Radial Anisotropy in Spheroidal Scatterers

Rimpiläinen, Tommi; Wallén, Henrik; Sihvola, Ari

doi:10.1109/tap.2015.2422835

Cited by 9 publications

(12 citation statements)

References 17 publications

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“…When we studied the way that the polarizability of an ellipse depends on the two material parameters, we found that combinations of parameters exist that make the inclusion lose its perturbation field. This and existing research 8,9,21,22 on similar inclusions made us expect a potential cloaking property of the ellipse. When we investigated the matter, we found that it is indeed possible to have the inclusion's perturbation field vanish, so that the internal field near the focal range vanishes concurrently.…”

Section: Discussionsupporting

confidence: 57%

“…In Sec. IV, we concluded that the polarizability of a radially anisotropic needle coincides with that of a homogeneous needle, according to (21), so that the homogeneous permittivity depends on the orientation of the excitation field. We also concluded that when the inclusion becomes circular, the polarizability in (22) coincides with that of a homogeneous circle with the homogeneous permittivity ( n t ) 1=2 .…”

Section: Cloaks and Concentratorsmentioning

confidence: 82%

“…The contrasting combination n < t produces inclusions that have been referred to as bulbic and that are known to enable cloaking. 21 This suggests a potential cloaking and concentration properties also for the radially anisotropic ellipse. The bulbic ellipse does, in fact, turn out to facilitate cloaking.…”

Section: Cloaks and Concentratorsmentioning

confidence: 92%

“…Existing research on radially anisotropic inclusions has shown that many canonical inclusions can serve as cloaks when the material parameters are adjusted suitably. 8,9,21,22 They are also known to exhibit field concentration. One of these field concentrating and cloaking canonical inclusions is the radially anisotropic circle, 8 which is a special case of the subject matter of the present study.…”

Section: Cloaks and Concentratorsmentioning

confidence: 99%

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Polarizability of radially anisotropic elliptic inclusion

Rimpiläinen

Wallén

Sihvola

2016

Journal of Applied Physics

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This article discusses a two-dimensional electrostatic scattering problem where an elliptic inclusion is suspended in a homogeneous background and impinged by an electric field which is uniform and static. The novelty of the discussion stems from the inclusion's material parameters. The material of the inclusion is assumed to be axially anisotropic, so that the axis of anisotropy aligns itself with the radial unit vector of the elliptic coordinate system. Similar varieties of anisotropy have been formerly referred to as radial anisotropy, and the same term is employed herein. The radially anisotropic elliptic inclusions are studied with an analytic method. The validation is likewise analytic. The validation method compares the new results with the results for radially anisotropic circles and homogeneous two-dimensional needles. The elliptic inclusion is found to facilitate both cloaking and field concentration. V C 2016 AIP Publishing LLC. [http://dx.

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Section: Discussionsupporting

confidence: 57%

Section: Cloaks and Concentratorsmentioning

confidence: 82%

Section: Cloaks and Concentratorsmentioning

confidence: 92%

Section: Cloaks and Concentratorsmentioning

confidence: 99%

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Polarizability of radially anisotropic elliptic inclusion

Rimpiläinen

Wallén

Sihvola

2016

Journal of Applied Physics

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“…The other branch of singularity appears l Radial anisotropy has been generalized to ellipsoidal inclusions. 44 There the "radial" direction has to be understood in the sense of the corresponding dimension in the ellipsoidal coordinate system. in the indefinite quadrant ε r > 0, ε t < 0.…”

Section: Radially Anisotropic Spherementioning

confidence: 99%

Electromagnetic Metamaterials: Homogenization and Effective Properties of Mixtures

Sihvola¹

2017

World Scientific Handbook of Metamaterials and Plasmonics

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This chapter presents homogenization principles for metamaterials and dielectric mixtures. The focus is on the principles with which homogenization brings forth emergence: such qualitatively new properties in the effective characterization that are not present in the constituent components that make the medium. The classical Maxwell Garnett mixing result is paralleled with the deterministic scattering problem of a composite sphere, and the resulting equivalence is exploited in translating known mixing results to scattering and absorption properties of simple scatterers and vice versa. Emphasis is given to the way mixing can lead to situations where the composite obeys an unexpected dispersion behavior that is not directly predictable from the knowledge of the dispersion of the component materials. The characteristics of the localized resonances and their dependence on geometrical and structural parameters in plasmonic nanoparticles are analyzed. Theoretical bounds for the effective permittivity of mixtures are discussed as well as situations in which these bounds can allow enhanced polarization and percolation effects.

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Implementing radial anisotropy with self-similar structures

2020

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Radial anisotropy in small objects has been linked to exotic optical properties. It can be implemented with a spherical inclusion that manifests self-similarity. We show that, when a self-similar, onion-like structure with alternating layers is homogenized by using an effective material approximation, the homogenized material becomes uniaxially anisotropic with the axis of anisotropy pointed radially outward from the center of the inclusion. This radial anisotropy becomes exact in the limit of a dense set of layers. The exact equivalence of the layered self-similar inclusion and the radially anisotropic inclusion manifests itself both in the effective permittivities of the two inclusions-when homogenized over the entire volumes-and in the internal potentials. Because the layered sphere and the radially anisotropic sphere are analogous, it is possible to study some of the interesting scattering features of radially anisotropic spheres in a realistic configuration. In particular, we show that the outcome of homogenizing the self-similar inclusion, and consequently the electric response, depends on what the core material at the center of the inclusion is and that a continuous transition between the two homogenization models is possible. The findings suggest intriguing applications in nanophotonics.

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Radial Anisotropy in Spheroidal Scatterers

Cited by 9 publications

References 17 publications

Polarizability of radially anisotropic elliptic inclusion

Polarizability of radially anisotropic elliptic inclusion

Electromagnetic Metamaterials: Homogenization and Effective Properties of Mixtures

Implementing radial anisotropy with self-similar structures

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