TE Electromagnetic Waves Research Articles

On the Existence of Nonlinear Coupled Surface TE and Leaky TM Electromagnetic Waves in a Circular Cylindrical Waveguide

On the Existence of Nonlinear Coupled Surface TE and Leaky TM Electromagnetic Waves in a Circular Cylindrical Waveguide

Analyzing broadband tunable metamaterial absorbers by using the symmetry model

In this paper, a broadband tunable absorber based on bulk Dirac semimetal (BDS) in the far-infrared regime is studied. By optimizing the Femi energy and geometric size, the structure can achieve absorption levels greater than 90% in the 8.11-13.94 THz range, with a total thickness of 5.1 µm. Further, the bandwidth of this proposed absorber can be dynamically controlled by changing the Femi energy of the BDS instead of geometry. Meanwhile, the polarization and oblique incident angles in the TE and TM electromagnetic waves are also investigated. Finally, a new symmetry model is adopted to analyze the absorption mechanism, which is the innovation of this paper. This research result may provide potential applications for all types of optical photovoltaic devices and tunable biological chemistry sensors.

Nonlinear propagation of coupled surface TE and leaky TM electromagnetic waves

ABSTRACT Propagation of the coupled electromagnetic wave, which is a superposition of TE surface and TM leaky waves, in the Goubau line (a perfectly conducting cylinder covered by a concentric dielectric layer) filled with nonlinear inhomogeneous medium is studied (if the permittivity is linear, the coupled wave does not exist). Nonlinear coupled TE–TM wave is characterised by two (independent) frequencies and two (coupled) propagation constants (propagation constants). The physical problem is reduced to a nonlinear two-parameter transmission eigenvalue problem for Maxwell's equations. Existence of coupled TE–TM waves is proved. Intervals of localisation of propagation constants are found.

Constructing a partially transparent computational boundary for UPPE using leaky modes

In this paper, we introduce a method for creating a transparent computational boundary for the simulation of unidirectional propagation of optical beams and pulses using leaky modes. The key element of the method is the introduction of an artificial-index material outside a chosen computational domain and utilization of the quasi-normal modes associated with such artificial structure. The method is tested on the free space propagation of TE electromagnetic waves. By choosing the material to have appropriate optical properties, one can greatly reduce the reflection at the computational boundary. In contrast to the well-known approach based on a perfectly matched layer, our method is especially well suited for spectral propagators.

Design of metasurface polarization converter for near‐field application; stacked conical horn antenna for circular polarization

In this article, a three-layer transmission mode linear to circular polarization converter (TMCP) is proposed with low-level reflection coefficient and axial ratio (AR) at 9 GHz. Each layer of the proposed TMCP consists of microstrip patches and lines, providing inductive TM impedance and capacitive TE impedance on each layer to produce 90° out of phase between TE and TM electromagnetic waves. By removing the middle layer of the proposed metamaterial, a two-layer TMCP with low-level axial ratio at 8 GHz is obtained. However, the proposed two-layer TMCP suffers from disagreements between the reflection coefficients of the TE and TM modes, which produce fluctuations on the AR results in the near-field application. Low-level reflection coefficient and AR at 9 GHz achieved from the three-layer TMCP, indeed, make it efficient for the near-field of a horn antenna. Unit cells of the two-layer and three-layer TMCPs consisting patches and lines are simulated using periodic boundary conditions. In addition, the patches and lines are printed on a FR4 substrate and cut out in circle shapes. The three substrates are arranged at the determined separations and then installed in front of a profiled conical horn antenna. The measured AR of the antenna stacked by the three-layer TMCP is below 2 dB from 8.45 up to 9.6 GHz.

Anomalies in the reflection of an electromagnetic wave from the surface of a ferromagnet in a constant external electric field

Anomalies induced by an external electric field in the reflection of a TE electromagnetic plane wave, incident from without on the surface of a semi-infinite ferromagnetic insulator (in Voigt geometry), are studied. The effect these anomalies have on the magnitude and sign of the Goos–Hanchen effect for a beam of plane volume electromagnetic waves with s-type polarization, reflected from the surface of a ferromagnet, is investigated. The results are generalized to a one-dimensional ferromagnet–nonmagnet photonic crystal under the action of a constant electric field.

Properties of low frequency TE-electromagnetic wave in ternary plasma photonic crystal

Properties of low frequency TE-electromagnetic wave in ternary plasma photonic crystal

Визуализация плазмонов с помощью вектора Умова–Пойнтинга

We analyze the scattering of a plane TE electromagnetic wave of the visible range of wavelengths by a silver nano-cylinder with a concentric dielectric coating. The emerging plasmon resonances are treated using both the conventional presentation of the spatial distribution of the field amplitude nearby the object and by the spatial distribution of the Umov-Poynting vector. We demonstrate that application of the Umov-Poynting vector has obvious advantages: the standing and traveling waves are well resolved, simultaneously; the object interfaces become clearly visible in the spatial distribution. Unexpected impact is observed of the dielectric constant of the coating on the type of the plasmon resonance and the spatial field distribution.

