Dispersion Of Electromagnetic Waves Research Articles

Optically tunable bianisotropy in a sphere made from an epsilon-near-zero material.

Bianisotropic media can be used to engineer absorbance, scattering, polarization, and dispersion of electromagnetic waves. However, the demonstration of a tunable light-induced bianisotropy at optical frequencies is still lacking. Here, we propose an experimentally feasible concept for a light-induced tunable bianisotropic response in a homogeneous sphere made of an epsilon-near-zero (ENZ) material. By exploiting the large linear absorption and the large possible intensity-dependent changes in the permittivity of ENZ materials, the direction-dependent scattering and absorption cross sections could be obtained. Our findings pave the way for further studies and applications in the optical regime requiring full dynamic control of the bianisotropic behavior.

Quadraxial metamaterial.

We study the dispersion of electromagnetic waves in a spatially dispersive metamaterial with Lorentz-like dependence of principal permittivity tensor components on the respective components of the wave vector performing the analysis of isofrequency contours. The considered permittivity tensor describes a triple non-connected wire medium. It is demonstrated that the metamaterial has four optic axes in the frequency range below the artificial plasma frequency. The directions of the optical axes do not depend on frequency and coincide with the diagonals of quadrants. The conical refraction effect is observed for all four optic axes.

Features of Scattering of a Plane Electromagnetic Wave on a Conductive Ball

The phenomenon of scattering of a plane electromagnetic wave on a nonmagnetoactive conductive ball is studied. The dispersion of electromagnetic waves inside the ball material is taken into account. A special case of that phenomenon (the radius of the ball is much smaller than the wavelength of the scattered wave) lies in the basis of the work of a spaser, which can have a wide range of important practical applications.

Casimir force induced by electromagnetic wave polarization in Kerr, G\xf6del and Bianchi\u2013I spacetimes

Electromagnetic waves propagation on either rotating or anisotropic spacetime backgrounds (such as Kerr and Gödel metrics, or Bianchi–I metric) produce a reduction of the magnitude of Casimir forces between plates. These curved spacetimes behave as chiral or birefringent materials producing dispersion of electromagnetic waves, in such a way that right– and left–circularly polarized light waves propagate with different phase velocities. Results are explicitly calculated for discussed cases. The difference on the wavevectors of the two polarized electromagnetic waves produces an abatement of a Casimir force which depends on the interaction between the polarization of electromagnetic waves and the properties of the spacetime.

Cerenkov-free RIP Maxwell solver: dispersionless along X

A semi-implicit finite-difference time-domain (FDTD) numerical Maxwell solver is presented for full electromagnetic Particle-in-Cell (PIC) codes for the simulations of plasma-based acceleration. The solver projects the volumetric Yee lattice into planes transverse to a selected axis (the particle acceleration direction) that makes the scheme quasi-one-dimensional. The fields positions build rhombi in plane (RIP) patterns. The RIP scheme uses a compact local stencil that makes it perfectly suitable for massively parallel processing via domain decomposition along all three dimensions. No global/local spectral methods are involved. The scheme removes the numerical dispersion of electromagnetic waves running parallel to the selected axis. The scheme shows no numerical Cerenkov instability (NCI).

X-dispersionless Maxwell solver for plasma-based particle acceleration

A semi-implicit finite difference time domain (FDTD) numerical Maxwell solver is developed for full electromagnetic Particle-in-Cell (PIC) codes for the simulations of plasma-based acceleration. The solver projects the volumetric Yee lattice into planes transverse to a selected axis (the particle acceleration direction). The scheme - by design - removes the numerical dispersion of electromagnetic waves running parallel the selected axis. The fields locations in the transverse plane are selected so that the scheme is Lorentz-invariant for relativistic transformations along the selected axis. The solver results in “Galilean shift” of transverse fields by exactly one cell per time step. This eases greatly the problem of numerical Cerenkov instability (NCI). The fields positions build rhombi in plane (RIP) patterns. The RIP scheme uses a compact local stencil that makes it perfectly suitable for massively parallel processing via domain decomposition along all three dimensions. No global/local spectral methods are involved.

Dispersion of electromagnetic waves in coaxial cylindrical rippled-wall waveguide including plasma layer

Electronic technologies, especially in the microwave and terahertz frequency ranges, including plasma show better interaction efficiency and higher output power as compared to apparatus with the vacuum. Also, in these frequency ranges, the plasma-filled high-power waveguides can support TE and TM modes. Therefore, in this study, the dispersion relation of electromagnetic (EM) waves in a new rippled-wall waveguide structure contain the plasma layer and coaxial dielectric geometry is numerically studied. The Maxwell equations and boundary conditions are employed to investigate and analyze the dispersion relation in TM mode for coaxial geometry dielectric rippled-wall waveguide contain the plasma layer. High-frequency radiations are observed from the proposed configuration. It is found that the frequency of the wave increases with a decrease in the corrugation amplitude and period. Moreover, a decrease in frequency is observed with an increase in dielectric radius and a decrease in plasma radius.

