Electromagnetic Wave Phenomena Research Articles

Electromagnetic effects on solitons propagation of the (3+1)-dimensional extended Zakharov-Kuznetsov dynamical model with applications

This paper investigates wave solutions and electromagnetic wave phenomena governed by the (3+1)-dimensional extended Zakharov-Kuznetsov equation (EZKE) utilizing the Sardar sub-equation method. With a focus on electromagnetic wave generation and propagation, we rigorously analyze fundamental properties, soliton solutions, and dynamic behaviors of the EZKE. Through this analytical technique, we unravel the complex interplay among various wave types, including solitary waves and electromagnetic structures, elucidating their formation mechanisms and interaction dynamics. Furthermore, we delve into the stability characteristics of the EZKE, enhancing our understanding of its mathematical and physical implications. Our findings not only contribute to theoretical insights into nonlinear wave phenomena in (3+1)-dimensional space but also hold practical significance in plasma physics, nonlinear optics, and electromagnetic wave propagation. This study advances the development of innovative wave manipulation and control techniques, with applications ranging from plasma confinement in fusion devices to the design of advanced photonic devices for telecommunications and sensing purposes.

Fundamental limits on radiative χ(2) second harmonic generation.

Recent advances in fundamental performance limits for power quantities based on Lagrange duality are proving to be a powerful theoretical tool for understanding electromagnetic wave phenomena. To date, however, in any approach seeking to enforce a high degree of physical reality, the linearity of the wave equation plays a critical role. In this manuscript, we generalize the current quadratically constrained quadratic program framework for evaluating linear photonics limits to incorporate nonlinear processes under the undepleted pump approximation. Via the exemplary objective of enhancing second harmonic generation in a (free-form) wavelength-scale structure, we illustrate a model constraint scheme that can be used in conjunction with standard convex relaxations to bound performance in the presence of nonlinear dynamics. Representative bounds are found to anticipate features observed in optimized structures discovered via computational inverse design. The formulation can be straightforwardly modified to treat other frequency-conversion processes, including Raman scattering and four-wave mixing.

Characterization of interaction phenomena of electromagnetic waves with metamaterials via microwave near-field visualization technique

A new practical imaging technique was presented for metamaterial characterization and investigation by visualizations of the magnetic microwave near-field (H-MWNF) distributions on a metamaterial's surface using the method of thermo-elastic optical indicator microscopy (TEOIM). ITO-based transparent and ceramic-based opaque metamaterial structures were designed for magnetic near-field visualization. Depending on the incident microwave field polarization, the TEOIM system allows the characterization of the metamaterial properties and microwave interaction behavior. The working principle of the periodic structures was investigated through numerical simulations, and the obtained results exhibited strong agreement when compared with experimental observations. Moreover, the visualization of the H-MWNF revealed the potential to characterize and evaluate the absorption and transmission properties effectively.

An Analytical Antenna Modeling of Electromagnetic Wave Propagation in Inhomogeneous Media Using FDTD: A Comprehensive Study.

This paper discusses the challenges in characterizing electromagnetic (EM) waves propagating through inhomogeneous media, such as reinforced cement concrete and hot mix asphalt. Understanding the EM properties of materials, including their dielectric constant, conductivity, and magnetic permeability, is crucial to analyzing the behavior of these waves. The focus of this study is to develop a numerical model for EM antennas using the finite difference time domain (FDTD) method, and to gain a deeper understanding of various EM wave phenomena. Additionally, we verify the accuracy of our model by comparing its results with experimental data. We analyze several antenna models with different materials, including the absorber, high-density polyethylene and perfect electrical conductors, to obtain an analytical signal response that is verified against the experimental response. Furthermore, we model the inhomogeneous mixture of randomly distributed aggregates and voids within a medium. We verify the practicality and reliability of our inhomogeneous models using experimental radar responses on an inhomogeneous medium.

Propagation of Compressional Alfvén Waves in a Magnetized Pair Plasma Medium

The reductive perturbation approach was used to explore the nonlinear propagation of fast (compressive) and slow (rarefactive) electron–positron (EP) magnetoacoustic (EPMA) modes in an EP plasma medium. The solitary wave solution of the Korteweg-de Vries (K-dV) equation is used to identify the basic properties of EP compressional Alfvén waves. It is shown that the fast (slow) EPMA mode is predicted to propagate as compressive (rarefactive) solitary waves. The basic features (i.e., speed, amplitude, and width) of the compressive (i.e., fast) EPMA waves are found to be completely different from those of rarefactive (i.e., slow) EPMA ones. It is also examined that hump (dip) shape solitary waves are found for the fast (slow) mode. The significance of our findings is in understanding the nonlinear electromagnetic wave phenomena in laboratory plasma and space environments where EP plasma may exist.

