Showing papers on "Electromagnetic field published in 2022"

Nonoverflow Representation of Electromagnetic Field From Dipole Source in Cylindrical Media With Uniaxial Anisotropy

Abstract: A nonoverflow representation of the electromagnetic (EM) field radiated by dipole sources in the cylindrical multilayered anisotropic media is presented. The sources include both magnetic and electric triaxial dipoles. The permeability, permittivity, and conductivity of each layer are all uniaxial anisotropic. A set of normalized reflection/transmission coefficients is defined and utilized to describe the propagation of EM wave. The recursive algorithm of EM field in each layer is with respect to the ratios of the outgoing and standing waves. In the expressions, all the Hankel or Bessel functions are in the form of their ratios, which avoid the overflow problem in numerical integral. To improve the stability and accuracy of numerical calculation, we subtract the background field from the total field in spectral domain. The background field is calculated by the algebraic solution in spatial domain rather than its integral representation. The rest of the field, namely the reflection field, has a smaller convergence region compared with its total field, and is calculated using the cubic spline interpolation method. The parities of the integrand are discussed by using numerical simulations, which yield the corresponding folded expressions of the field components to accelerate the computational efficiency. This work can be widely used in the applications of geophysical exploration.

Spoof surface plasmon photonics

Abstract: Structuring metallic surfaces allows for the support of surface electromagnetic modes at frequencies for which they would not be allowed for smooth surfaces. These modes are called ``spoof surface plasmons'' because of their similarity to surface plasmons that are supported at optical frequencies for smooth surfaces. This article describes the physics that underlies the behavior of spoof surface plasmons and how these modes are used in applications that require the manipulation of electromagnetic fields at frequencies below optical.

Theoretical Challenges in Polaritonic Chemistry

Abstract: Polaritonic chemistry exploits strong light-matter coupling between molecules and confined electromagnetic field modes to enable new chemical reactivities. In systems displaying this functionality, the choice of the cavity determines both the confinement of the electromagnetic field and the number of molecules that are involved in the process. While in wavelength-scale optical cavities the light-matter interaction is ruled by collective effects, plasmonic subwavelength nanocavities allow even single molecules to reach strong coupling. Due to these very distinct situations, a multiscale theoretical toolbox is then required to explore the rich phenomenology of polaritonic chemistry. Within this framework, each component of the system (molecules and electromagnetic modes) needs to be treated in sufficient detail to obtain reliable results. Starting from the very general aspects of light-molecule interactions in typical experimental setups, we underline the basic concepts that should be taken into account when operating in this new area of research. Building on these considerations, we then provide a map of the theoretical tools already available to tackle chemical applications of molecular polaritons at different scales. Throughout the discussion, we draw attention to both the successes and the challenges still ahead in the theoretical description of polaritonic chemistry.

Breakdown of topological protection by cavity vacuum fields in the integer quantum Hall effect

Abstract: The prospect of controlling the electronic properties of materials via the vacuum fields of cavity electromagnetic resonators is emerging as one of the frontiers of condensed matter physics. We found that the enhancement of vacuum field fluctuations in subwavelength split-ring resonators strongly affects one of the most paradigmatic quantum protectorates, the quantum Hall electron transport in high-mobility two-dimensional electron gases. The observed breakdown of the topological protection of the integer quantum Hall effect is interpreted in terms of a long-range cavity-mediated electron hopping where the anti-resonant terms of the light-matter coupling Hamiltonian develop into a finite resistivity induced by the vacuum fluctuations. Our experimental platform can be used for any two-dimensional material and provides a route to manipulate electron phases in matter by means of vacuum-field engineering.

Charged particle motion and radiation in strong electromagnetic fields

Abstract: The dynamics of charged particles in electromagnetic fields is an essential component of understanding the most extreme environments in our Universe. In electromagnetic fields of sufficient magnitude, radiation emission dominates the particle motion and effects of nonlinear quantum electrodynamics (QED) are crucial, which triggers electron-positron pair cascades and counterintuitive particle-trapping phenomena. As a result of recent progress in laser technology, high-power lasers provide a platform to create and probe such fields in the laboratory. With new large-scale laser facilities on the horizon and the prospect of investigating these hitherto unexplored regimes, we review the basic physical processes of radiation reaction and QED in strong fields, how they are treated theoretically and in simulation, the new collective dynamics they unlock, recent experimental progress and plans, as well as possible applications for high-flux particle and radiation sources.

