Structural and optical characterization of Er3+/Yb3+-doped LiNbO3

We report the dependence of the unit-cell parameters and the extraordinary and ordinary refractive indices of Er3+/Yb3+-codoped LiNbO3 crystals. Both properties depend in a non-monotonic manner on the Er3+/Yb3+ content. A sin gularity was observed at concentrations of 1.1 - 1.2 mol.% in the crystal ( 0.6 - 0.7 mol.% in the melt). In the same way the Er and Yb concentration i nfluences the periodically poled lithium niobate formation. The observed be havior of refractive indices and unit-cell parameters of Er3+/Yb3+-codoped LiNbO3 crystals could be explained in terms of the RE3+-ion concentration a ffecting the Li-vacancy concentration and the RE3+-ion positions in the cry stal.