Transformation Of Electromagnetic Waves Research Articles

Electrodynamic properties of a rectangular waveguide with a dielectric plate located in the center of its wide wall

A rectangular waveguide with a dielectric plate located in the E-plane is the basic element of devices for microwave heat treatment of sheet materials. In this regard, it is relevant to study the processes of propagation and transformation of electromagnetic waves in such a system. The purpose of the work is to study the influence of the transformation of the electromagnetic field in the air medium of a rectangular waveguide in the zone of propagation of the slow wave H10 on the distribution of electric field energy in the dominant wavelength range and determining the wavelength, at which its maximum value is reached. The range properties of the intrinsic electrodynamic parameters and the field structure of a rectangular waveguide with a dielectric plate located in the E-plane in the middle of its wide wall have been studied. The wavelength at which the maximum energy level of the electric field in the dielectric plate is achieved is determined. The results obtained can be used in the design of microwave heating devices for dielectric materials.

Microwave Space-Time-Modulated Metasurfaces

Over the past decade, static metasurfaces have proved to be low-profile and efficient apparatuses for transformation of electromagnetic waves. However, such metasurfaces are restricted by their reciprocal and time- and frequency-invariant responses. To overcome these restrictions, space-time-modulated metasurfaces have recently been introduced for versatile, reciprocal/nonreciprocal, and frequency translation of electromagnetic waves. These are capable of changing both the momentum and energy of the incident wave and provide functionalities that are far beyond the capabilities of conventional static and reciprocal metasurfaces. This Perspective provides a discussion on the unique functionalities of a microwave space-time-modulated metasurface. In particular, we review various techniques that have been recently used for the realization of metasurfaces introducing spatiotemporal decomposition, scattering and diffraction, digital coding, nonreciprocal transmission, serrodyne frequency translation, pure frequency conversion, parametric wave amplification, and multifunctional operations. Although the paper focuses on microwave space-time metasurfaces, the described concepts can inspire realization of their optical counterparts.

Transistor-Loaded Nonmagnetic Nonreciprocal Metasurfaces

Reciprocal metasurfaces represent prominent compact structures for bidirectional and frequency-invariant transformation of electromagnetic waves. However, their application to modern wireless communication are limited due to their reciprocal response and lack of a controllable, versatile and programmable mechanism. On the other hand, nonreciprocal metasurfaces are capable of steering electromagnetic waves unidirectionally, leading to functionalities that are far beyond the capabilities of conventional static metasurfaces. In addition, they are controllable and programmable through their active constituents. This paper provides an overview on recent progress and opportunities offered by transistor-loaded metasurfaces to break reciprocity, and discusses their potential for low-energy, compact, and integrated nonreciprocal devices and systems.

Electromagnetic wave transformation in an oscillator medium with growing density.

The model of a medium made of oscillators can describe various materials, including artificial ones made of meta-atoms. Here the transformation of an electromagnetic wave in such a medium with rapidly growing oscillator density is studied. The initial polariton is shown to be transformed not only into new polariton modes but also into natural oscillations of the existing and created oscillators. The oscillations produce zero net polarization but consume significant amount of the initial polariton energy. Although the boundary conditions at the temporal jump are sufficient to find the new polaritons, the description of the polarization oscillations requires integrating the material equations because the oscillations are uncoupled from the fields. Under some conditions, the spatial dependence of the amplitude of the oscillations can provide a snapshot of the electromagnetic field distribution at the moment of rapid density growth. Some subtle issues related to the continuity conditions at the density jump are also discussed.

A plasmonic lens based on coordinate transformation

With the development and maturity of nanofabrication technology, many nanostructures with specific electromagnetic characteristics and optical functions have been designed and demonstrated. Artificial materials with these special optical properties are known as metamaterials. In this paper, a metamaterial lens is proposed and characterized. After using the space transformation approach based on the coordinate transformation principles, the lens becomes anisotropic and inhomogeneous, thus realizing the regulation of electromagnetic waves. The electromagnetic wave transformation characteristics of the superlens are numerically analysed by irradiating a plane transverse wave with a wavelength of 300 nm onto a rectangular slab. The results show that the waveform of the incident light changes from plane waves to cylindrical after passing through the superlens. The validity of the superlens is verified by finite element method calculations.

