Investigations of the OH− absorption bands in congruent and near-stoichiometric LiNbO3:Hf crystals
School of Material Science and Engineering, Hebei University of Technology - Tianjin 300130, China
2 Department of Physics, Tianjin Urban Construction Institute - Tianjin 300384, China
3 The MOE Key Laboratory of Weak-Light Nonlinear Photonics, Nankai University - Tianjin 300457, China
Accepted: 2 August 2010
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 2.5 mol% 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 3500 cm−1. Moreover, with the increase of Hf doping in the near-stoichiometric crystals, H+ ions were found to gradually transfer to the sites of 3489 cm−1. These results are explained by the breakdown of the association of HfNb− and H+ ions and the subsequent redistribution of H+ ions around HfLi3+ ions in VLi−-deficient lattice. Additionally, the link between the intrinsic defects and how they influence the optical-damage threshold upon adding Hf was discussed in detail.
PACS: 61.72.-y – Defects and impurities in crystals; microstructure / 77.84.Ek – Niobates and tantalates / 78.30.-j – Infrared and Raman spectra
© EPLA, 2010