On possible existence of a new Er centres in LiNbO3:Er, Tm

Electron paramagnetic resonance experiments have been carried out on Congruent lithium niobate (LiNbO3) single crystal weakly doped with Er (0.2 wt.%) and codoped with Tm (0.3 wt.%). The EPR lines originating from both the Er-167(3+) ions, with a hyperfine structure, as well as from the Er-even(3+) ions, are identified. Angular dependence of the EPR lines has allowed distinguishing the presence of several non-equivalent Er3+ centres with the lowest (C-1) symmetry. Additionally, some spectral features may indicate the presence of new Er3+ centres with possibly cubic symmetry, however, an alternative explanation is also considered. The model of Er3+ centres and the effects of stoichiometry and codoping on the spectroscopic properties of erbium ions in LiNbO3 crystal are considered. (C) 2008 Elsevier B.V. All rights reserved.