Linear Transformation of Electromagnetic Waves in Large-Scale Axially Symmetric Trap

The results are presented from studies of the efficiency of the quasi-optical wave beam tunneling through the opacity region in the vicinity of the plasma cutoff surface in the inhomogeneous magnetoactive plasma in the geometry corresponding to a large-scale axially symmetric open trap. In this geometry, the distinctive features are considered of the linear transformation of normal waves in two cases: the transformation of the left-handed polarized wave, which is typical of the toroidal traps, and the transformation of the right-handed polarized waves, which is possible when the plasma density gradient is not orthogonal to the magnetic field. Different effects limiting the achievable transformation efficiency are studied, and the possible approaches to the transformation efficiency optimization are considered.

Влияние гиротропии на трансформацию электромагнитной волны в спиновую вблизи частот антирезонанса

Влияние гиротропии на трансформацию электромагнитной волны в спиновую вблизи частот антирезонанса

Model of Electro-Pulse Processing of Metals Melts

Questions of influence of nanosecond electromagnetic impulses on melts of metals are considered in the article. The analysis of action of impulses on electromagnetic hashing and thermal conditions of a melt showed their small influence. Mechanical (acoustic) action is chosen as the main one. Formulas and values for coefficients of transformation of electromagnetic field to the acoustic one for a number of metals are given. The transformation model in the form of the wave of current running on the radiator is offered. Comparison of action of electromagnetic impulses on melts showed that emergence of acoustic vibrations is the main thing. The theory of contactless transformation of electromagnetic waves in acoustic ones is considered. Comparison with experiments is given. The model of contact electro-pulse processing of metal melts in the form of transition of an electromagnetic wave to acoustic is offered. Acoustic waves change structure of a melt, condition of a crystallization of a melt and improve properties of the hardened metal.

Propagating plasmon in periodical graphene structure

The transformation of electromagnetic wave into propagating plasmon in periodical dual-grating-gated graphene with asymmetric unit cell structure is theoretically investigated. The conditions of cancelling the transmission of the electromagnetic wave through the graphene structure and Fabry-Perot blocking the reflection are applied. We found out optimal unit cell asymmetry for maximum transformation incident wave into plasmon modes with the wavevectors multiplied the inverse length of the structure period.

Влияние различных механизмов нагрева слоистого алюмосиликата на сорбционные процессы. Сообщение 1. Сорбция воды при тепловом и электромагнитном (СВЧ) нагреве монтмориллонита

Используется различный механизм нагрева монтмориллонита для повышения его адсорбционной способности: быстрый объёмный нагрев образца электромагнитным излучением СВЧ дециметрового диапазона с частотой 2,45 ГГц и традиционный поверхностный нагрев. Проведены дериватографические исследования, исследована кинетика сорбции воды, определена лимитирующая стадия процесса адсорбции молекул воды. Установлено значительное возрастание сорбционной ёмкости образца, предварительно обработанного в электромагнитном поле СВЧ, как результат его более глубокой дегидратации, и, как следствие, вероятного усиления кислотности его поверхности.

On the transformation of electromagnetic waves in a gravitational: possible experimental verification

On the transformation of electromagnetic waves in a gravitational: possible experimental verification

Electromagnetic wave propagation in spatially homogeneous yet smoothly time-varying dielectric media

We explore the propagation and transformation of electromagnetic waves through spatially homogeneous yet smoothly time-dependent media within the framework of classical electrodynamics. By modelling the smooth transition, occurring during a finite period τ, as a phenomenologically realistic and sigmoidal change of the dielectric permittivity, an analytically exact solution to Maxwell׳s equations is derived for the electric displacement in terms of hypergeometric functions. Using this solution, we show the possibility of amplification and attenuation of waves and associate this with the decrease and increase of the time-dependent permittivity. We demonstrate, moreover, that such an energy exchange between waves and non-stationary media leads to the transformation (or conversion) of frequencies. Our results may pave the way towards controllable light–matter interaction in time-varying structures.

The Exact Absorbing Conditions Method in the Analysis of Open Electrodynamic Structures: Circular and Coaxial Waveguides

The exact absorbing conditions (EAC) have been constructed and used for truncating an unbounded domain of computation in open initial boundary value problems, which describe space-time transformations of electromagnetic waves in axially symmetrical waveguides. The equivalence theorem is proved that gives grounds for rigorous theoretical justification of the EAC-method.

