Locally er-doped near-stoichiometric LiNbO₃ Crystals prepared by standard er diffusion and post-VTE treatment

The feasibility of preparing locally Er-doped near-stoichiometric (NS) LiNbO₃ crystals for integrated optics applications is demonstrated by a two-step process with standard diffusion (1130°C/154 h) of Er metal followed by vapor transport equilibration (VTE) treatment under three different conditions of 1135°C/22 h, 1115°C/50 h, and 1125°C/60 h. Detailed studies on the crystalline phase, Li composition, diffused surface roughness, and emission characteristics of Er³⁺ ions indicate that there is an upper limit on the initial Er metal film thickness: ∼20 nm for an X-cut crystal and ∼30 nm for a Z-cut crystal. When the initial Er film thickness is below this limit, the post-VTE does not induce formation of ErNbO₄ precipitate and the diffused surface retains high quality with a root mean square roughness - content in crystal, slight lengthening of lifetime and slight narrowing of linewidth of Er³⁺ emission at 1530 nm. © 2009 The American Ceramic Society.