Locally Er-doped near-stoichiometric LiNbO₃ crystal for integrated optics

X- and Z-cut locally Er-doped near-stoichiometric LiNbO₃ crystals have been fabricated using two methods: direct vapor transport equilibration (VTE) treatment on congruent crystals coated with erbium (Er) metal, and a two-step process with standard thermal in-diffusion of Er metal followed by VTE treatment. Detailed studies on the crystalline phase, the Li composition, the diffusivity and the spectroscopic property of Er₃₊ ion, and the diffused surface roughness indicate that there is a limitation on the initial Er metal film thickness, and the near-stoichiometric Er:LiNbO ₃ crystals prepared by both methods are promising substrates for integrated optics applications.