On the group velocity of whistling atmospherics

The dynamic spectrum of a whistling atmospheric is a signal of falling tone, and the group delay time of the signal as a function of frequency is formed as a result of propagation of a broadband pulse in a medium (magnetospheric plasma) with a quadratic dispersion law. In this paper, we show that for quadratic dispersion the group velocity is invariant under Galilean transformations. This means that, contrary to expectations, the group velocity is paradoxically independent of the velocity of the medium relative to the observer. A general invariance condition is found in the form of a differential equation. To explain the paradox, we introduce the concept of the dynamic spectrum of Green’s function of the path of propagation of electromagnetic waves from a pulse source (lightning discharge in the case of a whistling atmospheric) in a dispersive medium. We emphasize the importance of taking into account the motion of plasma in the experimental and theoretical study of electromagnetic wave phenomena in near-Earth space.

О групповой скорости свистящих атмосфериков

The dynamic spectrum of a whistling atmospheric is a signal of falling tone, and the group delay time of the signal as a function of frequency is formed as a result of propagation of a broadband pulse in a medium (magnetospheric plasma) with a quadratic dispersion law. In this paper, we show that for quadratic dispersion the group velocity is invariant under Galilean transformations. This means that, contrary to expectations, the group velocity is paradoxically independent of the velocity of the medium relative to the observer. A general invariance condition is found in the form of a differential equation. To explain the paradox, we introduce the concept of the dynamic spectrum of Green’s function of the path of propagation of electromagnetic waves from a pulse source (lightning discharge in the case of a whistling atmospheric) in a dispersive medium. We emphasize the importance of taking into account the motion of plasma in the experimental and theoretical study of electromagnetic wave phenomena in near-Earth space.

Modeling Electromagnetic Wave Phenomena in Large Quantum Systems: Formulation and Computational Costs

The quantum framework of the time-dependent density functional theory (TDDFT) for analyzing nanostructured devices is reviewed, and alternative methods for incorporating induced electromagnetic fields into the theory are discussed. To capture the retardation effects in larger electronic structures, the TDDFT equations can be formulated by applying the Lorenz gauge-fixing condition to the induced scalar and vector potentials (analogous to macroscopic formulations used in antenna theory). Evaluating the retarded potentials via radiation integrals, however, rapidly becomes the computational bottleneck within the TDDFT time-marching framework if done in a brute-force manner. This article demonstrates that 3D space or 4D space-time fast Fourier transform (FFT) schemes can be adopted to accelerate these computations and reduce the costs of evaluating the potentials below the typical computational bottleneck of TDDFT. Thus, FFT-accelerated Lorenz gauge retarded potentials become an attractive candidate for replacing the conventionally used electrostatic-induced scalar potential within TDDFT.

Electromagnetic Fields in a Time-Varying Medium: Exceptional Points and Operator Symmetries

In this article, we study the interactions of electromagnetic waves with a non-dispersive dynamic medium that is temporally dependent. Electromagnetic fields under material time-modulation conserve their momentum but not their energy. We assume a time-variation of permittivity, permeability, and conductivity, and derive the appropriate time-domain solutions based on the causality state at a past observation time. We formulate a time-transitioning state matrix and connect the unusual energy transitions of electromagnetic fields in time-varying media with the exceptional point theory. This state-matrix approach allows us to analyze further the electromagnetic waves in terms of parity and time-reversal symmetries and signify parity-time symmetric wave-states without the presence of a spatially symmetric distribution of gain and loss, or any inhomogeneities and material periodicity. This article provides a useful arsenal to study electromagnetic wave phenomena under time-varying media and points out novel physical insights connecting the resulting energy transitions and electromagnetic modes with exceptional point physics and operator symmetries.

Unified wave field retrieval and imaging method for inhomogeneous non-reciprocal media.

Acoustic imaging methods often ignore multiple scattering. This leads to false images in cases where multiple scattering is strong. Marchenko imaging has recently been introduced as a data-driven way to deal with internal multiple scattering. Given the increasing interest in non-reciprocal materials, both for acoustic and electromagnetic applications, a modification to the Marchenko method is proposed for imaging such materials. A unified wave equation is formulated for non-reciprocal materials, exploiting the similarity between acoustic and electromagnetic wave phenomena. This unified wave equation forms the basis for deriving reciprocity theorems that interrelate wave fields in a non-reciprocal medium and its complementary version. Next, these theorems are reformulated for downgoing and upgoing wave fields. From these decomposed reciprocity theorems, representations of the Green's function inside the non-reciprocal medium are derived in terms of the reflection response at the surface and focusing functions inside the medium and its complementary version. These representations form the basis for deriving a modified version of the Marchenko method to retrieve the wave field inside a non-reciprocal medium and to form an image, free from artefacts related to multiple scattering. The proposed method is illustrated at the hand of the numerically modeled reflection response of a horizontally layered medium.

