Diffraction Of Electromagnetic Waves Research Articles

Diffraction of electromagnetic waves by a resistive half‐plane in magneto‐ionic plasma

AbstractThe interaction of magnetic polarized electromagnetic wave with a resistive half‐plane in magneto‐ionic plasma is investigated. The method of transition boundary is used for the evaluation of the diffracted wave. The excitation of surface waves is examined in the medium and their diffracted fields are derived by using the diffraction theory for grazing incidence. The uniform field expressions are obtained with the aid of the uniform theory for evanescent waves. The behaviours of the derived scattered waves are studied numerically.

Diffraction of Electromagnetic Waves by Multilayer Graphene Metasurfaces in the Terahertz Frequency Band

We perform mathematical modeling of diffraction of plane electromagnetic waves by multilayer metasurfaces comprised by elements of graphene nanoribbons. The modeling is based on solving the three-dimensional boundary value diffraction problem by three methods, specifically, those of self-contained units with Floquet channels, the volume integro-differential equation, and approximate boundary conditions. The coefficients of reflection, transmission, and absorption of s- and p-polarized waves by metasurfaces made of elements of rectangular graphene nanoribbons are calculated as functions of the frequency and the incidence angle for various values of the chemical potential with allowance for the geometric and dimensional effects in the terahertz frequency band. It is shown that at the resonant frequencies of the surface plasmon polariton, multilayer metasurfaces comprised by two graphene strips in an elementary cell on substrates, which contain layers of a dielectric and graphene, are electrically controlled efficient wideband terahertz absorbers and polarizers in the reflection regime that are insensitive to incidence angles.

Дифракция электромагнитных волн на композитной структуре «ленточная решетка – ферромагнитное полупространство»: резонансы на поверхностных волнах

Дифракция электромагнитных волн на композитной структуре «ленточная решетка – ферромагнитное полупространство»: резонансы на поверхностных волнах

Understanding diffraction grating behavior, part II: parametric diffraction efficiency of sinusoidal reflection (holographic) gratings

With the widespread availability of electromagnetic (vector) analysis codes for describing the diffraction of electromagnetic waves by periodic grating structures, the insight and understanding of nonparaxial parametric diffraction grating behavior afforded by approximate methods (i.e., scalar diffraction theory) is being ignored in the education of most optical engineers today. We show that the linear systems formulation of nonparaxial scalar diffraction theory enables the development of a scalar parametric diffraction grating model [for transverse electric (TE) polarization] for sinusoidal reflection gratings with arbitrary groove depths and arbitrary nonparaxial incident and diffracted angles. This scalar parametric analysis is remarkably accurate as it includes the ability to redistribute the energy from evanescent orders into the propagating ones, thus allowing the calculation of nonparaxial diffraction efficiencies to be predicted with an accuracy usually thought to require rigorous electromagnetic theory. These scalar parametric predictions of diffraction efficiency are compared to paraxial scalar and rigorous electromagnetic (vector) predictions for a variety of nonparaxial diffraction grating configurations, thus providing quantitative limits of applicability of nonparaxial scalar diffraction theory to sinusoidal reflection gratings as a function of the grating period-to-wavelength ratio (λ / <italic>d</italic>).

On the Electromagnetic Diffraction Propagation Model and Applications

Detection and localization of nonline-of-sight (NLOS) hidden target in complex urban environment is a very recent radar detection problem. In this article, we investigate the possibility of locating a target in a building corner NLOS region with a single-input single-output ultra-wideband radar by exploring the electromagnetic (EM) diffraction propagation path. The EM wave diffraction phenomenon referring to this single rectangular corner of the building is analyzed and the diffraction model in this scenario is established. Assuming that the geometric structure of the scenario is known earlier, we introduce an application of the destination location behind the corner based on the propagation of the EM wave diffraction. Finally, the numerical simulation and real data results demonstrate that a micromotion target and moving target can be localized exploiting the proposed approach.

