147 research outputs found
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Analytical model of resonant electromagnetic dipole-quadrupole coupling in nanoparticle arrays
An analytical model for investigations of multipole coupling effects in the finite and infinite nanoparticle arrays supporting electromagnetic resonances is presented and discussed. This model considers the contributions of both electric and magnetic modes excited in the nanoparticles, including electric and magnetic dipoles and electric and magnetic quadrupoles. The magnetic quadrupole propagator (Green's tensor) that describes the electromagnetic field generated by a point magnetic quadrupole source in all wave zones is derived. As an example, we apply the developed model to study infinite two-dimensional rectangular periodic arrays of spherical silicon nanoparticles supporting the dipole and quadrupole resonant responses. The correctness and accuracy of the analytical model are confirmed by the agreement of its results with the results of full-wave numerical simulations. Using the developed model, we show the electromagnetic coupling between electric dipole and magnetic quadrupole moments as well as between magnetic dipole and electric quadrupole moments even for the case of an infinite rectangular periodic array of spherical nanoparticles. The strong suppression of the dipole or quadrupole moment due to the coupling effects is demonstrated and discussed for spherical nanoparticle arrays. The analytical expressions for the reflection and transmission coefficients written with the effective dipole and quadrupole polarizabilities are derived for normal light incidences and zero-order diffraction. The derived expressions are applied to explain the lattice anapole (invisibility) states when the incident light is transmitted unperturbed through the silicon nanoparticle array. The important role of dipole and quadrupole excitations in scattering compensation resulting in the lattice anapole effect is explicitly demonstrated. The presented approach can be used for designing metasurfaces and further utilizing them in developing ultrathin functional optical elements.Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany's Excellence Strategy within the Cluster of Excellence PhoenixD [EXC 2122, 390833453]; Air Force Office of Scientific Research [FA9550-19-1-0032]This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
Irreducible Cartesian multipole decomposition of scattered light with explicit contribution of high order toroidal moments
Multipole decomposition is a powerful tool for analysis of electromagnetic systems. This work considers high order irreducible Cartesian multipole moments in approximation of electric 32-pole and magnetic 16-pole. The explicit contributions to scattering of high order toroidal moments up to toroidal electric octupole and toroidal magnetic quadrupole are demonstrated for a dielectric high refractive index scatterer. © 2020 IOP Publishing Ltd
Giant Photogalvanic Effect in Noncentrosymmetric Plasmonic Nanoparticles
Photoelectric properties of metamaterials containing non-centrosymmetric,
similarly oriented metallic nanoparticles embedded in a homogeneous
semiconductor matrix are theoretically studied. Due to the asymmetric shape of
the nanoparticle boundary, photoelectron emission acquires a preferred
direction, resulting in a photocurrent flow in that direction when
nanoparticles are uniformly illuminated by a homogeneous plane wave. This
effect is a direct analogy of the photogalvanic (or bulk photovoltaic) effect
known to exist in media with non-centrosymmetric crystal structure, such as
doped lithium niobate or bismuth ferrite, but is several orders of magnitude
stronger. Termed the giant plasmonic photogalvanic effect, the reported
phenomenon is valuable for characterizing photoemission and photoconductive
properties of plasmonic nanostructures, and can find many uses for
photodetection and photovoltaic applications.Comment: 8 pages, 4 figure
Asymmetrie and symmetric local surface-plasmonpolariton excitation on chains of nanoparticles
We theoretically study the features of the surface-plasmon-polariton (SPP) excitation on single or chains of spherical metal nanoparticles located near a metal surface with an inclined incident light beam. It is found that by tuning the incident angle of an external light beam and the parameters of the surface nanoparticle structures one could obtain symmetric or asymmetric excitation of SPP beams propagating into certain directions. The reasons and conditions for this behavior and the efficiency of SPF excitation as a function of the incident angle are discussed. © 2009 Optical Society of America
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Transmission and reflection features of all-dielectrics metasurfaces with electric and magnetic resonances
The effective multipole decomposition approach is applied to study the optical features of the silicon metasurface in the near-infrared. The spectral regions of perfect transmission and reflection have been analyzed using the Cartesian multipole decomposition. It is shown that transmission peaks appear due to the mutual interaction of multipole moments up to the third order, while reflection peaks are due to the dominant contribution of one of the multipole moments. The results of this work can be broadly applied to design novel metasurfaces, sensors, and optical filters.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
Polarization Switching Between Electric and Magnetic Quasi-Trapped Modes in Bianisotropic All-Dielectric Metasurfaces
A general strategy for the realization of electric and magnetic quasi-trapped modes located at the same spectral position is presented. This strategy's application makes it possible to design metasurfaces allowing switching between the electric and magnetic quasi-trapped modes by changing the polarization of the incident light wave. The developed strategy is based on two stages: the application of the dipole approximation for determining the conditions required for the implementation of trapped modes at certain spectral positions and the creation of the energy channels for their excitation by introducing a weak bianisotropy in nanoparticles. Since excitation of trapped modes results in a concentration of electric and magnetic energies in the metasurface plane, the polarization switching provides possibilities to change and control the localization and distribution of optical energy at the sub-wavelength scale. A practical method for spectral tuning of quasi-trapped modes in metasurfaces composed of nanoparticles with a preselected shape is demonstrated. As an example, the optical properties of a metasurface composed of silicon triangular prisms are analyzed and discussed
Scattering of a surface plasmon polariton beam by chains of dipole nanoparticles
Scattering and splitting of surface plasmon polaritons (SPPs) by a chain of strongly interacting nanoparticles located near a metal surface are numerically studied. The applied numerical model is based on the Green's function formalism and point-dipole approximation for scattering by nanoparticles. Dependencies of the splitting efficiency on the inter-particle distance in the chain and on the angle of incidence of the SPP Gaussian beam are considered. It is found that the splitting efficiency depends on the inter-particle distances especially when the angle between the SPP beam and the chain is relatively small. The role of multiple scattering in the SPP splitting by the chains of nanoparticles is also discussed. © 2008 Springer-Verlag
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