Wideband Epsilon‐Near‐Zero Supercoupling Control through Substrate‐Integrated Impedance Surface

AbstractThe supercoupling phenomenon of electromagnetic wave through arbitrary shaped epsilon‐near‐zero (ENZ) material channels has attracted considerable attention recently, leading to numerous intriguing applications. It has been demonstrated that around the cutoff frequency of fundamental TE10 mode, waveguide behaves as the 2D homogenous ENZ material. However, for a given waveguide geometry, the ENZ operating bandwidth is inherently narrow and the center frequency is fixed. Here, a reconfigurable ENZ medium is proposed and experimentally demonstrated with a wideband‐tunable supercoupling effect by means of inserting a metasurface inside the waveguide, named as substrate‐integrated impedance surface (SIIS). With different insertion depth (which can be mechanically tuned) of SIIS, the ENZ supercoupling frequency can be precisely controlled. The proposed technique not only achieves wideband tuning of the ENZ supercoupling, especially to control the enhanced group delay of the electromagnetic waves, thereby offering a promising way toward for tunable slow‐light devices, such as light storage and processing components.

Electromagnetic Waves in a Time Periodic Medium With Step-Varying Refractive Index

In this paper, we study the interactions of electromagnetic waves with a non-dispersive dynamic medium that is temporally dependent. Electromagnetic fields under material time-modulation conserve their momentum but not their energy. We assume a time-variation of the permittivity, permeability and conductivity and derive the appropriate time-domain solutions based on the causality state at a past observation time. We formulate a time-transitioning state matrix and connect the unusual energy transitions of electromagnetic fields in time-varying media with the exceptional point theory. This state-matrix approach allows us to analyze further the electromagnetic waves in terms of parity and time-reversal symmetries and signify parity-time symmetric wave-states without the presence of a spatially symmetric distribution of gain and loss, or any inhomogeneities and material periodicity. This paper provides a useful arsenal to study electromagnetic wave phenomena under time-varying media and points out novel physical insights connecting the resulting energy transitions and electromagnetic modes with exceptional point physics and operator symmetries.

Elasticity of Nuclear Pasta

The elastic properties of neutron star crusts are relevant for a variety of currently observable or near-future electromagnetic and gravitational wave phenomena. These phenomena may depend on the elastic properties of nuclear pasta found in the inner crust. We present large-scale classical molecular dynamics simulations where we deform nuclear pasta. We simulate idealized samples of nuclear pasta and describe their breaking mechanism. We also deform nuclear pasta that is arranged into many domains, similar to what is known for the ions in neutron star crusts. Our results show that nuclear pasta may be the strongest known material, perhaps with a shear modulus of 10^{30} ergs/cm^{3} and a breaking strain greater than 0.1.

The classical and theoretical simulation for dominant radiated frequencies of plasma nanowire in presence of a long monopole antenna with long wavelength radiation

A theoretical model based on the classical theory for the simulation of scattering phenomena of long wavelength electromagnetic waves from plasma nanowires is investigated. A line source as a monopole antenna radiator is considered, which radiates with frequency ω in the vicinity of plasma nanowires parallel to the nanowire axis. A mathematical relation for resonance frequency is obtained. It is shown that in the resonance situation, plasma nanowires represent most of the response to the presence of electromagnetic waves. Mathematical computations are done for both the cold and warm approximations of plasma cases. The diagrams of the variation of resonance frequency versus the variation of temperature, geometrical dimension, and carrier density of plasma nanowires are presented. Also, a mathematical relation for subsidiary resonance frequency with considering two line sources with opposite charge is offered. The diagrams of subsidiary resonance frequency versus the variation of temperature, geometrical dimension, and carrier density of plasma nanowires are presented. It is shown that the presented model provides a color diagnostic system for the determination of size, the number, and distribution of nanowires immersed in a fluid based on their temperature and geometrical dimension.

A simple DPSS laser setup and experiments for undergraduates

Advanced optical concepts are often thought to be out of reach when it comes to an experimental demonstration for undergraduates and secondary school students. This is not always true. Here, we discuss the use of a diode-pumped solid state (DPSS) laser based on Nd:YVO4/KTP hybrid crystals, being also at the heart of many green laser pointers, to educate students on multiple modern optical concepts and applications thereof. This concerns not only nonlinear optics, e.g. second harmonic generation, but also laser physics and electromagnetic wave phenomena that occur if light interacts with matter. In this contribution we primarily describe the setup of the simple Nd:YVO4/KTP solid state laser system using hybrid crystals. The setup is integrated into our lab for undergraduates and school students. We show that various experiments on the topics mentioned above can be performed with affordable equipment while investigating some basic laser characteristics. By studying the influence of different surface roughness from various materials on the appearance of laser speckles, students get to know a modern laser application. Furthermore, we describe an experiment on the optical data transfer in free space optical communication: an additional experiment with a high motivational nature.

