Scattering of electromagnetic waves by a layer of air plasma surrounding a conducting cylinder

In this paper, the total scattering and back-scattering cross-sections (respectively represented by and _b) of an air plasma layer surrounding a conducting cylinder are studied. The plasma layer can be turned ON and OFF to allow for a comparison between the scattering cross-section of the bare cylinder and the plasma covered cylinder. The plasma layer is generated at atmospheric pressure, which results in a very highly collisional case. The scattered fields are calculated using a cylindrical expansion, with coefficients satisfying the appropriate boundary conditions, and which are a function of the refractive index of the air plasma. The results of our study are presented as plots of the total scattering cross-section, , and back-scattering cross-section, _b, versus frequency. The scattering cross-section gives an average characteristic of the scattering process from obstacles. Once the scattering cross-section is known, the actual scattered energy per unit length per second can be calculated by multiplying by the incident energy per unit area per second.     

Dispersion and instability of electromagnetic waves in layered periodic semiconductor structures

The effect of carrier drift on the dispersive properties and instability of electromagnetic waves and plasma polaritons in infinite layered periodic semiconductors are considered. It is assumed that in similar semiconductor layers, carriers drift parallel to the interfaces. Drift waves are shown to have a specific band structure of the spectrum. The dispersive properties of collective plasma polaritons under drift are considered, the instability of the polaritons and drift waves is studied, and the instability increments are determined.     

Scattering of electron stream waves on metal-dielectric periodic structures

The results of the theoretical and experimental research of the surface waves scattering of an electron stream and a planar dielectric waveguide on metal-dielectric structures of the dielectric prism — band diffraction grating-type are presented. Within the approximation of the given current there has been carried out a numerical analysis of energy characteristics of diffraction-Cerenkov radiation for a wide interval of the main system parameters change. The results of numerical analysis are confirmed by the data of experimental simulation.     

Propagation of electromagnetic waves in a conducting magnetic medium

We study helicon-spin waves (hybrid polaritons) in a ferromagnetic conducting medium in a strong static magnetic field and determine their existence domains. It is shown that the spatial dispersion of the conductivity tensor gives rise to collisionless damping of these waves when they propagate obliquely to the magnetic field. In the absence of collisionless damping (for wave propagation along the magnetic field), the conditions of amplification of hybrid polaritons in a static electric field are determined. Institute of Radiophysics and Electronics, National Academy of Sciences of Ukraine, Kharkov, Ukraine. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol.43, No. 1, pp. 38–44, January 2000.     

Effect of anisotropy of a medium on the scattering of electromagnetic waves by a subsurface inclusion

We have constructed a physicomathematical model of scattering of electromagnetic waves by a homogeneous object immersed in a material halfspace, which allows for anisotropy of electromagnetic properties of the scatterer and surrounding medium. This model is motivated by the need for remote sensing, nondestructive testing, and microwave devices and is based on the numerical solution of a system of integral equations for the electric field components inside an inclusion using the method of moments. We present numerical examples that illustrate wave scattering by an inhomogeneity in sea ice and polymer composite. State University, Khar’kov, Ukraine. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 10, pp. 1249–1259, October, 1997.     

Dual electronic tunability of the dispersion characteristics of electromagnetic-spin waves in high-anisotropic layered multiferroic structures

Electric and magnetic tuning of phase, frequency, and delay time of electromagnetic-spin waves in thin-film layered multiferroic structure (metal-dielectric gap-ferroelectric material-hexaferrite-dielectric substrate) is numerically simulated. The results are used to demonstrate prospects for application of layered multiferroic hexaferrite-ferroelectric structures in the construction of basically new devices for generation and processing of microwave signals under dual (electric and magnetic) tuning of the working characteristics in the subterahertz frequency range.     

Additional electromagnetic waves in a uniaxial crystal with anisotropy fluctuations

It has been shown that the inclusion of orientational fluctuations of the axes of nonpolar axially symmetric molecules leads to a spatial dispersion of the permittivity of a uniaxial crystal. Expressions for the local field, polarization, and principal values of the permittivity tensor of the crystal have been derived. An estimate has been made of the wavelength above which the contribution to the spatial dispersion of orientational fluctuations of the molecular axes dominates. The phase velocities of the ordinary and extraordinary electromagnetic waves in a uniaxial crystal have been determined. It has been demonstrated that additional slow extraordinary electromagnetic waves can exist near the zeros of the principal values of the permittivity tensor of the crystal in particular ranges of angles between the wave vector and the optic axis of the crystal.     

