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

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.