Locally Er-Doped Near-Stoichiometric LiNbO^sub 3^ Crystals Prepared by Standard Er Diffusion and Post-VTE Treatment

The feasibility of preparing locally Er-doped near-stoichiometric (NS) LiNbO... 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 Er... 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 ErNbO... precipitate and the diffused surface retains high quality with a root mean square roughness