Fano-like spectral profile in TE wave scattering by nanowire of dissipative and dispersive materials

We report the result of extending the study of Fano phenomena in the scattering of TE electromagnetic wave by nanowire having complex and dispersive permittivities, [Formula: see text], on the basis of exact Mie formulation. It is shown that the spectral profiles of scattering coefficients are sensitively affected by imaginary part of the permittivity and its overall frequency dependent properties. The cascaded resonance profile reported previously for real and positive permittivity is suppressed by a large [Formula: see text] while the spectral profile is broadened by the dispersive nature of [Formula: see text] as to increase the asymmetry of the profile. The negative sign of the real part of the permittivity, except for [Formula: see text], is generally found to eliminate the resonace profile. Further, the size (radius) of the nanowire is also shown to affect the resonance profile. Specific scattering coefficients calculated for silicon (Si) and silver (Ag) nanowire using experimental data of corresponding [Formula: see text] are demonstrated to exhibit the spectral profile for certain wire sizes with nicely fitted Fano profile.

Vector scattering from one dimensional periodic perfectly conducting surface: TE polarization

Based on the Rayleigh hypothesis and the Floquet's theorem, we propose a vector method for the problem of TE electromagnetic wave scattering by one-dimensional periodic conducting surface. The numerical results are consistent with the integral method and the T-matrix method in the particular case where the incidence plane is perpendicular to the row direction of the periodic surface. For the general case where the incidence plane is not perpendicular to the row direction of the surface, the proposed method obtains significant results which reveal cross-polarized and anisotropic characteristics in the scattering while the energy balance is kept satisfactory. This straight forward approach is much more efficient than the integral technique, thus suitable to be extended to other more involved periodic scattering problems.

Ultrahigh refractive index sensitivity of TE-polarized electromagnetic waves in graphene at the interface between two dielectric media

The behavior of the TE and TM electromagnetic waves in graphene at the interface between two semi-infinite dielectric media is studied. The dramatic influence on the TE waves propagation even at very small changes in the optical contrast between the two dielectric media is predicted. Frequencies of the TE waves are found to lie only in the window determined by the contrast. We consider this effect in connection with the design of graphene-based optical gas sensor. Near the frequency, where the imaginary part of the conductivity of graphene becomes zero, ultrahigh refractive index sensitivity and very low detection limit are revealed. The considered graphene-based optical gas sensor outperforms characteristics of modern volume refractive index sensors by several orders of magnitude.

Modeling of Interaction Layers from Conductive Microparticles with TE Electromagnetic Wave

Dependences of distribution, penetration, reflection and absorption of microwaves in the layers of conductive micro-particles on the frequency of the incident radiation and size of particles are obtained and investigated. Layers of conductive spherical particles as the shell, and without it are accepted in our work as the most common model of powder metals. So, this study allows to describe and classify features of electromagnetic wave heating of various metal powders and to predict the performance, in which it will be effective heating of metal powders by electromagnetic radiation.

Electron Dynamics in Presence of Static Helical Magnet Inside Circular Waveguide

The dynamics of an electron in the fields associated with a TE electromagnetic wave propagating inside a circular waveguide is analytically studied. The motion of this electron along the axis of the waveguide is investigated in the existence of a helical magnet (in which the field is perpendicular to the axis of the waveguide and rotating as a function of position along the magnet). It is shown that it can be accelerated due to its interaction with polarized fields of microwave radiation propagating along the waveguide. The fields for the lowest order TE11 modes and the deflection angle of electron trajectory, due to these fields, are obtained. Also, an expression of the acceleration gradient of the electron and its energy gain are evaluated for different intensities and frequencies of the microwave.

Angular electromagnetic response of double-ring metamaterials for TE polarization

We investigate transmission characteristics in symmetric planar double-ring metamaterials at oblique angles of incidence theoretically. The double-ring microwave metamaterials are used to study resonant response to incident TE electromagnetic wave. The trapped-mode resonant feature results from the excitation of antisymmetric current mode and the quality factor is associated to the angle of incidence.

Reflection, absorption and transmission of TE electromagnetic waves propagation in a nonuniform plasma slab

A numerical scheme is described to compute the reflection, absorption, and transmission coefficients of TE m , 0 and plane electromagnetic waves propagating in a nonuniform plasma slab. The numerical solutions are in good agreement with theoretical solutions for two different kinds of electron density profiles. The solutions for various electron density profiles will be shown in TE m , 0 mode. The method has applications to predicting the fields in plasmas where the density is profile is known, such as in microwave breakdown in a waveguide.

