Elusive pure anapole excitation in homogenous spherical nanoparticles with radial anisotropy

Abstract

For homogenous isotropic dielectric nanospheres with incident plane waves, Cartesian electric and toroidal dipoles can be tunned to cancel each other in terms of far-field scattering, leading to the effective anopole excitation. At the same time however, other multipoles such as magnetic dipoles with comparable scattered power are simultanesouly excited, mixing with the anopole and leading to a non-negligible total scattering cross section. Here we show that for homogenous dielectric nanospheres, radial anisotropy can be employed to significantly suppress the other multipole excitation, which at the same time does not compromise the property of complete scattering cancallation between Cartesian electric and toroidal dipoles. This enables an elusive pure anopole excitation within radially anisotropic dielectric nanospheres, which may shed new light to many scattering related fundamental researches and applications.

Invited submission with four figures and ten pages. Comments welcomed

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• Nonradiating anapole states in nanophotonics: from fundamentals to applications
• Multipolar interference effects in nanophotonics
• Hybrid Nanophotonics
• Theory, observation and ultrafast response of novel hybrid anapole states
• Nontrivial Pure Zero-Scattering Regime Delivered by a Hybrid Anapole State
• Nonlinear Metasurfaces: A Paradigm Shift in Nonlinear Optics
• Anapole mode excitation in novel perforated all-dielectric metamaterials