Low-loss resonant modes in deterministically aperiodic nanopillar waveguides

Quasiperiodic Fibonacci-like and fractal Cantor-like single- and multiple-row nanopillar waveguides are investigated theoretically by employing the finite-difference time-domain method. It is shown that resonant modes of the Fibonacci and Cantor waveguides can have a Q factor comparable with that of a point-defect resonator embedded in a periodic nanopillar waveguide, while the radiation is preferably emitted into the waveguide direction, thus improving coupling to an unstructured dielectric waveguide located along the structure axis. This is especially so when the dielectric waveguide introduces a small perturbation in the aperiodic structure, breaking the structure symmetry while staying well apart from the main localization area of the resonant mode. The high-Q factor and increased coupling with the external dielectric waveguide suggest using the proposed deterministically aperiodic nanopillar waveguides in photonic integrated circuits.