Slow Electromagnetic Waves Research Articles

SLOW ELECTROMAGNETIC WAVES IN PLANAR THREE-COMPONENT WAVEGUIDE STRUCTURE WITH MU-NEGATIVE METAMATERIAL

This work is devoted to study of the dispersive properties of the slow electromagnetic waves that propagate along the planar waveguide structure that consists of semi-bounded plasma region, metamaterial slab and semibounded region of ordinary dielectric. It is studied the case when all media are homogeneous and isotropic. The dispersion properties, the phase and group velocities, as well as the electromagnetic field spatial structure of the eigen TE modes are studied in the frequency range where the metamaterial possess negative permeability.

Slow Surface Eigenmodes Directed by the Mu-Negative Metamaterial Slab

The paper presents the results of the study of slow surface electromagnetic waves directed along the flat mu-negative metamaterial slab surrounded by ordinary dielectric material. It is considered the case of isotropic and homogeneous metamaterial without losses. This metamaterial possesses the positive permittivity and the negative permeability over a definite frequency band. It is found that two surface modes of TE polarization can propagate along such waveguide structure. The dispersion properties, the spatial distribution of the electromagnetic field, as well as the phase and group velocities of these slow modes are studied. The first mode is a conventional forward wave, and has a lower frequency and lower phase velocity than the second mode. The second mode may have zero group velocity at a certain frequency. Characteristics of these surface modes for different values of the mu-negative slab parameters have been studied. The studied surface electromagnetic waves can be used for practical applications as in laboratory experiments, as in various technologies.

Slow Electromagnetic Waves in Double-Layer Cylindrical Waveguide Filled With Right- and Left-handed Media

Slow Electromagnetic Waves in Double-Layer Cylindrical Waveguide Filled With Right- and Left-handed Media

The slow electromagnetic wave effect induced by the interaction of dark and quasi-dark modes in microwave metamaterials

The slow electromagnetic wave effect induced by the interaction of dark and quasi-dark modes in microwave metamaterials

Improving homogeneity in abdominal imaging at 3 T with light, flexible, and compact metasurface.

Radiofrequency field inhomogeneity is a significant issue in imaging large fields of view in high- and ultrahigh-field MRI. Passive shimming with coupled coils or dielectric pads is the most common approach at 3 T. We introduce and test light and compact metasurface, providing the same homogeneity improvement in clinical abdominal imaging at 3 T as a conventional dielectric pad. The metasurface comprising a periodic structure of copper strips and parallel-plate capacitive elements printed on a flexible polyimide substrate supports propagation of slow electromagnetic waves similar to a high-permittivity slab. We compare the metasurface operating inside a transmit body birdcage coil to the state-of-the-art pad by numerical simulations and in vivo study on healthy volunteers. Numerical simulations with different body models show that the local minimum of causing a dark void in the abdominal domain is removed by the metasurface with comparable resulting homogeneity as for the pad with decreasing maximum and whole-body SAR values. In vivo results confirm similar homogeneity improvement and demonstrate the stability to body mass index. The light, flexible, and inexpensive metasurface can replace a relatively heavy and expensive pad based on the aqueous suspension of barium titanate in abdominal imaging at 3 T.

Контроль электрофизических параметров метаматериалов методом поверхностных электромагнитных волн

Development of metamaterials has led to the search and choice of effective methods of radio-wave nondestructive testing of their electrophysical parameters. The existing approaches to testing based on extracted of effective electrophysical parameters of metamaterials from the coefficients of reflection and transmission of an electromagnetic wave have low reliability and don't provide their local control. We present the new radio-wave method of local control of complex dielectric permittivity and magnetic permeability, as well as the thickness of metamaterial plate on a metal substrate with surface microwaves. The method is based on the solution of inverse problem in the determination of effective electrophysical parameters of metamaterial from the frequency dependence of the attenuation coefficient of the field of a slow surface electromagnetic wave excited in a test sample. The electrophysical parameters of the metamaterial are represented as parametric frequency functions in accordance with the Drude-Lorentz models of dispersion, and the solution of the inverse problem is reduced to minimizing the objective function constructed based on the discrepancy between the experimental and design theoretical values of the attenuation coefficients of surface electromagnetic wave fields on a grid of discrete frequencies. The structure of a measuring complex that implements the proposed method of control is proposed. For the numerical and experimental verification of the method, a sample of a metamaterial plate based on SRR elements with a negative refraction region in the frequency band 10.06–10.64 GHz was investigated. Experimental investigations of the metamaterial demonstrated the theoretical capabilities gained with measurement of the local electrophysical parameters with relative error not greater 10 %.