Manipulation of the dielectric properties of narrow-band gap material by an ultrashort laser pulse

The control of dielectric responses of narrow-band gap materials by an ultrashort laser pulse is investigated theoretically using time-dependent density functional theory, taking gallium phosphide as a concrete example. We demonstrate that, by using properly selected laser parameters an ultrashort laser pulse can induce reversible change of the electric and optical properties. The anisotropy of the transient permittivity of the material throughout the pulse duration can be enhanced so strongly that the dispersion of electromagnetic waves in the material becomes hyperbolic in some frequency interval with increasing laser energy. We describe the evolution of the transient permittivity throughout the duration of the laser pulse, pointing out to a fundamental possibility for applications of ultrafast all-optical signal processing and optical-field effect devices.

ON-OFF Body Ultra-Wideband (UWB) Antenna for Wireless Body Area Networks (WBAN): A Review

Ultra-wideband (UWB) technology can offer broad capacity, short-range communications at a relatively low level of energy usage, which is very desirable for wireless body area networks (WBANs). The involvement of the human body in such a device poses immense difficulties for both the architecture of the wearable antenna and the broadcast model. Initially, the bonding between the wearable antenna and the human body should also be acknowledged in the early stages of the design, so that both the potentially degrading output of the antenna as a consequence of the body and the possibility of exposure for the body may be handled. Next, the transmission path in WBAN is affected by the constant activity of the human body, leading to the time-varying dispersion of electromagnetic waves. Few researchers were interested in this field, and some substantial progress has recently been considered. On the other hand, this paper covered both wearable and Non-wearable UWB antenna designs and applications with respect to their substrate characteristics. Finally, this review prospectively exposes the upgraded developments of (ON-OFF) body antennas in the area of wearable and Non-wearable UWB and their implementations in the WBAN device and aims to evaluate the latest design features that inspire the performance of the antennas.

Hyperbolic Phonon Polariton Electroluminescence as an Electronic Cooling Pathway

AbstractEngineering of the cooling mechanism is of primary importance for the development of nanoelectronics. While radiation cooling is rather inefficient in current electronic devices, the strong anisotropy of 2D materials allows for enhanced efficiency because their hyperbolic electromagnetic dispersion near phonon resonances allows them to sustain much larger (≈105) number of radiating channels. In this review, radiation cooling in 2D materials is addressed. The hyperbolic dispersion of electromagnetic waves is presented, and how the spontaneous fluctuations in current in a 2D electronic channel can radiate thermal energy in its hyperbolic surrounding medium is described. Both the regime of thermal current fluctuations and out‐of‐equilibrium current fluctuations can be described within the same framework leading to superPlanckian thermal emission and electroluminescent cooling. A recent experimental investigation on graphene‐on‐hBN transistors using electronic noise thermometry is discussed. In high mobility semimetal‐like graphene at large bias, a steady‐state out‐of‐equilibrium situation is caused by Zener tunneling of electrons, opening a route for electroluminescence of hyperbolic electromagnetic modes. Electroluminescent cooling is particularly prominent once the Zener tunneling regime is reached: observed cooling powers are nine orders of magnitude larger than in conventional LEDs.

Empowered Layer Effects and Prominent Properties in Few‐Layer Metasurfaces

AbstractMetamaterials are 3D artificial structures proposed to surpass conventional natural materials and realize novel functions beyond traditional optical elements. Nevertheless, they are usually bulky and difficult to be fabricated. As 2D equivalents of metamaterials, metasurfaces have been proposed to overcome the drawbacks of metamaterials and fully control the polarization, amplitude, phase, and dispersion of electromagnetic waves. Relative to single‐layer metasurfaces that have limited controllability and functionality, few‐layer metasurfaces have more degrees of freedom and abundant layer effects to design novel devices and achieve high‐efficiency applications. This review is focused on the empowered layer effects and prominent properties in few‐layer metasurfaces, and some distinctive applications proposed in recent years are discussed. It is expected that few‐layer metasurfaces will provide a promising road toward the novel intelligent photonic devices, multifunctional devices, and integrated photonic devices.

