Inhomogeneous Chiral Media Research Articles

Investigation of reflections of terahertz waves from an inhomogeneous planar layer of a chiral metamaterial with allowance for frequency dispersion

The main purpose of this work is to develop a method for calculating the reflections of linearly polarized waves from an inhomogeneous planar layer of a chiral metamaterial. A mathematical model of a homogeneous inhomogeneous chiral medium is considered taking into account the frequency dispersion of material parameters. The moduli of the reflection coefficients of the main and cross-polarized field components from an inhomogeneous layer with parabolic and linear profiles of changes in the resonant frequency of a chiral metamaterial are calculated. It is shown that inhomogeneous planar structures of chiral metamaterials can significantly reduce the level of reflection of cross-polarized waves in the optical and terahertz ranges.

Surface waves in an open circular waveguide filled with inhomogeneous chiral media

Propagation of surface waves in a radially inhomogeneous chiral waveguide is considered. The setting is reduced to a boundary eigenvalue problem for the longitudinal components of the electromagnetic field in Sobolev spaces. To find the solution, variational formulation is used. The variational problem is reduced to the analysis of an operator-valued function. Discreteness of the spectrum is proved and distribution of the characteristic numbers of the operator-valued function on the complex plane is determined. The results of numerical modeling of the spectrum of propagating surface waves in an open chiral waveguide are presented.

Perfect cloaking by shell with radially inhomogeneous chiral medium

This paper investigates the electromagnetic cloaking features of a spherical dielectric nanoparticle enclosed by a uniform shell of the inhomogeneous chiral medium. The cloaking characteristics were analyzed in terms of the effective permittivity of the nanoparticle. In this regard, effective permittivity was analyzed as a function of the chirality parameter, radial permittivity, and inhomogeneity parameter of the medium filling the shell. The results show the unit effective permittivity of the proposed core–shell nanoparticle attribute to the cloaking property.

Matrix solution 4x4 by the Wentzel-Kramers-Brillouin method for electromagnetic waves reflected on the boundary of inhomogeneous chiral layer

The propagation of a plane electromagnetic wave in a plane inhomogeneous chiral medium with oblique incidence is considered. The chirality parameter varies with the distance from the boundary. The problem reduces to solving a system of the ordinary differential equations (ODE) with variable coefficients 4x4. The solution was obtained by the Wentzel-Kramers-Brillouin method in the matrix form. We found a fundamental solution matrix and a Cauchy matrix for a chiral inhomogeneous medium with continuously varying properties along one of the coordinates. The dependence of the absolute values of the matrix coefficients of reflection and cross-polarization components on the reflection from the profile of the chirality parameter and the angle of incidence is shown.

Coriolis effect and spin Hall effect of light in an inhomogeneous chiral medium.

We theoretically investigate the spin Hall effect of spinning light in an inhomogeneous chiral medium. The Hamiltonian equations of the photon are analytically obtained within eikonal approximation in the noninertial orthogonal frame. Besides the usual spin curvature coupling, the chiral parameter enters the Hamiltonian as a spin-torsion-like interaction. We reveal that both terms have parallel geometric origins as the Coriolis terms of Maxwell's equations in nontrivial frames.

Resonant absorption and amplification of circularly-polarized waves in inhomogeneous chiral media.

It has been found that in the media where the dielectric permittivity ε or the magnetic permeability μ is near zero and in transition metamaterials where ε or μ changes from positive to negative values, there occur a strong absorption or amplification of the electromagnetic wave energy in the presence of an infinitesimally small damping or gain and a strong enhancement of the electromagnetic fields. We attribute these phenomena to the mode conversion of transverse electromagnetic waves into longitudinal plasma oscillations and its inverse process. In this paper, we study analogous phenomena occurring in chiral media theoretically using the invariant imbedding method. In uniform isotropic chiral media, right-circularly-polarized and left-circularly-polarized waves are the eigen-modes of propagation with different effective refractive indices n(+) and n(-), whereas in the chiral media with a nonuniform impedance variation, they are no longer the eigenmodes and are coupled to each other. We find that both in uniform chiral slabs where either n(+) or n(-) is near zero and in chiral transition metamaterials where n(+) or n(-) changes from positive to negative values, a strong absorption or amplification of circularly-polarized waves occurs in the presence of an infinitesimally small damping or gain. We present detailed calculations of the mode conversion coefficient, which measures the fraction of the electromagnetic wave energy absorbed into the medium, for various configurations of ε and μ with an emphasis on the influence of a nonuniform impedance. We propose possible applications of these phenomena to linear and nonlinear optical devices that react selectively to the helicity of the circular polarization.

