Crystalline/Amorphous Si Integrated Optical Couplers for 2D/3D Interconnection

The in-plane and interlayer waveguide-type couplers between crystalline Si and amorphous-Si:H wire waveguides, for 2D/3D hybrid-material integration are presented in this paper. The in-plane-type coupler achieves stable coupling between two waveguides by using tapers located at the tips of the waveguides. The interlayer-type coupler can connect two waveguides, despite an interlayer distance of 1 μm, with a simple process flow, by introducing a trident structure. An experiment was conducted in which the in-plane and interlayer-type couplers realized low coupling losses (coupling efficiencies) of 0.16 dB (96%) and 0.49 dB (89%) per coupler, respectively.