Dual-band toroidal-dipole-induced transparency in optical regime

Abstract

The interference between toroidal and electric dipoles in the optical regime is investigated in a metallic composite metastructure composed of a 12-fold double-bar and an upright rod. It shows that toroidal and electric dipoles can be simultaneously excited, exhibiting a plasmon analog of electromagnetically induced transparency (EIT) and suppressing the far-field radiation. By shifting the upright rod transversally, another transparency window emerges due to the asymmetry of the geometry, resulting in dual-band EIT-like behavior. The result not only contributes to the understanding of optical toroidal dipoles, but also creates the possibility of designing optical devices based on the dual-band EIT-like effect.