Patent ID: 8625942

Claim:
An apparatus comprising: a silicon-based rib waveguide integrated on a semiconductor substrate including a silicon-on-insulator (SOI) substrate, the rib waveguide to have a first waveguide mode in a direction parallel to a plane of the semiconductor substrate, the first waveguide mode to be vertically constrained by a thickness of the rib waveguide and a thickness of the semiconductor substrate, the first waveguide mode to exist in the rib waveguide and semiconductor substrate vertically below the rib waveguide; a silicon-based grating coupler integrated on the semiconductor substrate, the grating coupler having multiple vertical fins periodically spaced in a same plane as the rib waveguide, each vertical fin being substantially perpendicular to a direction of the first waveguide mode, the grating coupler to have a second waveguide mode in a direction parallel to a plane of the semiconductor substrate, the second waveguide mode to be vertically constrained by a second thickness at least ten percent smaller than the thickness of the rib waveguide; and a tapered edge tapering the rib waveguide toward the grating coupler, the tapered edge to focus light to convert from the first waveguide mode to the second waveguide mode.