Dielectric Metamaterials with Toroidal Dipolar Response
  Toroidal multipoles are the terms missing in the standard multipole expansion; they are usually overlooked due to their relatively weak coupling to the electromagnetic fields. Here we propose and theoretically study all-dielectric metamaterials of a special class that represent a simple electromagnetic system supporting toroidal dipolar excitations in the THz part of the spectrum. We show that resonant transmission and reflection of such metamaterials is dominated by toroidal dipole scattering, the neglect of which would result in a misunderstanding interpretation of the metamaterials macroscopic response. Due to the unique field configuration of the toroidal mode the proposed metamaterials could serve as a platform for sensing, or enhancement of light absorption and optical nonlinearities. 
Alexey A. Basharin, Maria Kafesaki, Eleftherios N. Economou, Costas M.   Soukoulis, Vassili A. Fedotov, Vassili Savinov, Nik...
physics.optics