US Patent 11927801 Stacked waveguide cores with tunable phase delay

Structures for a waveguide core and methods of forming such structures. The structure comprises a stacked waveguide core including a first waveguide core and a second waveguide core stacked with the first waveguide core, and a layer adjacent to the stacked waveguide core. The layer comprises a material having a refractive index that is variable in response to a stimulus.