Doping mechanism of optical-damage-resistant ions in lithium niobate crystals

The doping mechanism of optical-damage-resistant ions (Mg²⁺, Zn²⁺, In³⁺, Sc³⁺, Hf⁴⁺, and Zr⁴⁺) in the lithium niobate crystallographic frame is quantitatively studied from the chemical bond viewpoint. Calculated results show that optical-damage-resistant ions have a strong interaction with the lithium niobate matrix, which is quantitatively evaluated by the deviation between normal and calculated valence states and the global instability index. All optical-damage-resistant ions first substitute Nb_Li and then Li ions, they change their dopant occupancies from Li to Nb sites at the same global instability index value 0.1055. On the basis of such a quantitative interaction, the doping mechanism of these ions is finally derived. Furthermore, a criterion in searching for new optical-damage-resistant ions is also proposed.