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 cont rolled by the stoichiometry of the crystal and doping with Mg or Zn. E ither the increase of the Li/Nb ratio or incorporation of Mg or Zn lea d to the same change of the emission bandshape and intensity. The emis sion increases with increasing impurity concentration and tends to sat urate above the values of about 5 mol% Mg or 7 mol% Zn. These are 'thr esholds' corresponding simultaneously to a drastic reduction of the ph otorefraction. The luminescence lifetimes are temperature dependent an d again are governed by impurity concentrations. The results are discu ssed in terms of the site-antisite model regarding Nb(Li) and Nb(Nb) c enters to be responsible for the intrinsic luminescence and its kineti cs in LiNbO3, that means a substitution for Nb(Li) by Mg or Zn.