Rearrangement of rare earth defects under domain inversion in LiNbO ₃

Using high resolution excitation-emission spectroscopy we investigated the changes occurring in the optical transition of Er³⁺ ions in LiNbO₃ during inversion of the ferroelectric axis. In stoichiometric LiNbO₃ we find that a drastic reconfiguration among the different defect sites takes places favoring those centers which have already been dominant in the as-grown sample. The reconfiguration is attributed to changes in the arrangement of the local charge compensators. Furthermore, we find a small shift of the emission transition energy, which is consistent with an increase of the intrinsic electric field. These findings make the Er₃₊ ions very suitable probes for 3D imaging of domain structures and for in-situ studies of the dynamics of the domain inversion processes and the defect/domain wall interaction.