Basic Elements for Microfiber Photonics: Micro/Nanofibers and Microfiber Coil Resonators

The basic functional element of microfiber photonics is a microfiber coil resonator (MCR), which potentially can perform filtering, time delay, and nonlinear transformations of electromagnetic waves, as well as sensing of the ambient medium. The first experimental demonstration of an MCR has been recently performed by researchers of the OFS Laboratories (Optical Fiber Communication Conference 2007, Postdeadline paper PDP46). This paper follows up on the later publication presenting a brief introduction to the theory, transmission properties and applications of optical micro/nanofibers and MCRs. Fabrication of MCRs in air and in liquid is reported. For the MCR immersed in liquid, the Q-factor exceeding 60 000 is achieved.

RADIATION FROM SURFACE WITH PERIODIC BOUNDARY OF METAMATERIALS EXCITED BY A CURRENT

The rigorous modeling and analysis of electromagnetic wave transformation and radiation from the periodic boundary of metamaterial are presented. The nature of the phenomenon of resonant radiation and the influence of various parameters on it are investigated. The study is carried out with the objective of potential applications to antenna design. Simulated results show that very high directivity can be obtained and that beam steering can be achieved by adjusting proper parameters.

Nonlinear transformation of electromagnetic waves in suddenly created cold magnetized plasma: Longitudinal propagation

The transformation of a circularly polarized electromagnetic source wave in a suddenly created cold magnetized and weakly nonlinear plasma is considered. For the case of longitudinal propagation (a source wave propagating along an external static magnetic field) when the ion motion is neglected, a circularly polarized source wave splits into four longitudinal oscillating modes. In the case of a linearly polarized source wave due to the interaction between its right and left circularly polarized components additional stationary and traveling electron wave modes are created. Amplitude distributions of all created modes are determined in closed form and presented in corresponding diagrams for different values of source wave and electron cyclotron frequencies.

Energetics of electromagnetic wave transformation in a time-varying magnetoplasma medium.

The transformation of a circularly polarized electromagnetic wave in a magnetoplasma medium with increasing plasma density is considered. The wave propagates along the static magnetic field. Complete analysis, including ion motion, is given both for slow (compared to the wave frequency) and rapid ionization rate. In the case of slow temporal variation of the plasma density, a relation between the energy of the wave and its frequency, which is conserved during the plasma creation process (adiabatic invariant), is found. The existence of significant energy losses follows from the invariant. The dissipative mechanism is explained via consideration of the case of a sudden growth of plasma density in time from one value to another. It is shown that energy transforms into the kinetic energy of carriers, and preionization of the medium plays a principal role in the dissipation process. In the special case of a whistler wave, up to 50% of the energy may be transformed into an ion-cyclotron wave when dense plasma is rapidly created.

Transformation of a monochromatic plane wane by the pulse-periodic time modulation of an infinite medium

An exact solution to the problem of the transformation of a monochromatic plane wave by a finite train of equally spaced rectangular pulses of permittivity and conductivity of an infinite medium is considered. The permittivity pulse train is shifted relative to the conductivity pulse train by an arbitrary time. The problem is studied analytically in terms of the second-order Volterra integral equation describing the electromagnetic wave transformation in a medium with time-dependent parameters. The equation is solved using the resolvent technique. Expressions for the amplitude of the transformed electric field component for any time instant at any spatial point are derived and analyzed.

Three-dimensional FDTD simulation of electromagnetic wave transformation in a dynamic inhomogeneous magnetized plasma

A three-dimensional (3-D) finite-difference time domain (FDTD) algorithm is developed to study the transformation of an electromagnetic wave by a dynamic (time-varying) inhomogeneous magnetized plasma medium. The current density vector is positioned at the center of the Yee cube to accommodate the anisotropy of the plasma medium due to the presence of a static magnetic field. An appropriate time-stepping algorithm is used to obtain accurate solutions for arbitrary values of the collision frequency and the electron cyclotron frequency. The technique is illustrated by calculating the frequency shifts in a cavity due to a switched magnetoplasma medium with a time varying and space-varying electron density profile.

Transformation of Electromagnetic Waves of Complex Space-and-Time Configuration by Layered Electrodynamic Structures

Transformation of Electromagnetic Waves of Complex Space-and-Time Configuration by Layered Electrodynamic Structures