Laterally coupled hexagonal micropillar resonator add-drop filters in silicon nitride

We report the first laterally coupled hexagonal micropillar resonator add-drop filters in silicon nitride. Our experiment reveals waveguide-coupled resonances of six-bounce ray orbits in the hexagonal microcavity. By tuning the submicrometer waveguide width, we demonstrate simultaneous optimization of the coupling efficiency and the resonance Q value. We attribute the optimum waveguide width to the near k-vector matching between the input- and output-coupled waveguide fundamental mode and the cavity six-bounce modes that are coherently coupled along the resonator flat sidewalls.