Abstract
In this work we study the interaction of visible light with plasmonic nanodimers that, under particular illumination conditions, do not exhibit any electric dipole excitations. It has previously been found out that the dipole suppression phenomenon disappears when the illumination direction is reversed. As a consequence, a homogeneous nanomaterial consisting of such nanodimers can be expected to be spatially dispersive, such that the conventional electric polarization vanishes for certain directions of light propagation. In order to reveal the complete picture of the light-nanodimer interaction, we analyze the multipole excitations in a dimer at various illumination angles. In particular, we introduce an analytical model for the multipole polarizability tensors of the dimer that, in contrast to conventional polarizability tensors, depend on the light propagation direction. The model is verified by rigorous numerical calculations. It can be used to gain insight into the properties of optical nanomaterials, such as metamaterials, in which higher-order multipoles can be efficiently excited.
Highlights
The interaction of light with subwavelength-size particles is usually accurately described in terms of electric dipole excitations
In custom-designed optical nanomaterials the unit cell response can be tuned in such a way that other multipoles are excited as well [1], which leads to various interesting optical phenomena [2] and extraordinary optical effects [3]
In order to treat the nanomaterial as a homogeneous one, the dimensions of the unit cell must be much smaller than the illumination wavelength [5, 6]
Summary
In this work we study the interaction of visible light with plasmonic nanodimers that, under particular illumination conditions, do not exhibit any electric dipole excitations. A homogeneous nanomaterial consisting of such nanodimers can be expected to be spatially dispersive, such that the conventional electric polarization vanishes for certain directions of light propagation. In order to reveal the complete picture of the light-nanodimer interaction, we analyze the multipole excitations in a dimer at various illumination angles. We introduce an analytical model for the multipole polarizability tensors of the dimer that, in contrast to conventional polarizability tensors, depend on the light propagation direction. It can be used to gain insight into the properties of optical nanomaterials, such as metamaterials, in which higher-order multipoles can be efficiently excited.
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