Комбинированный радиопоглотитель на основе ферритового слоя и решеток резистивных квадратов

A radar absorbing structure shielding a metal plane in the form of a ferrite layer with a dielectric layer containing grids of resistive squares is considered. The problem of diffraction of a plane electromagnetic wave, normally incident on the structure, is solved. On the basis of the solution of the optimization problem, it is shown that in comparison with a simple ferrite layer, which is low-reflective only in the decimeter and meter wavelength ranges, the combined structure with a total thickness of less than 5 cm provides a small reflection in the region of centimeter waves.

Скорость переноса энергии плоской монохроматической электромагнитной волной через слой вещества

Рассмотрены стационарные задачи для прохождения (туннелирования) плоской электромагнитной волны через слой вещества с диэлектрическими свойствами, а также и квантовой частицы через прямоугольный потенциальный барьер. Показано, что сверхсветовых движений не возникает, а время прохождения всегда больше времени при прохождении структуры со скоростью света.

Diffraction of plane electromagnetic waves by a resistive half-screen for skew incidence.

The scattering process of electromagnetic plane waves by a resistive half-screen is investigated for oblique incidence. First of all, it is shown that the existing solution in the literature is not correct, because the problem was solved by considering the normal components of the electromagnetic field, in terms of which the boundary conditions cannot be expressed. Instead of these, the components of the electric field, which is parallel to the edge discontinuity, are taken into account. The diffracted fields are obtained with the aid of the method of transition boundary. The uniform field expressions are obtained by using the Fresnel function. The behaviors of the total field and its subcomponents are analyzed numerically.

Development of a software package for modeling and analysis of light diffraction on periodic structures of nanophotonics by the rigorous coupled-wave analysis

We discuss the development of a software package, which enables simulating and analyzing the diffraction of a plane electromagnetic wave on a multilayer diffraction grating with. The main functional requirements to the system are formulated. The architectural solution of the implemented software including the main functional and logical layers of the system with the specified methods of their interaction is described. The method allowing one to model light diffraction on multilayer diffraction structures comprising homogeneous layers and diffraction gratings with one-dimensional periodicity is implemented. A polarizing reflector consisting of a diffraction grating on a Bragg grating (a one-dimensional photonic crystal) consisting of a small number of layers is designed and investigated. The optimal parameters of the structure are found for a given reflectance criterion. The parameter ranges satisfying the chosen criterion are investigated. The influence of changes in the geometric parameters of the structure on the reflector performance is discussed. The designed software package is promising for the design of grating-based nanophotonic filters and sensors.

Coupled Plasmon Oscillations in a Cluster Consisting of Three Silver Nanocylinders with Different Diameters

2D problem of the diffraction of the TM plane electromagnetic wave by a cluster consisting of three self-similar silver nanocylinders with different sizes is considered. Rigorous numerical procedures are used to study quasi-static plasmon resonances in such a cluster. Frequency characteristics of the scattering cross section and spatial structure of the field in the vicinity of the cylinders are calculated for different angles of incidence of the plane wave, self-similarity coefficients, and diameters of cylinders. It is shown that an increase in the distance between the cylinders is accompanied by degeneration of the resonances of scattering cross section. When real loss of silver is taken into account, electric field at the exit of the cluster cannot be amplified by a factor of greater than 10.

Infinite Sets of Linear Algebraic Equations in the Problems of Diffraction of Electromagnetic Waves by the Non-Coordinate Periodic Media Interfaces

The diffraction problem of plane electromagnetic wave by the non-coordinate periodic media interface is reduced to an infinite set of linear algebraic equations for Floquet coefficients of scattered field. Two-dimensional case of diffraction problem is considered in detail. In the three-dimensional case, special attention is paid to problems of program implementation of algorithms of approximate solving of ISLAE.

