Dynamic Anapole in Metasurfaces made of Sculptured Cylinders
arXiv:1905.02195 · doi:10.1103/PhysRevB.100.085431
Abstract
We present all-dielectric polaritonic metasurfaces consisting of properly sculptured cylinders to sustain the dynamic anapole, i.e. a non-radiating alternating current distribution. One way for the anapole to emerge, is by combining modes based on the first and the fourth Mie resonance of a cylinder made of high permittivity LiTaO for operation in the low THz. The circular cross-section of each cylinder varies periodically along its length in a binary way, from small to large, while its overall circular symmetry has to be broken in order to remove parasitic magnetic modes. Small cross-sections are the main source of the \textit{electric dipole} Mie mode, while large cross-sections sustain the fourth, \textit{mixed toroidal dipole} Mie mode. With proper adjustment, the generated electric and toroidal moments interfere destructively producing a non-radiating source, the dynamic anapole, the existence of which is attested by a sharp dip in the reflection from the metasurface, due exclusively to electric and toroidal dipoles. Moreover, we show that, by breaking the circular symmetry of each cylinder, a substantial toroidal dipole emerges from the \textit{magnetic quadrupole} Mie mode, which in combination with the electric dipole also produces the dynamic anapole. The sensitivity of the anapole states to the material dissipation losses is examined leading to the conclusion that the proposed metasurfaces offer a scheme for realistically implementing the anapole.
arXiv comment24 pages, 8 figures
References in corpus (13)
- Nonradiating Photonics with Resonant Dielectric Nanostructures
- Non-Trivial Non-Radiating Excitation as a Mechanism of Resonant Transparency in Toroidal Metamaterials
- Optical anapoles in nanophotonics and meta-optics
- Dielectric Metamaterials with Toroidal Dipolar Response
- Anapole-Assisted Strong Field Enhancement in Individual All-Dielectric Nanostructures
- Excitation of radiationless anapole mode of isotropic dielectric nanoparticles with tightly focused radially polarized beam
- Optical toroidal dipolar response by an asymmetric double-bar metamaterial
- Direct amplitude-phase near-field observation of higher-order anapole states
- Invisible nanowires with interfering electric and toroidal dipoles
- Toroidal eigenmodes in all-dielectric metamolecules
- Non-radiating sources, dynamic anapole and Aharonov-Bohm effect
- Scattering invisibility with free-space field enhancement of all-dielectric nanoparticles
- Tuning toroidal dipole resonances in dielectric metamolecules by an additional electric dipolar response