Anomalous broadband Floquet topological metasurface with pure site rings

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.