Investigations of the OH- absorption bands in congruent and near-stoichiometric LiNbO3:Hf crystals

OH- absorption bands of both congruent and near-stoichiometric LiNbO3: Hf crystals were investigated. The abrupt blueshift of OH- absorption bands was found between the doping levels of 2 and 2.5mol% in the congruent crystals, which confirms the exact optical-damage threshold for Hf doping. The absorption difference of OH- bands between the congruent and near-stoichiometric crystals shows that after Li incorporation H+ ions no longer prefer the sites of 3500cm(-1). Moreover, with the increase of Hf doping in the near-stoichiometric crystals, H+ ions were found to gradually transfer to the sites of 3489cm(-1). These results are explained by the breakdown of the association of Hf-Nb(-) and H+ ions and the subsequent redistribution of H+ ions around Hf-Li(3+) ions in V-Li(-)-deficient lattice. Additionally, the link between the intrinsic defects and how they influence the optical-damage threshold upon adding Hf was discussed in detail. Copyright (c) EPLA, 2010