and discussed in terms of the spectrometric characterization and the defect structure of crystals. The results showed that with mild co-doping with HfO ₂, Er³⁺ substitutes Nb⁵⁺, whereas with heavy co-doping, a part of Er³⁺ substitutes Li⁺. The structure defects were discussed in this paper to explain the improvement of the optical damage resistance in the Hf:Er:LiNbO₃.