Спектри власних хвиль плазмового твердотільного циліндра в сильному поздовжньому магнітному полі

Subject and Purpose. Eigenwave studies of various bounded structures make a prolific line of investigation in both modern radiophysics and solid-state and functional electronics. Conducting solids demonstrating plasma (semiconductor) properties attract particular attention. Owing to the high conductivity of semiconductors (as it is inversely proportional to the charge carrier effective mass that is smaller than the free electron mass), interest exists in propagation features of slow elliptical-polarization electromagnetic waves – helicons – in magnetized semiconductor waveguides. The present work aims to determine eigenwave spectra of a solid-state plasma cylinder in a strong constant concentric magnetic field. Methods and Methodology. The eigenwave theoretical study of a magnetoplasma cylinder in the free space is conducted in terms of Maxwell's equations. The motion equation of conduction electrons of a solid-state plasma is adopted with quasi-stationarity electromagnetic field conditions satisfied. The collision frequency of majority charge carriers is assumed substantially less than their cyclotron frequency. Results. The dispersion equation of a cylindrical solid-state plasma (semiconductor) waveguide has been obtained. It has been shown that a collisionless magnetoplasma waveguide supports propagation of bulk and surface helicons. The propagation is accompanied by the surface current flowing lengthways cylinder components. Charged particle collisions destroy the surface current and initiate additional (to helicons) H-type hybrid waves such that their phase velocities coincide with phase velocities of the helicons. It has been found that the nonreciprocity effect holds for the waveguide eigenwaves having identical field distribution structures but different azimuthal propagation directions, and it also does as soon as the external magnetic field changes its sense. Conclusion. The research results have deepened our understanding of physical properties of bounded structures with plasma-like filling media. More systematization has been added to the knowledge of eigenwave behavior of these structures in a quasi-stationarity electromagnetic field.

SLOW SURFACE ELECTROMAGNETIC WAVES AT THE METASURFACE / DISSIPATIVE DIELECTRIC INTERFACE

The possibilities of the slow surface electromagnetic waves propagation along the flat boundary of a metasurface with a dissipative dielectric are studied. The metasurface is a thin flat slab of metamaterial with simultaneously negative permittivity and permeability with "amplification". All media were assumed to be isotropic. Dispersion dependences are obtained for the eigenmodes of such a waveguide structure. The possibility of full compensation of the energy losses of surface waves by the appropriate choice of the “gains” values is demonstrated.

Slow Electromagnetic Waves in a Left-Handed Medium Based on Magnetoactive Plasma Metamaterial

The spectrum of slow electromagnetic waves (EMWs) existing in a left-handed medium based on a magnetoactive plasma metamaterial has been theoretically studied. The metamaterial under study is a strip waveguide completely filled with longitudinally magnetized cold electron plasma containing a periodic structure made from ideally conducting split-ring resonators. It is shown that there exists either one (ordinary) or two (ordinary and extraordinary) slow EMWs in a left-handed medium based on anisotropic plasma, depending on the chosen values of the split-ring resonator eigenfrequency and magnetic induction. It is found that the extraordinary EMW has a negative dispersion, while the dispersion characteristic of the ordinary EMW contains portions of both negative and positive dispersion.