Coupling of mechanical deformation and electromagnetic fields in biological cells

Abstract: A distinctive characteristic of the biological cell is its ability to mechanically deform to crawl or squeeze through trapped spaces. When a cell is taken apart, the structural deformation of its cellular components as biological matter can be manipulated by electrical and magnetic fields. Their response to the external fields opens an opportunity for biomedical intervention of controlling the movement of a cell. The understanding of the coupling between the mechanical deformation and the nonlinear electromagnetic behavior, however, requires the formulation of electrostatics and continuum mechanics in elastic material. This review reports on several major advances in elucidating the physics of biological matter and surveys new challenges pertinent to cellular biomechanics.

Intrinsic Optical Spatial Differentiation Enabled Quantum Dark-Field Microscopy.

Abstract: By solving the Maxwell's equations in Fourier space, we find that the cross-polarized component of the dipole scattering field can be written as the second-order spatial differentiation of the copolarized component. This differential operation can be regarded as intrinsic which naturally arises as consequence of the transversality of electromagnetic fields. By introducing the intrinsic spatial differentiation into heralded single-photon microscopy imaging technique, it makes the structure of pure-phase object clearly visible at low photon level, avoiding any biophysical damages to living cells. Based on the polarization entanglement, the switch between dark-field imaging and bright-field imaging is remotely controlled in the heralding arm. This research enriches both fields of optical analog computing and quantum microscopy, opening a promising route toward a nondestructive imaging of living biological systems.

Incomplete electromagnetic response of hot QCD matter

Abstract: The electromagnetic response of hot QCD matter to decaying external magnetic fields is investigated. We examine the validity of Ohm's law and find that the induced electric current increases from zero and relaxes towards the value from Ohm's law. The relaxation time is larger than the lifetime of the external magnetic field for the QCD matter in relativistic heavy-ion collisions. The lower-than-expected electric current significantly suppresses the induced magnetic field and makes the electromagnetic response incomplete. We demonstrate the incomplete electromagnetic response of hot QCD matter by calculations employing the parton transport model combined with the solution of Maxwell's equations. Our results show a strong suppression by two orders of magnitude in the magnetic field relative to calculations assuming the validity of Ohm's law. This may undermine experimental efforts to measure magnetic-field-related effects in heavy-ion collisions.Received 5 November 2021Revised 21 February 2022Accepted 18 March 2022DOI:https://doi.org/10.1103/PhysRevC.105.L041901Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasNuclear matterQuark-gluon plasmaRelativistic heavy-ion collisionsNuclear PhysicsParticles & Fields

Recent progress on optomagnetic coupling and optical manipulation based on cavity-optomagnonics

Abstract: Abstract Recently, the photon—magnon coherent interaction based on the collective spins excitation in ferromagnetic materials has been achieved experimentally. Under the prospect, the magnons are proposed to store and process quantum information. Meanwhile, cavity-optomagnonics which describes the interaction between photons and magnons has been developing rapidly as an interesting topic of the cavity quantum electrodynamics. Here in this short review, we mainly introduce the recent theoretical and experimental progress in the field of optomagnetic coupling and optical manipulation based on cavity-optomagnonics. According to the frequency range of the electromagnetic field, cavity optomagnonics can be divided into microwave cavity optomagnonics and optical cavity optomagnonics, due to the different dynamics of the photon—magnon interaction. As the interaction between the electromagnetic field and the magnetic materials is enhanced in the cavity-optomagnonic system, it provides great significance to explore the nonlinear characteristics and quantum properties for different magnetic systems. More importantly, the electromagnetic response of optomagnonics covers the frequency range from gigahertz to terahertz which provides a broad frequency platform for the multi-mode controlling in quantum systems.

Tailoring electromagnetic responses in a coupled-grating system with combined modulation of near-field and far-field couplings

Abstract: Herein, we establish a hybrid coupling model (HCM) containing both near- and far-field couplings to describe the electromagnetic response of the coupled-grating system composed of two parallelly aligned subwavelength dielectric gratings. The HCM shows that the near-field coupling strength only contributes to the frequency splitting of two resonant modes, while the far-field one contributes to the frequency splitting and the linewidths of two resonant modes simultaneously. By changing the distance between two dielectric gratings, both the near- and far-field coupling strengths can be flexibly tuned, giving rise to rich electromagnetic responses. In addition, the formation of Fabry-Perot bound states in the continuum in coupled-grating systems can be clearly explained by the HCM. In this paper, we not only provide an all-dielectric platform for simultaneously manipulating near- and far-field couplings but also offer a viable approach to achieve reflectance/transmittance spectra with diverse shapes.

