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Toroidal response due to strong near-field coupling in planar metamaterials (Conference Presentation)

The main research efforts in the metamaterials science are focused on achieving negative permittivity and permeability, as well as on effects such as superresolution, subwavelength guiding, enhancement of field localization, nanoantennas etc. At the same time, there is a wide range of interesting problems, beyond the issues of negative refraction. One of them is the problem associated with the excitation of toroidal response in metamaterials and the unusual phenomena associated with such response. In this paper, we demonstrate that, owing to the unique topology of the toroidal dipolar mode, its electric/magnetic field can be spatially confined within sub-wavelength, externally accessible regions of the metamolecules, which makes the toroidal metamaterials a viable platform for sensing, enhancement of light absorption and optical nonlinearities, and, especially, ingredient for qubits and quantum metamaterials. The metamolecules employed in the present study are planar conductive structures consisting of two symmetric split loops. The excited circular currents along the loops lead to a circulating magnetic moment and, as a result, to a toroidal moment. We note that the electric field is strongly localized in the splits of the loops and allows achieving the extremely high Q-factor of such types of resonators.