Coherent Reflection of Electromagnetic Plane Waves from Infinite Rough Slabs

We adopt the prospect of an observer interested to optimise the signal-to-noise ratio in the reception of the backward radiation coming from a surface illuminated by an electromagnetic wave with a wavelength chosen to minimize the diffuse scattering so that he has just to point his receiver in the direction of the coherent reflection. Then, to analyse the coherent reflection for harmonic plane waves impinging on a dielectric infinite film deposited on a metallic substrate we develop a formalism generalizing the customary angular spectrum representation used to tackle this kind of problem. This new approach whose efficiency is proved in the easier situation of a dielectric film endowed with an impedance, is used to get the coherent reflection from a structured 1D-dielectric film illuminated by TE and TM electromagnetic plane waves when the rough amplitude h is small enough to justify 0(h 2) approximations. The Idemen technique is used to get the boundary conditions needed to tackle these scattering problems.

Grazing angle scattering of electromagnetic waves in gratings with varying mean parameters

Highly unusual sensitivity of wave scattering in thick periodic gratings to small step-like variations of mean structural parameters at the grating boundaries is predicted and described for the case when the scattered wave (the +1 diffracted order) propagates almost parallel to the front grating boundary (the geometry of GAS — grazing-angle scattering). The analysis is carried out for GAS of bulk TE electromagnetic waves in holographic gratings with varying mean permittivity, and GAS of optical modes guided by a slab with a periodic groove array and varying mean thickness. In particular, it is shown that variations of the mean permittivity by ∼0.007% may result in several times variations in the scattered wave amplitude in the grating. At the same time, it is also demonstrated that near the main GAS resonance, the scattered wave amplitudes are only weakly dependent on small variations of mean structural parameters. Physical explanations of the predicted effects are presented. Possible ways of enhancing and, vice versa, reducing (compensating for) the unusual sensitivity of GAS are indicated. Feasible applications of the predicted effects for the design of new highly sensitive sensors and measurement techniques are discussed.

Frequency response of second-order extremely asymmetrical scattering in wide uniform holographic gratings

Second-order extremely asymmetrical scattering (EAS) and grazing-angle scattering (GAS) are types of Bragg scattering in slanted wide periodic gratings. They occur when the second diffracted order satisfies the Bragg condition and has a wavevector parallel (for EAS) and almost parallel (for GAS) to the grating boundaries. In this paper, for the first time, a rigorous numerical study of the frequency responses of second-order EAS and GAS is presented for bulk TE electromagnetic waves in planar holographic gratings. A highly unusual pattern of strong optical resonances in the side-lobe structure of these frequency responses is predicted. A relationship between these resonances and the previously predicted GAS resonances (at zero detunings of the Bragg condition) is established and analysed. A special new type of eigenmodes in slanted wide periodic gratings with strong frequency detunings are predicted in the case of second-order EAS and GAS. The eigenmodes are shown to be guided by the grating alone without any conventional guiding effect in the structure. The typical field structure in such eigenmodes is investigated and discussed.

Rigorous analysis of grazing-angle scattering of electromagnetic waves in periodic gratings

Grazing-angle scattering (GAS) is a type of Bragg scattering of waves in slanted non-uniform periodic gratings, when the diffracted order satisfying the Bragg condition propagates at a grazing angle with respect to the boundaries of a slab-like grating. Rigorous analysis of GAS of bulk TE electromagnetic waves is undertaken in holographic gratings by means of the enhanced T-matrix algorithm. A comparison of the rigorous and the previously developed approximate theories of GAS is carried out. A complex pattern of numerous previously unknown resonances is discovered and analysed in detail for gratings with large amplitude, for which the approximate theory fails. These resonances are associated not only with the geometry of GAS, but are also typical for wide transmitting gratings. Their dependence on grating amplitude, angles of incidence and scattering, and grating width is investigated numerically. Physical interpretation of the predicted resonances is linked to the existence and the resonant generation of special new eigenmodes of slanted gratings. Main properties of these modes and their field structure are discussed.

Non-steady-state double-resonant extremely asymmetrical scattering of waves in periodic gratings

Double-resonant extremely asymmetrical scattering (DEAS) is a strongly resonant type of Bragg scattering in two joint or separated uniform gratings with different phases. It is characterised by a very strong increase of the scattered and incident wave amplitudes inside and between the gratings at a resonant phase shift between the gratings. DEAS is realised when the first diffracted order satisfying the Bragg condition propagates parallel to the grating boundaries, and the joint or separated gratings interact by means of the diffractional divergence of the scattered waves from one grating into another. This Letter develops a theory of non-steady-state DEAS of bulk TE electromagnetic waves in holographic gratings, and investigates the process of relaxation of the incident and scattered wave amplitudes to their steady-state values inside and outside the gratings. Typical relaxation times are determined. Physical explanation of the predicted effects is presented.