Maximally symmetric nonlinear extension of electrodynamics and charged particles

Abstract: We consider couplings of electrically and magnetically charged sources to the maximally symmetric non-linear extension of Maxwell's theory called ModMax. The aim is to reveal physical effects which distinguish ModMax from Maxwell's electrodynamics. We find that, in contrast to generic models of non-linear electrodynamics, Lienard-Wiechert fields induced by a moving electric or magnetic particle, or a dyon are exact solutions of the ModMax equations of motion. We then study whether and how ModMax non-linearity affects properties of electromagnetic interactions of charged objects, in particular the Lorentz force, the Coulomb law, the Lienard-Wiechert fields, Dirac's and Schwinger's quantization of electric and magnetic charges, and the Compton Effect. In passing we also present an alternative form of the ModMax Lagrangian in terms of the coupling of Maxwell's theory to axion-dilaton-like auxiliary scalar fields which may be relevant for revealing the effective field theory origin of ModMax.

Wireless Electromagnetic Radiation Assessment Based on the Specific Absorption Rate (SAR): A Review Case Study

Abstract: Employing electromagnetic fields (EMFs) in new wireless communication and sensing technologies has substantially increased the level of human exposure to EMF waves. This paper presents a useful insight into the interaction of electromagnetic fields with biological media that is defined by the heat generation due to induced currents and dielectric loss. The specific absorption rate (SAR) defines the heating amount in a biological medium that is irradiated by an electromagnetic field value. The paper reviews the radio frequency hazards due to the SAR based on various safety standards and organisations, including a detailed investigation of previously published work in terms of modelling and measurements. It also summarises the most common techniques utilised between 1978 and 2021, in terms of the operational frequency spectrum, bandwidth, and SAR values.

Shaping Electromagnetic Fields with Irregular Metasurface

Abstract: The electromagnetic scattering of an object is directly related to its physical geometry and material properties. While metasurfaces show excellent performances in mimicking material properties almost at well by flexibly designing meta‐atoms with arbitrary electromagnetic responses, their physical geometries are generally in a regular manner. The break of a metasurface's geometry will inevitably affect its electromagnetic scattering that introduces uncertainty in wavefront manipulation. Here, a general approach for highly efficient wavefront manipulation with irregular shaped metasurfaces is proposed. Such an approach establishes a universal iterative modulation relation between the metasurface and scattered field by introducing boundary constraints at the aperture, enabling to deal with the electromagnetic scattering from a metasurface with arbitrary spatial shape. In this way, the desired wavefront form can be engineered using meta‐atom sequences with arbitrarily shaped aperture. As a proof of concept, a flower‐shaped metasurface operating in the reflection mode is designed and experimentally demonstrated for reconstructing four random focuses with uniform and high‐efficiency intensity distribution at near‐field region, while the flower shaped field pattern can be extracted near the aperture plane. Such a method may pave a new route for advanced wavefront manipulation and electromagnetic concealment/camouflage applications.

Physical units to report intensity of electromagnetic wave

Abstract: The aim of this work is to propose a consensus to scientific community that handles personal exposimeters, which measure intensity of an electromagnetic wave (W/m2). To express the intensity of an electromagnetic wave there is a duality in the way of expressing it. Some scientists prefer to use W/m2 while others use V/m, which is a unit of the electric field. There is also a duality in the name, sometimes it is called it power flux density and some other times, wave intensity. We believe that this second name is more appropriate from the point of view of physics. We suggest expressing intensity of an electromagnetic wave in W/m2 instead of giving the value of their electric field which is measured in V/m. There is a quadratic relation between electric field and intensity of the wave, and it is necessary to do a mathematical operation, so in our opinion, it is preferable to use W/m2 which directly gives us the value of the measured intensity. Furthermore, if the intensity is very low, it may be expressed in μW/m2 and with only three significant figures, due to sensitivity of the current exposimeters used.

