Depolarization regions of nonzero volume in bianisotropic homogenized composites

In conventional approaches to the homogenization of random particulate composites, the component phase particles are often treated mathematically as vanishingly small, point-like entities. The electromagnetic responses of these component phase particles are provided by depolarization dyadics which derive from the singularity of the corresponding dyadic Green functions. Through neglecting the spatial extent of the depolarization region, important information may be lost, particularly relating to coherent scattering losses. We present an extension to the strong-property-fluctuation theory in which depolarization regions of nonzero volume and ellipsoidal geometry are accommodated. Therein, the size, shape and spatial distribution of the component phase particles are taken into account. The analysis is developed within the most general linear setting of bianisotropic homogenized composite mediums (HCMs). Numerical results are presented for a representative example of a bianisotropic HCM, namely a Faraday chiral medium. These studies reveal that estimates of the HCM constitutive parameters in relation to volume fraction, particle eccentricity, particle orientation and correlation length are all significantly influenced by the size of the component phase particles.     

Inclusion of a nonzero volume fraction of the new phase in the kinetics of crystallization of melts

The growth rate of nuclei is calculated in self-consistent mean field approximation with allowance for the screening of a selected nucleus from heat fluxes, and an expression is obtained for the screening length of the heat flux. It is shown that the growth rate of a nucleus depends on the degree of crystallization of the melt. The influence on the crystallization process of collisions of the particles as they coalesce into a polycrystalline solid is investigated. A refinement of the size distribution function in the thermal Ostwald ripening stage is obtained. Zh. Tekh. Fiz. 69, 53–58 (July 1999)     

Terahertz wave polarization rotation in bianisotropic metamaterials

Utilizing a polarization sensitive terahertz detection method where the detector is rotated by either 0° or 90° to measure the electric field E_{p, s} (t) of each polarization component, we have characterized the properties of split ring resonators. The strong polarization dependence of the bianisotropic-circular-current-driven and linear-polarization-induced resonances is in excellent agreement with the simulation when the p-polarized terahertz transmission is measured. However, these electromagnetic responses vanish when the s-polarized terahertz transmission is measured. There is only a transmission minimum at 1.64 THz and the terahertz polarization rotation angle of about 90° is observed. The polarized terahertz transmission amplitudes and spectra detected at orthogonal orientations show that these behaviours are probably attributed to the birefringent effect of the sample.     

Effective constitutive parameters of plane-stratified bianisotropic structures

The method of 4×4 matrices is used to determine the effective constitutive parameters of a plane-stratified bianisotropic structure without any restrictions on the ratio of the period of the structure to the wavelength. The effective dielectric, magnetic, and magnetoelectric constants of isotropic two-layer and anisotropic helicoidal structures are found in the resonant case.     

Scattering response of an electrically small bianisotropic particle

Scattering response of an electrically small bianisotropic particle suspended in free space is presented. Formulation of this problem is based on the assumption that the electrical small bianisotropic particle can be modelled as both an equivalent electric and a magnetic dipole moments. It is found that cross-polarization and/or co-polarization phenomena may occur for certain constitutive relations, separatively.     

Transmission of an electromagnetic wave through a bianisotropic metafilm

Transmittance and reflectance are analytically calculated for the light of arbitrary polarization incident on the two-dimensional lattice (metafilm) composed of bianisotropic particles with the known polarizability matrix. The results of calculating the coefficients for metafilms composed of U-shaped particles are presented.     

Comparison of two methods for oblique propagation in helicoidal bianisotropic mediums

Two methods for oblique propagation in two dielectric examples of helicoidal bianisotropic mediums – chiral sculptured thin films and chiral smectic liquid crystals – are compared: (i) the series solution method, and (ii) the piecewise homogeneity approximation method. Both have to be numerically implemented, although only the former relies on an exact analytic solution of the frequency-domain Maxwell postulates. Convergence in the series solution method is investigated via calculations for a variety of planewave-illumination parameters and constitutive properties. Likewise, the maximum slice thickness for convergent results from the piecewise homogeneity approximation method is also studied. The computational efficiencies of both methods are compared.     

Reflection and transmission of plane electromagnetic waves in uniaxial bianisotropic materials

Electromagnetic waves in the most general linear reciprocal uniaxial media are considered. The theory is appropriate for novel reciprocal microwave materials which have properties of chiral composites and omega structures (or both) and can be modeled by uniaxial bianisotropic constitutive relations. Field coupling terms in the media equations are assumed to be the most general uniaxial dyadics with symmetric and antisymmetric components. Plane eigenwaves in unbounded media are studied and the theory of reflection and transmission in plane layers is constructed.     

Depolarization in a photosensitive relaxor ferroelectric

This paper reports a study of depolarization of a photosensitive relaxor ferroelectric Sr_0.61Ba_0.39Nb₂O₆ with 0.44 at. % La and 0.023 at. % Ce impurities at room temperature and under illumination of up to 0.22 mW/cm² in the absorption band of the crystal. The best fit to the experimental data was found with a function containing two time-dependent power-law terms. The approximation reflects two simultaneously operating polarization decay mechanisms, more specifically, polydomainization in the depolarizing field of a bounded crystal and screening of this field by photoinduced carriers. Exact double-humped distribution functions of nonexponential relaxation centers in the crystal have been derived from the relaxation times. Illumination shifts the distribution functions toward longer relaxation times.     

Decay of correlations in Fermi systems at nonzero temperature

The locality of correlation functions is considered for Fermi systems at nonzero temperature. We show that for all short-range, lattice Hamiltonians, the correlation function of any two fermionic operators decays exponentially with a correlation length which is of order the inverse temperature for small temperature. We discuss applications to numerical simulation of quantum systems at nonzero temperature.     

Bunching of particles with nonzero longitudinal emittance

The dynamics of the bunching of particles with nonzero longitudinal emittance is studied in plane geometry. A self-consistent solution to the model time-dependent kinetic equation is obtained for a collisionless system of particles. The solution is shown to be nonunique. Two acceleration modes resulting in the creation of a virtual cathode and, therefore, in the bunching of particles are basically possible.     

Scattering response of a bianisotropic cylinder with electrically small cross-section

EM scattering response of an infinitely long bianisotropic cylinder with electrically small cross-section suspended in free space is presented. Formulation of this problem is based on the coupled integral equation method with the long wavelength approximation. Reduced expressions for the scattering of plane waves, both E-wave and H-wave types, are obtained. It is revealed that for certain polarization matrices determined by the constitutive parameters of the scatterer, cross-polarization and/or co-polarization phenomena may occur, respectively.     

Perturbation of a resonant cavity by a small bianisotropic sphere

Perturbation of a resonant cavity by the introduction of a small bianisotropic sphere in its interior is analyzed. It is shown that the resonance frequency can be altered merely by rotating the bianisotropic sphere at a fixed location.     

Depolarization of partially coherent light in liquid crystals

In the paper we present results of analysis of partially coherent light depolarization in two types of liquid crystals possessing linear birefringence controlled by temperature and external electric field changes. Some experimental results of degree of polarization measurements for different light sources as a superluminescent diode and a laser diode are also presented.