Anomalous broadband Floquet topological metasurface with pure site rings

Abstract

Photonic and acoustic topological insulators exhibiting one-way transportation that is robust against defects and impurities are typically realized in coupled arrays of two-dimensional ring resonators. These systems have produced a series of applications, including optical isolators, delay lines, and lasers. However, the structures are complicated because an additional coupler ring between neighboring rings is needed to construct photonic pseudospin. A photonic anomalous Floquet topological insulator is proposed and experimentally demonstrated in the microwave regime. This improved design takes advantage of the efficient and backward coupling of negative-index media. The results contribute to the understanding of topological structures in metamaterials and point toward a unique direction for constructing useful topological photonic devices.