INFLUENCE OF THE DAMAGE RESISTANT IMPURITIES ZN AND MG ON THE UV-EXCITED LUMINESCENCE IN LINBO3

In LiNbO3 the intrinsic uv-excited luminescence in the visible is controlled by the stoichiometry of the crystal and doping with Mg or Zn. Either the increase of the Li/Nb ratio or incorporation of Mg or Zn lead to the same change of the emission bandshape and intensity. The emission increases with increasing impurity concentration and tends to saturate above the values of about 5 mol% Mg or 7 mol% Zn. These are 'thresholds' corresponding simultaneously to a drastic reduction of the photorefraction. The luminescence lifetimes are temperature dependent and again are governed by impurity concentrations. The results are discussed in terms of the site-antisite model regarding Nb(Li) and Nb(Nb) centers to be responsible for the intrinsic luminescence and its kinetics in LiNbO3, that means a substitution for Nb(Li) by Mg or Zn.