US Patent 11181693 Polarization-insensitive directional couplers

Structures for a directional coupler and methods of fabricating a structure for a directional coupler. A first waveguide core has a first section, a second waveguide core has a second section laterally adjacent to the first section, a third waveguide core has a first taper, a second taper, and a third section longitudinally positioned between the first taper and the second taper, and a fourth waveguide core has a first taper, a second taper, and a fourth section longitudinally positioned between the first taper and the second taper. The fourth section is laterally adjacent to the third section, and the third section and the fourth section are positioned either over or under the first section and the second section.