Excitation of electric toroidal dipole resonance and design of chiral materials

Abstract

Toroidal multipole is a particular type of current excitation and is currently the focus of nanophotonics and metamaterials research. However, the excitation of toroidal dipoles is a challenging task because of their low scattering power. In this paper, using vertically incident polarized light, the Electric toroidal dipolar (ETD) resonance response can be successfully excited by a reasonable arrangement of thin metal wires and long metal arms without the need for a complex metal ring structure. The results indicate that the toroidal dipole moment G cannot be ignored at 0.61 THz and 0.65 THz. By rearranging the metamaterial structure that excited the ETD response, the multi-band circular dichroism, and negative refraction are successfully realized. The proposed structure can be applied in many fields, such as the research of toroidal multipoles, left-handed materials, and circularly polarized converters.