Retaining hypothetical photon mass in atomic spectroscopy models

We revisit the formalism involved in atomic spectroscopy modeling under the assumption that the photon has a finite mass. Starting from the Proca Lagrangian, we build a Hamiltonian suitable for the calculation of line shapes and intensities. Two consequences of finite photon mass are: (i) a dispersion of electromagnetic waves propagating in free space; (ii) the occurrence of a longitudinal polarization state. We illustrate these effects by addressing the spontaneous emission of a massive photon by an excited atom. The Einstein A coefficient and the power spectrum are calculated as an example. If the photon has a finite mass, deviations to standard formulas are showed to occur at energies comparable to the mass energy. A discussion based on the current upper bound estimates for the photon mass is done.

Disorder Effect on the Transmission of Second Harmonic Waves in One-Dimensional Periodically Poled LiTaO<sub>3</sub>

One of the methods for calculating electromagnetic wave dispersion in multi-layer structures is the transfer matrix method. In this paper, we use the transfer matrix method for second harmonic generation in a nonlinear multilayer structure. The nonlinear photonic crystals investigated in this paper are as one-dimensional multi-layered structures including ferroelectric materials such as LiTaO3. Our goal is to investigate the effect of the disorder on the transmission spectrum of electromagnetic waves. Our results showed that positional disorder has different effects on the transmitting band and the gap band. The disorder in the transmitting band reduces the transmission coefficient of the waves and increases the transmission coefficient of the waves in the gap band. Such work has not yet been done on nonlinear photonic crystals producing the second harmonic.

Stimulated Brillouin scattering of terahertz electromagnetic pulses in paraelectrics

The nonlinear acoustoelectromagnetic phenomena in the terahertz (THz) range in the crystalline paraelectric SrTiO3 are investigated theoretically. The goal is to investigate an appearance of short THz electromagnetic (EM) pulses. The moderate cooling to the temperature T ≈ 77 K is considered. The resonant three-wave interaction of two counterpropagating EM THz waves with the longitudinal acoustic wave of the difference frequency is under investigation that is called the stimulated Brillouin scattering. This resonant interaction is due to the quadratic nonlinearity called electrostriction. The appearance of short EM pulses is possible when the input amplitudes of the signal EM wave are comparable with the pump amplitude and the duration of the input pulses is quite long. In the temporal scale associated with the EM wave propagation within a crystal, the cubic EM nonlinearity and the EM wave dispersion affect this three-wave resonant interaction. Under the development of the resonant nonlinear interaction, the modulation instability occurs that results in the complex and even chaotic wave modulation.

Dispersion behavior of electromagnetic wave near the resonance in 1D magnetized ferrite photonic crystals

In the present article, we have analyzed the dispersion of electromagnetic wave in the one dimensional magnetized ferrite photonic crystals near the resonance in the permeability of the constituent materials for transverse magnetization in the transverse electric mode. The dispersion relation is obtained by transfer matrix method. It is observed that in the vicinity of resonant frequency, large numbers of oscillations occur in the normalized Bloch wave number. These oscillations in the Bloch wave number are strongly dependent on external magnetic fields, filling factor, and damping constant. The frequency regime of these oscillations is found to be shifted in higher frequency range with increase in the magnitude of the magnetic fields. With increase in the filling factor keeping length of periods fixed, number of oscillations is found to be increased. Near the resonance, effect of incident angle is negligible. It is demonstrated that these nearly equidistant oscillations occurring in the vicinity of resonance may be used for making filter in micro wave frequency range.

A Theoretical Model of Dual Tunable Optoelectronic Oscillator

A theoretical model of an electronically tunable multi-loop optoelectronic oscillator (OEO) based on photonic and microwave multiferroic delay lines has been developed. The theory takes into account a dispersion of electromagnetic waves in optical fibers and a dispersion of spin-electromagnetic waves in ferrite-ferroelectric structures. An expression for transfer function of the OEO circuitry was derived. The theory enables one to calculate transmission characteristics and suppression of spurious harmonics of the multi-loop OEOs. The features of both magnetic and electric tunabilities are investigated.

Pseudospectral Maxwell solvers for an accurate modeling of Doppler harmonic generation on plasma mirrors with particle-in-cell codes.

