Z-Shaped toroidal dipole planar terahertz metasurfaces

Abstract

We proposed and fabricated a Z-shaped toroidal dipole terahertz metasurfaces, consisting of two incomplete U-shaped split rings, and the two incomplete U-shapes are rotationally symmetric with respect to the Z-axis. The effects of the structural parameters on the electromagnetic characteristics of toroidal resonances are investigated via simulation and experiment. The mechanism of toroidal dipole resonance is studied deeply by establishing an LC resonance model and calculating the multipoles scattering energy. The capacitance was highly depended on the value of lx, and the inductance was determined by the value of ly. Hence, the red shift was observed as the increasing of ly/lx. The resonant frequency of the toroidal dipole resonance is red shifted, as the ly/lx of the metallic pattern increases. The tunability of toroidal dipole resonant frequencies explores the interaction of toroidal multipoles with terahertz wave that could have extensive applications in the terahertz functional devices.