Effective Electromagnetic Response Research Articles

Broadband Applications of a Tunable Nano-Rod Metaferrite

The rigorous analytical model of broadband effective electromagnetic response of the two-component metaferrite is presented in this study in the range up to THz frequencies. The metaferrite is a square array of ferric or ferromagnetic infinitely long cylinders of circular cross section symmetrically imbedded into homogenous isotropic dielectric host medium. It is assumed that the cylinders are fully or partially magnetized by a dc biasing magnetic field directed along the cylinder axes. Expressions of the complex effective permeability and permittivity tensors are obtained in the study. Expressions of the complex effective relative permeability and permittivity transverse to the direction of magnetization are derived and analyzed as functions of the frequency of incident electromagnetic wave and constitutive parameters of the metaferrite.It is shown that tuning a dc biasing magnetic field enables to effectively change the transmittivity and reflectivity of the metaferrites in the considered frequency range. We were also able to show that a layer of the metaferrite can be used for exciting surface plasmons at GHz frequencies. Finally, we have discussed the principal possibility of usage of the considered metaferrite for fabricating the substrates of miniaturized patch antennas with improved performance.

Advanced microwave effective medium theory for two-component nonmagnetic metamaterials: fundamentals and antenna substrate application

A modification of effective medium theory for two-component nonmagnetic metal---dielectric metamaterials is developed for use in the microwave frequency range. The metamaterial is represented as an unbounded isotropic dielectric host material with periodically embedded nonmagnetic metallic inclusions of cylindrical or spherical shape. The effective electromagnetic response of the metamaterial is represented by the tensor of the effective relative permittivity and tensor of the effective relative permeability. The losses of the metamaterial are also evaluated in this study. A physical interpretation for the nature of the effective properties of such metamaterials is given. Analytical models of the proposed effective medium theory are benchmarked against numerical simulations using commercial electromagnetic software. Two compact microwave rectangular dual-band patch antennas on such metamaterial substrates are designed in this study.

Nonresonance effective electromagnetic response of sandwich metamaterial with ferrite inclusions

Purpose – The purpose of this paper is to obtain the long‐wave approximations for the effective electromagnetic response of two‐dimensional sandwich composite structure, as infinite chain of infinitely long metal cylinders symmetrically immersed in an infinite metamaterial slab are obtained. The slab is an infinite magneto‐dielectric matrix with periodically imbedded infinitely long metal cylinders whose diameter is smaller than those of the chain cylinders. The case of ferrite‐like metallic saturated inclusions is considered in the study.Design/methodology/approach – The result is presented as a generalized expression of the electromagnetic response of the infinite periodic chain of infinitely long metallic cylinders immersed into the flat magneto‐dielectric host medium. Those expressions were obtained utilizing S‐ and T‐matrices approaches.Findings – A good coincidence between the results of analytical modeling and numerical simulations was found.Research limitations/implications – Low values of the met...

On the definition of the Poynting vector: A non-local derivation

We review a formalism developed previously to deal with the non-local (spatially dispersive) effective electromagnetic response of colloidal systems. We use this formalism to find, in the long wavelength limit, a general expression for the local energy conservation theorem in terms of parameters associated to the non-local response of the system. We find an explicit expression for the Poynting vector in terms of these non-local parameters and show that there are several ways to write it in terms of the electric permittivity and the magnetic permeability. The significance of this problem in the treatment of refraction is also discussed.

Scattering loss in electro-optic particulate composite materials

The effective permittivity dyadic of a composite material containing particulate constituent materials with one constituent having the ability to display the Pockels effect is computed, using an extended version of the strong-permittivity-fluctuation theory which takes account of both the distributional statistics of the constituent particles and their sizes. Scattering loss, thereby incorporated in the effective electromagnetic response of the homogenized composite material, is significantly affected by the application of a low-frequency (dc) electric field.

Impact of inherent periodic structure on effective medium description of left-handed and related metamaterials

We study the frequency dependence of the effective electromagnetic parameters of left-handed and related meta-materials of the split ring resonator and wire type. We show that the reduced translational symmetry (periodic structure) inherent to these meta-materials influences their effective electromagnetic response. To anticipate this periodicity, we formulate a periodic effective medium model which enables us to distinguish the resonant behavior of electromagnetic parameters from effects of the periodicity of the structure. We use this model for the analysis of numerical data for the transmission and reflection of periodic arrays of split ring resonators, thin metallic wires, cut wires as well as the left-handed structures. The present method enables us to identify the origin of the previously observed resonance/anti-resonance coupling as well as the occurrence of negative imaginary parts in the effective permittivities and permeabilities of those materials. Our analysis shows that the periodicity of the structure can be neglected only for the wavelength of the electromagnetic wave larger than 30 space periods of the investigated structure.

Non-local Effective Medium for the Electromagnetic Response of Colloidal Systems: a T-matrix Approach

We show the nonlocal nature of the effective electromagnetic response of a colloidal system with large particles and derive closed expressions for both, the effective nonlocal electric permittivity and the magnetic susceptibility.

Effective medium theory of the microwave and the infrared properties of composites with carbon nanotube inclusions

Carbon nanotubes (CNs) are electrically small particles at infrared and microwave frequencies. The Mossotti–Clausius formalism for estimating the effective permittivity dyadic of a dilute composite containing CN inclusions is described, and simplifications for certain orientational statistics are discussed. The polarizability dyadic of an electrically small CN is estimated from that of an infinitely long CN of the same cross-sectional diameter. A collection of randomly dispersed, aligned, nonchiral, electrically small CNs is shown to be transparent in the axial direction, but it can be either opaque or transparent in the transverse plane. Its effective electromagnetic response properties can be manipulated by a biasing magnetic field.

Effective electromagnetic response in superconductor-normal metal composites

The effective far-infrared response of a superconductor-normal metal (S/N) composite is studied within the effective medium approximation. In particular, the effects of a finite relaxation time τ s, which represents a generalization of the τ s=0 Mattis-Bardeen form, are studied. The effects of varying τ s and the concentration of the superconducting component on the effective conductivity and effective reflectivity of the composite are investigated. Possible applications of our calculations to the high temperature superconductors are discussed.