Evaluating the Accuracy of Reconstruction of the Electrical and Geometric Parameters of Multilayer Dielectric Coatings by a Multifrequency Radio-Wave Method for Slow Surface Electromagnetic Waves

One of the most important problems in the diagnostics of multilayer dielectric materials and coatings is the development of methods for quantitative interpretation of the results of monitoring the electrical and geometric parameters of these materials. Results are presented from a study of the potential informativeness of a multifrequency radio-wave method for slow surface electromagnetic waves for reconstruction of the electrical and geometric parameters of multilayer dielectric coatings. A simulation model is shown for evaluating the accuracy of reconstructing the electrical and geometric parameters of multilayer dielectric coatings. The model takes into account the electrical and geometric parameters of the coating, the level of noise in the measurement data, and the measurement bandwidth. Simulation modeling and experimental test data for the reconstruction of the relative dielectric constants and thicknesses of one- and two-layer equal-thickness dielectric coatings based on polymethyl methacrylate, ftoroplast (teflon) F-4D, and RO3010 for different values of the mean square deviation of the noise level in the measured attenuation coefficients for the field of a slow surface electromagnetic wave. The accuracy of the reconstruction of the geometric and electrical parameters of the layers is found to decrease as the number of estimated parameters and the noise level increase, as well as when the dielectric constant and thickness of the layers are reduced. Experimental data confirm the adequacy of the simulation model developed here. This model can be used for a specific measurement complex employing a multifrequency radio-wave technique for slow surface electromagnetic waves to estimate quantitatively the potential possible accuracy of reconstructing the geometric and electrical parameters of multilayer dielectric materials and coatings. A simulation model and experimental study of a multilayer dielectric coating show that for a measurement bandwidth of 1 GHz the errors in estimating the dielectric constants and thicknesses of the layers do not exceed 10% with a confidence coefficient of 0.95 for a mean square deviation of 0.003–0.004 in the noise level.

Surface Plasmonic Feature Microwave Sensor With Highly Confined Fields for Aqueous-Glucose and Blood-Glucose Measurements

This article proposes a method of using a highly efficient spoof surface plasmon polariton (SSPP) endfire sensor for monitoring of aqueous glucose solutions and on-body glucose measurements. Occupying an area of around (52 mm $\times24$ mm), the proposed sensor radiates an endfire beam into a glucose water solution with a substantially reduced effective aperture. At the coplanar waveguide (CPW) port of the sensor, a pair of triangular ground planes was added to suppress the sidelobes, which have been proven to be counter-productive in glucose sensing. The slow-wave nature of the proposed SSPP endfire sensor has further advantageously enabled the glucose concentrations to be measured with an increased sensitivity. The guiding body of the sensor was designed to simulate an electromagnetic beam propagating in a dense dielectric medium with a group velocity comparable to the phase velocity of light propagating in a glucose solution. Consistent with the results of our analysis, the experimental results of this work revealed that the gradual transition of slow electromagnetic wave from the SSPP endfire sensor to the glucose water solution has successfully enabled the glucose concentrations of a solution to be measured and displayed in the form of highly observable resonant frequency shifts in S 11 parameters. The proposed design has achieved a high sensitivity of 150 MHz/mgmL−1 during on-body measurements.

Control of defects in the multilayer dielectric materials and coatings in the microwave range

The development of modern engineering is inextricably linked with the development of the new types of multilayer dielectric materials. Existing radio wave methods for monitoring interlayer defects in such materials exhibit low accuracy in reconstructing the geometric parameters of defects. The results of studying extended interlayer defects in the three-layer coating consisting of polymethyl methacrylate, F-4D PTFE, and semi-hard rubber by the method of surface electromagnetic waves are presented. The method is based on the solution of inverse problems in the reconstruction of the geometric parameters of extended interlayer defects of special multilayer materials and coatings from the frequency dependence of the attenuation coefficient of the field of a slow surface electromagnetic wave. Unlike the methods that make use from the complex reflection coefficient we proposed to increase the accuracy of the reconstruction of the geometric parameters of extended interlayer defects taking into account the linear frequency dependence of the attenuation coefficient as well as reducing the number of fixed measurement frequencies. Moreover, the determination procedure is rather simple, since only the field strength of the surface electromagnetic wave is measured, and there is no need for phase measurements. Experimental data obtained on a multifrequency measuring complex in the range of 10 – 11 GHz were used for reconstruction of the interlayer defects in the coating under study. The developed method provided a relative error of thickness estimation below 10%. The proposed method approach can be used in studying multilayer dielectric coatings on the metal for detection of delamination in the lack of glue or poor adhesion between the layers. The developed method is also suitable for control of the defects in semiconductors, ferrite and composite materials.

