Microwave toroidal dipolar response in an asymmetric planar metamaterial

Abstract Toroidal multipoles are the third type of multipoles which are fundamentally different from conventional electric multipoles and magnetic multipoles. The implementation of toroidal multipoles is hard since its energy is too low to be discovered. This paper proposes a simple planar metamaterial to achieve an often ignored toroidal dipolar response in the microwave band. The metamaterial is designed with a special asymmetric arrangement of asymmetric U-ring resonators to attain a toroidal resonance with high quality factor at 13.5 GHz. Its toroidal nature can be verified by calculated scattered power by multipoles, magnetic field and the surface current. The presented planar metamaterial owns toroidal resonance with high quality factor and it can be applied in the field of antennas, photonics, sensing and energy.