Fano resonance induced by the toroidal moment in cylindrical metallic meta-structures

Fano resonance is a kind of resonant phenomenon which manifests an asymmetric line-shape. Here, the Fano-type spectra of scattering are found in a coaxial cylindrical metallic meta-structure, both in the microwave and optical regime. It is found that the peak of Fano resonance is mainly contributed from the toroidal dipole, whereas the dip is due to the destructive interference of the electric and toroidal dipole modes. At the peak of the Fano resonance, the magnetic field shows a 'vortex-like' configuration at the gap of metallic structure and the corresponding magnitude can be enhanced remarkably. This toroidal-based Fano resonance in the proposed meta-structures may find potential applications in nanophotonics, such as optical sensing, spectral engineering, etc. (paper)