Theoretical Modeling of Average Force Acted on Nano Plasma Spheres in Presence of Radiation of Long Wavelength Point Source

Using the solutions of field equation, due to the electromagnetic wave scattering phenomena from a nano plasma sphere(NPS), the inserted force on nano plasma sphere is simulated. For this purpose, with using suitable Green’s function, the scattering phenomena of long wavelength electromagnetic waves from a nano plasma sphere will be investigated. A point electromagnetic source is considered in finite distance from the NPS. The computations will be generalized to two monopole point sources with the same strength but with opposite sign in two sides of sphere to simulating a NPS in presence of a plane electromagnetic wave. The resonance frequency and pattern scattering for these problems will be presented. The graphs of variations of inserted force with respect to wave frequency and geometrical dimension variations are presented.

Modeling of Dispersive Materials Using Dispersion Models for FDTD Application

A nonlinear optimization algorithm based on the Nelder Mead method is used to characterize the frequency dependent permittivity of 15 materials based on Lorentz, modified Lorentz, Drude and Lorentz-Drude models. The optimized model parameters are used to calculate the complex relative permittivity of each material and compare it with experimental data. In each case, a very good match is found between the optimized and experimental data over a long wavelength range. Comparative study of the models used for each material is performed based on accuracy, wavelength range of applicability and computational efficiency. The parameters presented can be used for computer simulation of electromagnetic wave phenomena involving these materials.

고속철도시스템에서 낙뢰로 인해 전차선에 유도되는 서지전압의 해석

Lightning is one of hazards affecting the rapid-transit railway system. There are two effects, which are direct lightning surge to electric car line and induced lightning surge. Protection methods for the direct lightning surge are studied with various occasions, however, study of induced lightning surge is insufficient in spite of a large or small effects. In this paper, it is analysed the way that serge voltage is induced to electric car line by lightning strikes. By modeling the propagation process and the coupling phenomenon of electromagnetic wave produced by lightning strikes, it is achieved to make integrative circuit model combined with existing electric car model. The study is conducted into three different waveform of electromagnetic wave produced by lightning; rectangular wave, double exponential distribution wave, triangle wave. It is also simulated that the inducing serge is coupled to electric car line in an arbitrary location. The simulation results in that, when rapidly changing rectangular wave is supplied, maximum power is induced to electric car line.

Detection of spatially limited high‐porosity layers using crosshole GPR signal analysis and full‐waveform inversion

AbstractHigh‐permittivity layers, related to high‐porosity layers or impermeable clay lenses, can act as low‐velocity electromagnetic waveguides. Electromagnetic wave phenomena associated with these features are complicated, not well known and not easy to interpret in borehole GPR data. Recently, a novel amplitude analysis approach was developed that is able to detect continuous low‐velocity waveguides and their boundaries between boreholes by using maximum and minimum positions of the trace energy profiles in measured GPR data. By analyzing waveguide models of different thickness, dip, extent, permittivity, and conductivity parameters, we extend the amplitude analysis to detect spatially limited or terminated waveguides. Waveguides that show high‐amplitude elongated wave trains are most probably caused by a change in porosity rather than a change in clay content. In a crosshole GPR data set from the Boise Hydrogeophysical Research Site, two terminated wave‐guiding structures were detected using the extended amplitude analysis. Information gained from the amplitude analysis improved the starting model for full‐waveform inversion which imaged the lateral extent and thickness of terminated waveguides with high resolution. Synthetic data calculated using the inverted permittivity and conductivity models show similar amplitudes and phases, as observed in the measured data, which indicates the reliability of the obtained models. Neutron‐Neutron logging data from three boreholes confirm the changes in porosity and indicate that these layers were high‐porosity sand units within low‐porosity, poorly sorted sand, and gravel units.

Shear and compressional dust Alfvén solitons in a magnetized plasma medium of opposite polarity dust

Shear and compressional dust Alfven solitons propagating in a medium of opposite polarity magnetized dust fluids have been theoretically studied by using the reductive perturbation method. The derivative nonlinear Shrodinger (DNLS) and Korteweg-de Vries (K-dV) equations, and their stationary solitonic solutions have been derived to identify the basic properties of shear and compressional dust Alfven solitons. It is found that the opposite polarity dust medium under consideration supports the shear and compressional dust Alfven solitons having new features with new (slow) time and (large) length scales. The basic features (amplitude and width) of the shear dust Alfven solitons are found to be significantly different from those of the compressional ones. The importance of our results in understanding the nonlinear (localized) electromagnetic wave phenomena in space environments and laboratory devices is briefly discussed.