Toroidal dipole response in the individual silicon hollow cylinder under radially polarized beam excitation

The toroidal dipole (TD) has attracted growing attention due to its unique properties. Here, we propose and demonstrate almost pure TD resonance in the visible region in a silicon hollow cylinder. The enhanced optical coupling to TD resonance is implemented using a focused radially polarized beam illumination matching, well-designed individual silicon nanostructure resonator. The polarization of the longitudinal electric field in the silicon hollow cylinder that breaks space-inversion symmetry is critical to the formation of enhanced TD resonance. Additionally, the pure TD resonance can be achieved in a wide spectral range by tuning the geometrical parameters of the structure. The proposed pure TD resonator may provide potential applications in the local enhancement of electromagnetic fields and the design of all-dielectric nanoantennas.