Love waves in layered flexoelectric structures

Abstract

In this paper, the flexoelectric effect on Love waves propagating in a structure with a nanoscale piezoelectric guiding layer deposited on an isotropic elastic substrate is analytically investigated. Transcendental complex dispersion equations are obtained and solved numerically which are corresponding to the electrically open and short conditions at the free surface. A detailed discussion about the dispersion relations of the fundamental mode is subsequently presented. The results indicate that flexoelectricity has a substantial effect on Love wave propagation. The presence of flexoelectricity leads to a complex phase velocity with a negative/positive imaginary part, which means Love waves attenuate/grow over time. In addition, the phase velocity dispersion relations depend greatly on the thickness and flexoelectric coefficients of the guiding layer. The current work is the first attempt to explore the flexoelectric effect on the propagation characteristics of surface acoustic waves (SAWs). And the results would be beneficial to achieve a better performance of SAW devices.     

Natural electromagnetic waves in round inhomogeneous layered waveguides

A general theory of gyrotropic waveguide is considered. The theory allows the entire spectrum of natural electromagnetic waves and oscillations in regular waveguide structures discretely inhomogeneous in their cross sections to be obtained. A mathematical model is discussed that enables the propagation constants to be calculated for an arbitrary number of bigyrotropic layers of the structure based on an informal algorithmic formulation of the dispersion equation. Examples of numerical analysis of electrodynamic structures are given. They provide the basis for the development of gyromagnetic microwave devices and measuring cutoff converters intended for monitoring of the electrophysical characteristics of various materials and fluid media. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 15–19, September, 2006.     

Transition between layered and filamentary types of anisotropy in layered superconducting structures

A model of layered superconducting structure consisting of alternating anisotropic superconducting layers S₁ and S₂ with different transition temperatures is considered. It is shown that due to competition between two origins of anisotropy - effective-mass anisotropy of individual layers and proximity-induced anisotropy the effective anisotropy of the whole system signficiantly varies temperature. The components of the effective-mass tensor m_c (along the anisotropy axis) and m_a (perpendicular to the anisotropy axis) strongly depend upon temperature. This may lead to transition between layered (m_c > m_a) and quasi one-dimensional (m_c < m_a) types of anisotropy as well as to biaxial-type anisotropy which is also temperature dependent. The field distribution in a tilted vortex in a biaxial superconductor is calculated. The change in the properties of the vortex lattice with temperature in such systems is also investigated. The properties of YBa₂Cu₃O_x/PrBa₂Cu₃O_y multilayers are discussed in this connection.     

Propagation of electromagnetic waves in conducting graphene-like carbon nanoallotropes

Propagation of electromagnetic waves in graphene-like conducting carbon crystals with the (C)_4ν and (C)_6ν symmetries is studied. It is demonstrated that only TM waves can exist in such crystals. The comparative analysis of such waves in different structures is performed. It is shown that the structures under study are superior to classical graphene with respect to excitation of electromagnetic waves.     

Effect of magnetic field on nonlinear interactions of electromagnetic and surface waves in a plasma layer

Investigation is made for nonlinear interaction between incident radiation and a surface wave in a magnetized plasma layer. Both interacting waves are ofP polarization. We get the generated currents and fields at combination frequencies analytically. Unlike theS-polarized interacting waves, the magnetic field affects the fundamental waves and leads to an amplification of generated waves when their frequencies approach the cyclotron frequency.     

Inverse problem of reflection of electromagnetic waves from layered inhomogeneous plasma-like structures with refractive-index discontinuity

To reconstruct the distribution of free carriers in a layered inhomogeneous plasma-like half-space during the electromagnetic-wave reflection, we derive the Gelfrand-Levitan-Marchenko integral equation for structures with refractive-index discontinuity by the inverse problem method. Exact model solutions of the generalized equations are analyzed. The applicability limits and scope of these exact solutions for reconstruction problems are shown. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 50, No. 1, pp. 31–39, January 2007