Abstract:
A waveguide mode expander couples a smaller optical mode in a semiconductor waveguide to a larger optical mode in an optical fiber. The waveguide mode expander comprises a shoulder made of crystalline silicon and a ridge made of non-crystalline silicon (e.g., amorphous silicon). In some embodiments, the ridge of the waveguide mode expander has a plurality of stages, the plurality of stages have different widths and/or thicknesses at a given cross section.
Abstract:
An optical, directional coupler has a first input, a second input, a first output, and a second output. The coupler is made with a shoulder disposed on a substrate and a first ridge and a second ridge disposed on the shoulder. The first ridge extends from the first input to the first output. The second ridge extends from the second input to the second output. The shoulder, the first ridge, and the second ridge taper to provide coupling and are modified to select a coupling ratio.