Guided wave device and method of fabrication thereof

摘要

A method for co-diffusing titanium and aluminum into a single-crystal lithium niobate substrate and guided wave devices produced therefrom are provided. Titanium diffused into the substrate forms a light guiding region. A layer of aluminum deposited over the light guiding region and diffused into the substrate buries the light guiding region below the substrate surface. In an alternate embodiment, a layer of aluminum forms a mode shaping region which surrounds the light guiding region on two sides. The mode shaping region has ordinary and extraordinary indices of refraction less than the substrate such that mode mismatch between a device fabricated thereby and an externally coupled fiber is reduced. The aluminum can be diffused into LiNbO3 at a much lower temperature without affecting diffused titanium guides. Preferably, the titanium diffusion occurs at about 1000 DEG to about 1100 DEG C. while further aluminum diffusion occurs at a lower temperature in the range of about 900 DEG to 950 DEG C.