Toroidal dipole excitations in metamolecules formed by interacting plasmonic nanorods

Abstract

We show how the elusive toroidal dipole moment appears as a radiative excitation eigenmode in a metamolecule resonator that is formed by pairs of plasmonic nanorods. We analyze one such nanorod configuration - a toroidal metamolecule. We find that the radiative interactions in the toroidal metamolecule can be qualitatively represented by a theoretical model based on an electric point dipole arrangement. Both a finite-size rod model and the point dipole approximation demonstrate how the toroidal dipole moment is subradiant and difficult to excite by incident light. By means of breaking the geometric symmetry of the metamolecule, the toroidal mode can be excited by linearly polarized light and appears as a Fano resonance dip in the forward scattered light. We provide simple optimization protocols for maximizing the toroidal dipole mode excitation. This opens up possibilities for simplified control and driving of metamaterial arrays consisting of toroidal dipole unit-cell resonators.

to appear in PRB

References in corpus (5)

• Towards a microscopic theory of toroidal moments in bulk periodic crystals
• Toroidal order in metals without local inversion symmetry
• Toroidal dipole response in a multifold double-ring metamaterial
• Theoretical formalism for collective electromagnetic response of discrete metamaterial systems
• Resonance linewidth and inhomogeneous broadening in a metamaterial array

Cited by in corpus (12)

• Photonic toroidal vortex
• Many-body subradiant excitations in metamaterial arrays: Experiment and theory
• Toroidal eigenmodes in all-dielectric metamolecules
• Symmetry analysis of trimer-based all-dielectric metasurfaces with toroidal dipole modes
• Tuning toroidal dipole resonances in dielectric metamolecules by an additional electric dipolar response
• Strong radiative interactions and subradiance in disordered metamaterials
• Radiative toroidal dipole and anapole excitations in collectively responding arrays of atoms
• Transition between radial and toroidal orders in a trimer-based magnetic metasurface
• Point dipole and quadrupole scattering approximation to collectively responding resonator systems
• Cooperative field localization and excitation eigenmodes in disordered metamaterials
• Point-dipole approximation for small systems of strongly coupled radiating nanorods
• Anapole mode excitation in novel perforated all-dielectric metamaterials