Demonstration of toroidal metasurfaces through near-field coupling of bright-mode resonators

Abstract

Abstract Bright-mode resonances are not well-acknowledged for inducing mode hybridizations. However, we demonstrate that multiple bright resonators coupled through electromagnetic fields can induce resonance mode hybridizations. Although one of the hybridized modes shows parallel magnetic moments, the other demonstrates anti-parallel magnetic moments leading to magnetic toroidal resonances. The excitation of toroidal modes usually demands complex structures and/or bright–dark-mode interactions. However, in this study, we employ only bright resonators to excite toroidal modes. Unlike bright–dark-mode coupling, exclusive bright-mode resonance coupling enables larger free-space energy to merge into the metasystem, which leads to stronger energy confinement in the metasurface array.