Compact Tapers for Wire-to-Slot Fundamental Mode Coupling

We present a compact taper-based scheme for a wire-to-slot waveguide coupler in Silicon-on-Insulator platform. The phase matching between a wire and slot mode is achieved using a ~17.5 μm compact fabrication-tolerant multimode interference-based taper. We show a theoretical wire-to-slot coupling efficiency of 90 % and fabricate the devices to obtain a coupling of ~6.4 dB per coupler.