Algebras of integrals of motion for the Hamilton–Jacobi and Klein–Gordon–Fock equations in spacetime with four-parameter groups of motions in the presence of an external electromagnetic field

Abstract: The algebras of the integrals of motion of the Hamilton–Jacobi and Klein–Gordon–Fock equations for a charged test particle moving in an external electromagnetic field in a spacetime manifold are found. The manifold admits four-parameter groups of motions that act nontransitively on the spacetime. All admissible electromagnetic fields for which such algebras exist are found. In the case of an arbitrary n-dimensional Riemannian space on which the groups of motions act, it is proved that the admissible field does not deform the algebra of symmetry operators of the free Hamilton–Jacobi and Klein–Gordon–Fock equations. In addition, the system of differential equations, which must be satisfied by the potentials of the admissible electromagnetic field, has been investigated for compatibility.

Maxwell’s Equations in Homogeneous Spaces for Admissible Electromagnetic Fields

Abstract: Maxwell’s vacuum equations are integrated for admissible electromagnetic fields in homogeneous spaces. Admissible electromagnetic fields are those for which the space group generates an algebra of symmetry operators (integrals of motion) that is isomorphic to the algebra of group operators. Two frames associated with the group of motions are used to obtain systems of ordinary differential equations to which Maxwell’s equations reduce. The solutions are obtained in quadratures. The potentials of the admissible electromagnetic fields and the metrics of the spaces contained in the obtained solutions depend on six arbitrary time functions, so it is possible to use them to integrate field equations in the theory of gravity.

Parallel Higher Order DGTD and FETD for Transient Electromagnetic-Circuital-Thermal Co-Simulation

Abstract: A hybrid higher order discontinuous Galerkin time-domain (DGTD) method and finite-element time-domain (FETD) method with parallel technique is proposed for electromagnetic (EM)–circuital–thermal co-simulation in this article. For electromagnetic simulation, DGTD method with higher order hierarchical vector basis functions is used to solve Maxwell equation. Circuit simulation is carried out by modified nodal analysis method. For thermal simulation, FETD method with higher order interpolation scalar basis functions is adopted to solve heat conduction equation. To implement electromagnetic–circuital–thermal co-simulation, the electromagnetic and circuital equations are strongly coupled through voltages, currents, and electric fields at the lumped ports first. Then the electromagnetic and thermal equations are weakly coupled with electromagnetic loss and temperature-dependent medium parameters. Finally, large-scale parallel technique is used to accelerate the process of multiphysics simulation. Numerical results are given to validate the correctness and capability of the proposed electromagnetic–circuital–thermal co-simulation method.

Pseudogauges and relativistic spin hydrodynamics for interacting Dirac and Proca fields

Abstract: We present the explicit expressions of different pseudo-gauge transformations for Dirac and Proca fields considering a general interaction term. The particular case of the interaction of Dirac and Proca fields with a background electromagnetic field is also studied. Starting from the quantum kinetic theory with collisions derived from the Wigner-function formalism for massive spin-1/2 and spin-1 particles, we establish a connection between different pseudo-gauges and relativistic spin hydrodynamics. The physical implications of the various decompositions of orbital and spin angular momentum are discussed.

Quasinormal modes of charged black holes with corrections from nonlinear electrodynamics

Abstract: We study quasinormal modes related to gravitational and electromagnetic perturbations of spherically symmetric charged black holes in nonlinear electrodynamics. Beyond the linear Maxwell electrodynamics, we consider a class of Lagrangian with higher-order corrections written by the electromagnetic field strength and its Hodge dual with arbitrary coefficients, and we parametrize the corrections for quasinormal frequencies in terms of the coefficients. It is confirmed that the isospectrality of quasinormal modes under parity is generally violated due to nonlinear electrodynamics. As applications, the corrections for quasinormal frequencies in Euler-Heisenberg and Born-Infeld electrodynamics are calculated, then it is clarified that the nonlinear effects act to lengthen the oscillation period and enhance the damping rate of the quasinormal modes.

Optimization of Electromagnetic Metasurface Parameters Satisfying Far-Field Criteria

Abstract: Electromagnetic metasurfaces offer the capability to realize arbitrary power-conserving field transformations. These field transformations are governed by the generalized sheet transition conditions, which relate the tangential fields on each side of the surface through the surface parameters. Ideally, designers would solve for the surface parameters based on their application-specific far-field criteria. However, determining the surface parameters for these criteria is challenging without knowledge of the tangential fields on each side of the surface, which are not unique for a given far-field pattern. Current designs are generally restricted to analytical examples where the tangential fields can be solved for, or determined via ad hoc methods, although there has been recent work to circumvent this. This article presents an optimization scheme, which determines surface parameters, such as electric impedance, magnetic admittance, and magnetoelectric coupling, satisfying far-field constraints, such as beam level, sidelobe level, and null locations. The optimization is performed using a method of moments-based model incorporating edge effects and mutual coupling. The surface parameters are optimized for using the alternating direction method of multipliers. Examples of this optimization scheme performing multicriteria pattern forming, extreme angle small surface refraction, and Chebyshev-like beamforming are presented.

