US Patent 8948555 Skew waveguide directional coupler

Embodiments of the invention describe a skew directional coupler for a plurality of waveguides. Said coupler includes a first waveguide on a first plane and a second waveguide on a second plane separate from the first plane. In embodiments of the invention, the first waveguide is disposed on top of the second waveguide to form an overlapping region of a segment of the first waveguide and a segment of the second waveguide, wherein an optical axis of the segment of the first waveguide is horizontally skew to an optical axis of the segment of the second waveguide, and wherein light is to be passively transmitted between the first and second waveguide segments via mode hybridization.