Applicability of point dipoles approximation to all-dielectric metamaterials

All-dielectric metamaterials consisting of high-dielectric inclusions in a low-dielectric matrix are considered as a low-loss alternative to resonant metal-based metamaterials. In this contribution we investigate the applicability of the point electric and magnetic dipoles approximation to dielectric meta-atoms on the example of a dielectric ring metamaterial. Despite the large electrical size of high-dielectric meta-atoms, the dipole approximation allows for accurate prediction of the metamaterials properties for the rings with diameters up to ~0.8 of the lattice constant. The results provide important guidelines for design and optimization of all-dielectric metamaterials.Comment: 10 pages, 5 fugures, submitted to Physical Review

Homogenization of metasurfaces formed by random resonant particles in periodical lattices

In this paper we suggest a simple analytical method for description of electromagnetic properties of a geometrically regular two-dimensional subwavelength arrays (metasurfaces) formed by particles with randomly fluctuating polarizabilities. Such metasurfaces are of topical importance due to development of mass-scale bottom-up fabrication methods, for which fluctuations of the particles sizes, shapes, and/or composition are inevitable. Understanding and prediction of electromagnetic properties of such random metasurfaces is a challenge. We propose an analytical homogenization method applicable for normal wave incidence on particles arrays with dominating electric dipole responses and validate it with numerical point-dipole modeling using the supercell approach. We demonstrate that fluctuations of particles polarizabilities lead to increased diffuse scattering despite the subwavelength lattice constant of the array. The proposed method can be readily extended to oblique incidence and particles with both electric and magnetic dipole resonances.Comment: 10 pages, 5 figure

Bloch-mode analysis for retrieving effective parameters of metamaterials

We introduce a new approach for retrieving effective parameters of metamaterials based on the Bloch-mode analysis of quasi-periodic composite structures. We demonstrate that, in the case of single-mode propagation, a complex effective refractive index can be assigned to the structure, being restored by our method with a high accuracy. We employ both surface and volume averaging of the electromagnetic fields of the dominating (fundamental) Bloch modes to determine the Bloch and wave impedances, respectively. We discuss how this method works for several characteristic examples, and demonstrate that this approach can be useful for retrieval of both material and wave effective parameters of a broad range of metamaterials.Comment: 12 pages, 10 figure

Nested structures approach in designing an isotropic negative-index material for infrared

We propose a new generic approach for designing isotropic metamaterial with nested cubic structures. As an example, a three-dimensional isotropic unit cell design "Split Cube in Cage" (SCiC) is shown to exhibit an effective negative refractive index on infrared wavelengths. We report on the refractive index reaching -2.3 and the figure of merit as high as 2.7. The structure exhibits potential for application as a building block of isotropic negative-index materials

High symmetry versus optical isotropy of a negative-index metamaterial

Optically isotropic metamaterials (MMs) are required for the implementation of subwavelength imaging systems. At first glance one would expect that their design should be based on unit cells exhibiting a cubic symmetry being the highest crystal symmetry. It is anticipated that this is a sufficient condition since it is usually assumed that light does not resolve the spatial details of MM but experiences the properties of an effective medium, which is then optically isotropic. In this work we challenge this assumption by analyzing the isofrequency surfaces of the dispersion relation of the split-cube in carcass (SCiC) negative index MM. We show that this MM is basically optically isotropic, but not in the spectral domain where it exhibits negative refraction. The primary goal of this contribution is to introduce a tool that allows to probe a MM against optical isotropy

The split cube in a cage: Bulk negative-index material for infrared applications

Abstract We propose the split cube in a cage (SCiC) design for application in producing a bulk metamaterial. Applying realistic material data for thin silver films, we observe an immediate convergence of the effective parameters obtained with a number of layers towards the bulk properties. Results are obtained by two different numerical techniques: the Fourier modal method and the finite integrals method, thus ensuring their validity. The SCiC exhibits a refractive index of −0.6 for frequencies close to the telecommunication bands. The fast convergence of effective parameters allows consideration of the SCiC as a bulk (effectively homogeneous) negative-index metamaterial even for a single layer. The bulk-like nature together with the cubic symmetry of the unit cell make the SCiC a promising candidate for potential applications at telecommunication frequencies