Analysis of Line Source Radiation Above Grounded Inhomogeneous Chiral Layer Using a Hybrid Method of Fourier Transform and Taylor's Series Expansion

An analytical approach is introduced to analyze scattering and wave propagation in the problem involving a line source near an inhomogeneous chiral slab based on combination of Fourier transform and Taylor's series expansion. In this method, Taylor's series expansion is used for all electromagnetic parameters and Fourier transformed electric and magnetic fields of the inhomogeneous chiral medium. The unknown coefficients of the electric and magnetic fields in the Fourier domain are found by solving a system of linear coupled equations. For verification purpose, some special examples are considered, and the obtained results from this method are compared to the available exact solutions.

The ray method in an inhomogeneous chiral medium and admixed components of an electromagnetic field

In this paper, a complete asymptotic expansion of a high-frequency electromagnetic field in chiral media is constructed. Recurrence formulas for the coefficients of the expansion are found. Polarizations of electromagnetic waves are found and explained in the zero approximation. Bibliography: 5 titles.

Floquet-Bloch waves in periodic chiral media.

The Floquet-Bloch waves in periodically inhomogeneous chiral media are considered. The wave vectors are assumed to be arbitrarily oriented with respect to the grating vector. We have formulated general equations of the dynamical diffraction by such a medium and have analyzed them in the two-wave approximation under different conditions. It is shown that the band structure of the eigenmode spectrum can be qualitatively modified under the effect of chirality. At a sufficiently large chiral admittance, the band gap that is forbidden for a given circularly polarized wave is split into two---central band gap and chiral satellite---which are separated by an interval of transparency. The bandwidth of the satellite is strongly dependent on the propagation angle and approaches zero as the wave vectors tend to be collinear with the grating vector. A change from the conventional Bragg diffraction band structure to the complex-split one is through the range where points of [ital J] multiplicity and anomalous dispersion are characteristic of the spectrum. The boundary-value problem under diffraction by a periodic chiral layer is also analyzed. A unified expression for the reflection coefficient of the layer suitable over the entire region of the two-wave diffraction was obtained in the case of themore » complex-split spectrum. It is shown that the presence of satellites in the spectrum results in the appearance of additional reflection band gaps spaced both above and below in frequency relative to the central band gap. Unlike the latter, the side band gaps each are opaque for a given circularly polarized component of an incident field whereas the oppositely polarized component passes through the layer without Bragg reflection.« less

On Electromagnetic Fields in a Periodically Inhomogeneous Chiral Medium

Abstract Electromagnetic fields in a periodically inhomogeneous chiral medium are examined. The constitutive properties of the chiral medium vary along the z axis, and reduced fields with prescribed x-variations are used. Coupled first-order differential equations are derived to describe the reduced fields. Two special cases -(i) piecewise constant inhomogeneity, and (ii) constant impedance inhomogeneity, - are discussed in detail, and solution procedures are provided

Polarization correction of luneburg lens with chiral medium

AbstractThe geometrical optics method for the wave propagation in inhomogeneous chiral media, introduced recently, is here applied to the Luneburg lens antenna. For sufficiently small values of the chirality parameter, the geometrical optics rays can be calculated as for the achiral medium and the main effect of the chirality is rotation of polarization along the ray. This effect can be exploited to correct the polarization in the aperture of a lens antenna. In this paper the cross polarization of the Luneburg lens is eliminated through use of an inhomogeneous chirality distribution.

Propagation along the direction of inhomogeneity in an inhomogeneous chiral medium

Wave propagation in unidirectionally inhomogeneous chiral media is examined, i.e. the constitutive properties of the chiral media vary along the z axis; it is also assumed that the electromagnetic field is a function of the z coordinate alone. It is shown that the electromagnetic field, in the present arrangement, can be decomposed into two mutually-independent circularly-polarized states. Coupled first-order differential equations are derived to describe the fields, and various solution procedures discussed. Extension is made to the case when the medium inhomogeneity is periodic, for which case a perturbational solution is explicitly given.