Understanding diffraction grating behavior: including conical diffraction and Rayleigh anomalies from transmission gratings

With the wide-spread availability of rigorous electromagnetic (vector) analysis codes for describing the diffraction of electromagnetic waves by specific periodic grating structures, the insight and understanding of nonparaxial parametric diffraction grating behavior afforded by approximate methods (i.e., scalar diffraction theory) is being ignored in the education of most optical engineers today. Elementary diffraction grating behavior is reviewed, the importance of maintaining consistency in the sign convention for the planar diffraction grating equation is emphasized, and the advantages of discussing “conical” diffraction grating behavior in terms of the direction cosines of the incident and diffracted angles are demonstrated. Paraxial grating behavior for coarse gratings (<italic>d</italic> ≫ λ) is then derived and displayed graphically for five elementary grating types: sinusoidal amplitude gratings, square-wave amplitude gratings, sinusoidal phase gratings, square-wave phase gratings, and classical blazed gratings. Paraxial diffraction efficiencies are calculated, tabulated, and compared for these five elementary grating types. Since much of the grating community erroneously believes that scalar diffraction theory is only valid in the paraxial regime, the recently developed linear systems formulation of nonparaxial scalar diffraction theory is briefly reviewed, then used to predict the nonparaxial behavior (for transverse electric polarization) of both the sinusoidal and the square-wave amplitude gratings when the +1 diffracted order is maintained in the Littrow condition. This nonparaxial behavior includes the well-known Rayleigh (Wood’s) anomaly effects that are usually thought to only be predicted by rigorous (vector) electromagnetic theory.

Generalized Space-Time-Periodic Diffraction Gratings: Theory and Applications

This paper studies the theory and applications of the diffraction of electromagnetic waves by space-time periodic (STP) diffraction gratings. We show that, in contrast with conventional spatially periodic grating, a STP diffraction grating produces spatial diffraction orders, each of which is formed by an infinite set of temporal diffraction orders. Such spatiotemporally periodic gratings are endowed with enhanced functionalities and exotic characteristics, such as asymmetric diffraction pattern, nonreciprocal and asymmetric transmission and reflection, and an enhanced diffraction efficiency. The theory of the wave diffraction by STP gratings is formulated through satisfying the conservation of both momentum and energy, and rigorous Floquet mode analysis. Furthermore, the theoretical analysis of the structure is supported by time and frequency domain FDTD numerical simulations for both transmissive and reflective STP diffraction gratings. Additionally, we provide the conditions for Bragg and Raman-Nath diffraction regimes for STP gratings. Finally, as a particular example of a practical application of the STP diffraction gratings to communication systems, we propose an original multiple access communication system featuring full-duplex operation. STP diffraction gratings are expected to find exotic practical applications in communication systems, especially for the realization of enhanced-efficiency or full-duplex beam coders, nonreciprocal beam splitters, nonreciprocal and enhanced-resolution holograms, and illusion cloaks.

Reducing Wing Observability to Radar using Microserrations at the Leading Edge

Serrations are found in nature on the leading edge (LE) of bird wings and whale flippers. These serrations reduce flight noise and improve aerodynamic performance. This has inspired LE serrations to be incorporated in the design of aircraft wings and turbine blades. LE of wings can contribute significantly to observability of aircraft by radar due to LE diffraction of horizontally polarized incident electromagnetic (EM) waves. Serrations at the wing LE can also be used to reduce observability to radar under such circumstances. In the present study, the method of equivalent currents is used to analyse the effect of microserrations on an infinitesimally thin metallic delta wing. It is shown that microserrations at the wing LE can be effectively used to control backscatter due to diffraction of EM waves at the wing LE. LE serrations, in general, work by introducing a randomness in the interaction of wing LE with incident fluid flow or EM field.

Electromagnetic grazing anomalies. Energy flux extrema

The diffraction of electromagnetic waves at the surface periodic structures accompanied by strong anomalous effects in different diffraction orders is considered in detail for high-contrast interfaces. We restrict discussion by the transverse magnetic polarization of the incident wave (the magnetic field is orthogonal to the plane of incidence) and the simplest geometry when the plane of incidence is orthogonal to the grating grooves. The most attention is devoted to the strong maxima and minima of the energy flux density accompanying specific grazing propagation of some diffraction order. Relation to other anomalies, both Rayleigh and the resonance ones is discussed as well.

