Patent ID: 7217585

Claim:
A method for fabricating and using a waveguide, comprising the steps of preparing two waveguide precursor pieces, each waveguide precursor piece comprising a single-crystal substrate made of an oxide substrate material and having a coating face with a substrate crystallographic direction lying in the coating face, and an epitaxial coating layer of an oxide coating material on the coating face of the substrate, wherein the oxide substrate material and the oxide coating material are different, wherein the oxide substrate material comprises yttrium as a substrate-material cation and the oxide coating material comprises a coating-material cation selected from the group consisting of ytterbium, thulium, erbium, and holmium; placing the two substrates together with their coating layers in contact and with their substrate crystallographic directions parallel, to form a precursor structure; and heating the precursor structure to an elevated temperature, so that the coating layers bond together, and the coating materials and the substrate materials interdiffuse to form the waveguide having an interdiffused region, and thereafter cooling the waveguide to room temperature.