US Patent 11480729 Thermally compensated slot waveguide

A photonic integrated circuit includes a slot optical waveguide having an optical core with sub-wavelength slot therein that is partially filled with a first lower-index material having a negative thermo-optic coefficient. The slot may also include a second lower-index material having a positive thermo-optic coefficient. The relative volume of the first lower-index material within the slot may be configured to provide athermal or nearly-athermal operation. Example applications include integrated AWG MUX/DEMUX devices, Mach-Zehnder modulators, and micro-ring resonators or modulators implemented with silicon-based or silicon-nitride based slot waveguides with reduced sensitivity to temperature changes.