Fabrication of Titanium-In-Diffused Lithium Niobate Optical Waveguides by Laser Annealing at 10.6 μm

Abstract

The most common method for fabricating high quality planar and channel waveguides in electrooptic lithium niobate is titanium in-diffusion.1 This process typically involves uniform heating, in a furnace, of polished lithium niobate single crystal substrates on which dense, thin titanium metal films have been deposited. The process, nowadays, is normally conducted for 5-6 hours in moistened oxygen2 at 1000°C. As the diffusion furnace is heated to 1000°C, or during an intentional pre-soak at 600°C, the titanium film oxidizes to titanium dioxide. This oxide precursor then reacts with the crystal surface layers in a complex mechanism culminating in the diffusive incorporation of titanium ions within the lithium niobate lattice.