The peculiar impurity concentration ranges in damage-resistant LiNbO₃crystals doped with Mg, Zn, In and Sn

We report on a comparative study of the optical damage-resistant impurities Mg and Zn, as well as In and Sc in LiNbO3. In LiNbO3 doped with these ions a certain behavior of physical properties (e.g., the shape of OH stretch mode bands, phase-matching temperatures of optical frequency doubling, etc.) on the impurity concentration is observed. The corresponding (‘threshold’) concentrations are about 5–7 mol.% for the divalent cations Mg and Zn and only 1 mol.% for the trivalent In and Sc. The results are discussed assuming that these ions incorporate on Li-sites thus removing the intrinsic defect NbLi from the lattice.