Broken Symmetry Dielectric Resonators for High Quality Factor Fano Metasurfaces

We present a new approach to dielectric metasurface design that relies on a single resonator per unit cell and produces robust, high quality factor Fano resonances. Our approach utilizes symmetry breaking of highly symmetric resonator geometries, such as cubes, to induce couplings between the otherwise orthogonal resonator modes. In particular, we design perturbations that couple bright dipole modes to dark dipole modes whose radiative decay is suppressed by local field effects in the array. Our approach is widely scalable from the near-infrared to radio frequencies. We first unravel the Fano resonance behavior through numerical simulations of a germanium resonator-based metasurface that achieves a quality factor of similar to 1300 at similar to 10.8 pm. Then, we present two experimental demonstrations operating in the infrared (similar to 1 mu m): a silicon-based implementation that achieves a quality factor of similar to 350; and a gallium arsenide-based structure that achieves a quality factor of similar to 600, the highest near-infrared quality factor experimentally demonstrated to date with this kind of metasurface. Importantly, large electromagnetic field enhancements appear within the resonators at the Fano resonant frequencies. We envision that combining high quality factor, high field enhancement resonances with nonlinear and active/gain materials such as gallium arsenide will lead to new classes of active optical devices. near-