Engineering Electromagnetic Field Distribution and Resonance Quality Factor Using Slotted Quasi-BIC Metasurfaces.

Abstract: Dielectric metasurfaces governed by bound states in the continuum (BIC) are actively investigated for achieving high-quality factors and strong electromagnetic field enhancements. Traditional approaches reported for tuning the performance of quasi-BIC metasurfaces include tuning the resonator size, period, and structure symmetry. Here we propose and experimentally demonstrate an alternative approach through engineering slots within a zigzag array of elliptical silicon resonators. Through analytical theory, three-dimensional electromagnetic modeling, and infrared spectroscopy, we systematically investigate the spectral responses and field distributions of the slotted metasurface in the mid-IR. Our results show that by introducing slots, the electric field intensity enhancement near the apex and the quality factor of the quasi-BIC resonance are increased by a factor of 2.1 and 3.3, respectively, in comparison to the metasurface without slots. Furthermore, the slotted metasurface also provides extra regions of electromagnetic enhancement and confinement, which holds enormous potential in particle trapping, sensing, and emission enhancement.

Topology Optimization for Electromagnetics: A Survey

Abstract: The development of technologies for the additive manufacturing, in particular of metallic materials, is offering the possibility of producing parts with complex geometries. This opens up to the possibility of using topological optimization methods for the design of electromagnetic devices. Hence, a wide variety of approaches, originally developed for solid mechanics, have recently become attractive also in the field of electromagnetics. The general distinction between gradient-based and gradient-free methods drives the structure of the paper, with the latter becoming particularly attractive in the last years due to the concepts of artificial neural networks. The aim of this paper is twofold. On one hand, the paper aims at summarizing and describing the state-of-art on topology optimization techniques while on the other it aims at showing how the latter methodologies developed in non-electromagnetic framework (e.g., solid mechanics field) can be applied for the optimization of electromagnetic devices. Discussions and comparisons are both supported by theoretical aspects and numerical results.

A Unified View of Computational Electromagnetics

Abstract: This article presents a unified description of numerical methods for solving electromagnetic field problems. Traditionally, these methods are considered to be independent and alternative ways of solving Maxwell’s equations or equations derived therefrom. However, they all are projective approximations of the unknown solution by known expansion or basis functions with unknown amplitude coefficients that are determined using the so- called method of weighted residuals (MWR). This common feature forms the proposed unifying framework that may serve both as a systematic introduction to computational electromagnetics and as a way to provide insight into the nature, strengths, and limitations of the various algorithms used by present and future field solvers. For convenience, the fundamental equations and concepts of electromagnetics are summarized in order to facilitate the demonstration of the unified approach. Our aim is to provide students, designers, and researchers with a framework for developing new numerical algorithms, to guide users in the selection and application of electromagnetic design tools, and to foster informed engineering judgment. This article also serves as a review and summary of earlier theoretical works reported in different places and at different times.

Weak Coupling Technology With Noncoplanar Bucking Coil in a Small-Loop Transient Electromagnetic System

Abstract: Small-loop transient electromagnetic (TEM) method can be used for urban underground space detection. Given the mutual inductance between transmitting and receiving coils, the early secondary field signals are contaminated by primary field signals. To compensate for the primary field, bucking coil technology has been utilized in the airborne TEM system due to attractive features of the technology, which include a compensation effect and a strong coupling strength between the receiving coil and the underground body. However, many problems arise when the bucking coil technology is used directly in a ground small-loop TEM system. One is that the size of the receiving coil is limited, resulting in insufficient bandwidth; the other is that the bucking coil brings the near-field effect, which causes the loss of shallow information. To solve these problems, in this article, we propose a new TEM structure with noncoplanar bucking compensation. Compared with the traditional design, the new structure overcomes not only the near-field effect but also reduces the constraint of the receiving coil size. Furthermore, the approach can suppress the primary field coupling more effectively, and has a better fault tolerance for the installation accuracy. The simulation and field experiment results verify the effectiveness and practicability of the new structure.