Dispersion properties of cyclotron waves in periodic semiconductor-insulator structures

The band spectrum of cyclotron waves propagating in a periodic layered semiconductor-insulator structure at an angle to an external magnetic field that is applied perpendicularly to the layers is calculated for two relationships between the characteristic frequencies of the semiconductor: ω_H>ω_P and ω_H<ω_P. The wave field distributions across the layers and over the period of the structure are analyzed. In both spectra, transmission bands arise when the conditions for dimensional resonance across the semiconductor layer are fulfilled. The graphic solution of the dispersion relation demonstrates that the cyclotron wave spectrum can be subdivided into two spectra of normal waves according to the Bloch wavenumbers of the periodic structure. The cases where the band spectra complement each other or overlap are considered.     

Dispersion relations for optical waves in amplifying periodic structures

The characteristics of optical waves in amplifying dielectric periodic nanostructures are studied. The formula for the dependence of the wave number on frequency, which comprises a photonic band gap and is valid for structures possessing a complex dielectric function, is obtained. It is shown that the gain is anomalously high at frequencies residing in the photonic band gap.     

In-plane propagation of millimeter waves in periodic magnetoactive semiconductor structures

Non-transmission bands of electromagnetic waves propagating along the layers in periodic structures are studied in the steady magnetic field perpendicular both to the uniaxis and the direction of propagation. The band control range (36÷75 GHz) inn-InSb/Al₂O₃ structures with the carrier densities 4 10¹³ ≤n ≤ 8 10¹⁴ cm⁻³ in magnetic fieldsB _o ≤ 2 T at temperatures 77 ≤T ≤ 200 K is found to agree with the calculated in the effective medium approximation. Attenuation down to −50 dB within the band is observed. The band lineshape is found to indicate additional effects related to the finite layer thickness and periodicity termination predicted by a more rigorous theory of dispersion.     

The Reflection of electromagnetic waves from almost periodic structures

We investigate the reflection of electromagnetic waves from structures charaterized by a spatially varying dielectric permittivity of an almost periodic nature. The reflection from almost periodic structures is compared and contrasted with the reflection from periodic structures. Paradoxically, it is found that almost periodic structures may prove superior to their periodic counterparts when these structures are used as filters. The major portion of this work was performed while the author was with the California Institute of Technology, Pasadena, California 91125, USA     

Modulational instability of electromagnetic waves in birefringent fibers with periodic and random dispersion

Modulational instability (MI) of electromagnetic waves in a birefringent fiber with a periodic dispersion (two-step dispersion management scheme) is investigated. The properties of new sidebands are studied. The strong variation of dispersion leads to the decreasing of the main MI region and the suppression of additional resonance. In the random dispersion case the MI of all frequencies of modulation in the normal dispersion region is predicted. In the anomalous dispersion case the decreasing of the main MI peak is calculated and changes in the spectral bandwidth of MI gain are found. The analytical predictions are confirmed by the numerical simulations of the full coupled nonlinear Schr?dinger equations with periodic coefficients.     

Mathematical modeling of diffraction electromagnetic waves by curvilinear periodic structures

The problem of diffraction H—polarized plane waves by an ideally conducting infinite cylinder—has been investigated. The numerical experiments, based on solving integral equations by the method of auxiliary spline currents, show that it is possible to reduce the integral radar cross section of the cylinder by modulating its directrix. There is evidence of similarity between the results obtained and a well-known natural phenomenon. The text was submitted by the authors in English.     

Dispersion characteristics of spin waves in planar periodic structures based on ferromagnetic films

A technique for calculating the dispersion characteristics of planar periodic magnetic structures is suggested. It is based on joint application of the spin-wave mode analytical approach and the transfer matrix formalism. The dispersion characteristics of a planar periodic waveguiding medium representing a thin ferromagnetic film with an array of metallic strips (metallic grating) on its surface are calculated. It is shown that the dispersion characteristics of planar periodic structures based on ferromagnetic films depend, not only on the geometry of the waveguiding system, but also on the surface anisotropy of the initial film.     

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.     

Dispersion relation for electromagnetic waves in anisotropic media

Electromagnetic wave propagation in anisotropic dielectric media with two generic matrices εij and μij of permittivity and permeability is studied. In the framework of a metric-free electrodynamics approach, a compact tensorial dispersion relation is derived. The derivation does not require the corresponding matrices to be symmetric, positive definite, nor even invertible. The resulting formula is useful for a theoretical and experimental study of electromagnetic wave propagation in a wide class of linear media.     

Optical phonon interaction effects in layered semiconductor structures

Various aspects of the electron-LO-phonon interaction effects on the electronic properties of a single two-dimensional electron layer (as occurring, for example, in artificially structured single quantum wells or heterojunctions made of III–V or II–VI semiconducting materials) are discussed theoretically. In particular, perturbation theory is carried to the second order in the coupling constant to obtain the two-dimensional polaron energy in the weak-coupling limit. Intermediate coupling (the so-called Lee-Low-Pines theory) and strong coupling theories for the two-dimensional polaron problem are developed and interpolation (Padé approximations) formulae valid for arbitrary coupling are derived. Effects of the band non-parabolicity and of the free-carrier screening on the weak-coupling theory are discussed. The real and the imaginary parts of the two-dimensional polaron self-energy are obtained in a many-body perturbation calculation. Comparison with the known three-dimensional results is made wherever possible, showing that the electron-LO-phonon interaction effects are substantially enhanced in confined structures. Explicit formulas valid for two-dimensional systems are given for various polaron parameters like the binding energy, the effective mass, the scattering rate, the average phonon density in the polaron cloud, etc.     

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     

Dispersion process of electromagnetic waves in a moving medium

The propagation of electromagnetic waves in a moving isotropic plasma and in a moving magnetoactive plasma is considered using the invariant methods of tensor analysis. Expressions are obtained for the dielectric permittivity tensor, the dispersion equations, and the refractive indexes of electromagnetic waves in these media. Using these results it is possible to establish corrections to the angular displacement which occurs when radiation passes through a moving electron plasma.Published from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 1, pp. 121–129, January, 1996.