With the advent of petawatt class lasers, the very large laser intensities attainable on target should enable the production of intense high-order Doppler harmonics from relativistic laser-plasma mirror interactions. At present, the modeling of these harmonics with particle-in-cell (PIC) codes is extremely challenging as it implies an accurate description of tens to hundreds of harmonic orders on a broad range of angles. In particular, we show here that due to the numerical dispersion of waves they induce in vacuum, standard finite difference time domain (FDTD) Maxwell solvers employed in most PIC codes can induce a spurious angular deviation of harmonic beams potentially degrading simulation results. This effect was extensively studied and a simple toy model based on the Snell-Descartes law was developed that allows us to finely predict the angular deviation of harmonics depending on the spatiotemporal resolution and the Maxwell solver used in the simulations. Our model demonstrates that the mitigation of this numerical artifact with FDTD solvers mandates very high spatiotemporal resolution preventing realistic three-dimensional (3D) simulations even on the largest computers available at the time of writing. We finally show that nondispersive pseudospectral analytical time domain solvers can considerably reduce the spatiotemporal resolution required to mitigate this spurious deviation and should enable in the near future 3D accurate modeling on supercomputers in a realistic time to solution.

Dispersion of electromagnetic waves in layered graphene-dielectric metamaterials

 In this paper possibility of creating a medium based on graphene-dielectric (quartz) structures with a hyperbolic shape of the dispersion relation is considered. Using the Bloch theorem and the transfer matrix method, dispersion relations are found for hyperbolic media, consisting of periodically located layers of graphene and a dielectric. The transfer matrix method gives the possibility to relate the amplitudes of the incident and reflected electromagnetic waves at the input to the layered structure with the amplitudes at the output by means of propagation and transfer matrixes. The frequency dependent optical conductivity of graphene sheet is calculated by Kubo formula which takes into account both interband and intraband transitions. It is shown that when the chemical potential of graphene is increased, the elliptic form of the dispersion curve turns into to hyperbolic. This result is due to the fact that the perpendicular component of the permittivity changes its sign when the chemical potential is changed.

Integrated modelling framework for short pulse high energy density physics experiments

Modelling experimental campaigns on the Orion laser at AWE, and developing a viable point-design for fast ignition (FI), calls for a multi-scale approach; a complete description of the problem would require an extensive range of physics which cannot realistically be included in a single code. For modelling the laser-plasma interaction (LPI) we need a fine mesh which can capture the dispersion of electromagnetic waves, and a kinetic model for each plasma species. In the dense material of the bulk target, away from the LPI region, collisional physics dominates. The transport of hot particles generated by the action of the laser is dependent on their slowing and stopping in the dense material and their need to draw a return current. These effects will heat the target, which in turn influences transport. On longer timescales, the hydrodynamic response of the target will begin to play a role as the pressure generated from isochoric heating begins to take effect. Recent effort at AWE [1] has focussed on the development of an integrated code suite based on: the particle in cell code EPOCH, to model LPI; the Monte-Carlo electron transport code THOR, to model the onward transport of hot electrons; and the radiation hydrodynamics code CORVUS, to model the hydrodynamic response of the target. We outline the methodology adopted, elucidate on the advantages of a robustly integrated code suite compared to a single code approach, demonstrate the integrated code suite's application to modelling the heating of buried layers on Orion, and assess the potential of such experiments for the validation of modelling capability in advance of more ambitious HEDP experiments, as a step towards a predictive modelling capability for FI.

Maximal Cherenkov γ-radiation on Fermi-surface of compact stars

The quantum magnetohydrodynamic model is employed in this paper to study the extraordinary (XO) elliptically polarized electromagnetic wave dispersion in quantum plasmas with spin-1/2 magnetization and relativistic degeneracy effects, considering also the electron-exchange and quantum diffraction of electrons. From the lower and upper calculated XO-modes, it is observed that, for electrons on the surface of the Fermi-sphere, the lower XO-mode can excite the Cherenkov radiation by crossing the Fermi-line, with some proper conditions depending on the values of independent plasma parameters, such as the relativistic-degeneracy, the atomic-number of constituent ions, and the magnetic field strength. Particularly, a lower electron number-density and Cherenkov radiation frequency limits are found to exist, for instance, for given values of the plasma ions atomic-number and the magnetic field strength below which the radiation can not be excited by the electrons on the Fermi-surface. This lower density limit increases by decrease in the atomic-number but decreases with decrease in the strength of the ambient magnetic field. It is remarkable that in this research it is discovered that the maximal Cherenkov-radiation per unit-length (the energy radiated by superluminal electrons traveling through the dielectric medium) coincides with the plasma number-densities, which is present in compact stars with the maximal radiation frequency lying in the gamma-ray spectrum. Current study can provide an important plasma diagnostic tool for a wide plasma density range, be it the solid density, the warm dense matter, the inertial confined or the astrophysical compact plasmas and may reveal an important cooling mechanism for white dwarfs. Current findings may also answer the fundamental astrophysical question on the mysterious origin of intense cosmic gamma-ray emissions.