26 research outputs found
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
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