Diffusion barrier layer in lithium niobate-containing photonic devices

An electro-optic device, comprising:

• a waveguide including a thin film electro-optic layer, the thin film electro-optic layer including lithium and including a plurality of patterned structures, each of the plurality of patterned structures having a plurality of surfaces, the plurality of surfaces including a bottom surface, a top surface, and a plurality of sidewalls, the waveguide including an upper waveguide structure, a lower waveguide structure, and a sidewall waveguide structure, the waveguide being on a substrate, the thin film electro-optic layer having a thickness not exceeding three micrometers;
• a lithium barrier structure covering at least a portion of the plurality of surfaces, wherein the lithium barrier structure includes an upper lithium barrier structure, a lower lithium barrier structure, and a sidewall lithium barrier structure, and
• a plurality of electrodes in proximity to a portion of the waveguide, wherein the upper surface of the waveguide is covered by the upper lithium barrier structure, wherein the bottom surface of the thin film electro-optic layer is covered by the lower lithium barrier structure, wherein at least one sidewall of the plurality of sidewalls of the waveguide is covered by the sidewall lithium barrier structure, and wherein the sidewall lithium barrier structure has an L shape.