Efficient and tunable strip to slot fundamental mode coupling.
We present a novel photonic wire to slot waveguide coupler in SOI. The phase matching between a wire and slot mode is achieved using a mode transformer. The architecture consists of a balanced 50/50 power splitter and a tunable phase matched taper combiner forming a slot waveguide. We show a theoretical wire to slot coupling efficiency of 99 is achievable and experimentally, we demonstrate a coupling efficiency of 99 in the 1550 nm band. Based on the coupling scheme, we also show excitation of a slot mode in a slotted ring resonator and verified the excitation through the thermo optic response of the rings. We show a nearly athermal behaviour of a PMMA filled slot ring with a thermo optic response of 12.8 pm/degC compare to 43.5 pm/degC for an air clad slot waveguide.
Optics express