Calculation of the Velocity of the Electromagnetic Field Propagation in a Medium with Inclusions

Two variants of the method of calculation of the electromagnetic field propagation velocity in a medium with inclusions are investigated. The multiple scattering theory based on the electromagnetic wave diffraction by spherical particles in a Q-layered lattice and by Q-particles located inside a waveguide along its axis is considered.

A Computational Design Framework for Efficient, Fabrication Error-Tolerant, Planar THz Diffractive Optical Elements

We demonstrate ultra-thin (1.5-3λ0), fabrication-error tolerant efficient diffractive terahertz (THz) optical elements designed using a computer-aided optimization-based search algorithm. The basic operation of these components is modeled using scalar diffraction of electromagnetic waves through a pixelated multi-level 3D-printed polymer structure. Through the proposed design framework, we demonstrate the design of various ultrathin planar THz optical elements, namely (i) a high Numerical Aperture (N.A.), broadband aberration rectified spherical lens (0.1 THz–0.3 THz), (ii) a spectral splitter (0.3 THz–0.6 THz) and (iii) an on-axis broadband transmissive hologram (0.3 THz–0.5 THz). Such an all-dielectric computational design-based approach is advantageous against metallic or dielectric metasurfaces from the perspective that it incorporates all the inherent structural advantages associated with a scalar diffraction based approach, such as (i) ease of modeling, (ii) substrate-less facile manufacturing, (iii) planar geometry, (iv) high efficiency along with (v) broadband operation, (vi) area scalability and (vii) fabrication error-tolerance. With scalability and error tolerance being two major bottlenecks of previous design strategies. This work is therefore, a significant step towards the design of THz optical elements by bridging the gap between structural and computational design i.e. through a hybrid design-based approach enabling considerably less computational resources than the previous state of the art. Furthermore, the approach used herein can be expanded to a myriad of optical elements at any wavelength regime.

Diffraction of electromagnetic waves due to a point source by a three part boundary satisfying perfect electromagnetic conductor conditions

Approximate analytical solution of point source diffraction from a strip satisfying a recently introduced boundary condition is presented in this paper. Both separated and interacted fields are computed separately and then related transformations are applied to obtain the field diffracted from a strip satisfying non-reciprocal boundary condition. The correctness of mathematical results is also verified graphically and a good agreement with the existing literature is observed.

Research of influence a physical carrier on the characteristics for four-element circular antenna array

The main problem arising in the development of mobile-based antenna arrays is the problem of taking into account the influence of the carrier body on the characteristics of such an antenna array. Pilotless vehicle are one of the most popular directions of modern aviation development. It is aimed to consider a quite simple in design four-element annular antenna array and to analyze the influence on the bearing direction finding characteristics of such a mobile carrier which is a pilotless vehicle. Theoretical consideration of the carrier body effect on the bearing direction finding errors is usually reduced to the problem of electromagnetic waves diffraction on conducting objects. Comparison of some absolute bearing direction finding errors obtained by the phase correlation method for the cases of placing the antenna array in free space and on the array carrier is given. The results of the calculation of the root-mean-square values dependence on the frequency, averaged over all the analyzed angles of the radio wave direction of arrival, are presented. The dependences of the root-mean-square value on the azimuth angle of the radio wave direction of arrival for the cases of the antenna array placement on the carrier body and in the free space averaged for all the analyzed signal frequencies were calculated.

On the Solvability of the Problem of Electromagnetic Wave Diffraction by a Layer Filled with a Nonlinear Medium

The problem of diffraction of a polarized electromagnetic wave by a layer filled with a nonlinear medium is considered. The layer is located between two half-spaces with constant permittivities. Two widely used types of nonlinearities: saturation nonlinearity and Kerr nonlinearity are considered. It is proved that the results on the solvability of the problems in these cases are qualitatively different: in the case of saturation nonlinearity, there are conditions under which the diffraction problem has a unique solution and, in the case of Kerr nonlinearity, the diffraction problem always has an infinite set of solutions. Analytical and numerical methods for solving this kind of problems are developed. Numerical results are presented.