Evaluation of the accuracy of reconstruction of the electrophysical and geometric parameters of multilayer dielectric coatings by the multi-frequency radio wave method of a slow surface electromagnetic waves

One of the most important diagnostic problems multilayer dielectric materials and coatings is the development of methods for quantitative interpretation of the checkout results their electrophysical and geometric parameters. The results of a study of the potential informativeness of the multi-frequency radio wave method of surface electromagnetic waves during reconstruction of the electrophysical and geometric parameters of multilayer dielectric coatings are presented. The simulation model is presented that makes it possible to evaluate of the accuracy of reconstruction of the electrophysical and geometric parameters of multilayer dielectric coatings. The model takes into account the values of the electrophysical and geometric parameters of the coating, the noise level in the measurement data and the measurement bandwidth. The results of simulation and experimental investigations of reconstruction of the structure of relative permittivitties and thicknesses of single-layer and double-layer dielectric coatings with different thicknesses, with different values of the standard deviation (RMS) of the noise level in the measured attenuation coefficients of the surface slow electromagnetic wave are presented. Coatings based on the following materials were investigated: polymethyl methacrylate, F-4D PTFE, RO3010. The accuracy of reconstruction of the electrophysical parameters of the layers decreases with an increase in the number of evaluated parameters and an increase in the noise level. The accuracy of the estimates of the electrophysical parameters of the layers also decreases with a decrease in their relative permittivity and thickness. The results of experimental studies confirm the adequacy of the developed simulation model. The presented model allows for a specific measuring complex that implements the multi-frequency radio wave method of surface electromagnetic waves, to quantify the potential possibilities for the accuracy of reconstruction of the electrophysical and geometric parameters of multilayer dielectric materials and coatings. Experimental investigations and simulation results of a multilayer dielectric coating demonstrated the theoretical capabilities gained relative error permittivity and thickness of the individual layers with relative error not greater than 10 %, with a measurement bandwidth of 1 GHz and RMS of noise level 0,003–0,004.

Медленные электромагнитные волны в левой среде на основе магнитоактивного плазменного метаматериала

The paper presents the theoretical study results of the control of the spectrum of slow electromagnetic waves (EMWs) existing in a “left-handed” medium based on a magnetically active plasma metamaterial. The investigated metamaterial is a strip waveguide completely filled with a longitudinally magnetized “cold” electron plasma, containing a periodic structure of perfectly conducting split-ring resonators (SRRs). It is shown that either one (ordinary), either two (ordinary and unordinary) slow EMWs can exist in a “left-handed” medium based on the magnetically active plasma and the spectrum of these waves depends on the SRR own frequency and magnetic induction. The unordinary slow EMW possesses by the negative dispersion and the dispersion characteristic of the ordinary EMW has the sections with both the negative and positive dispersions.

Fast and Slow Electromagnetic Waves in a Longitudinally Magnetized Thin-Film Ferromagnetic Metamaterial

We present the results of a theoretical study of the electrodynamic characteristics of fast and slow electromagnetic waves (EMWs) propagating in a metamaterial consisting of a ferromagnetic film inside which there is a periodic lattice of thin metal wires. The ferromagnetic thin-film metamaterial possesses the properties of a left-handed medium at frequencies of slow electromagnetic waves. In a ferromagnetic metamaterial, in comparison with a conventional ferromagnetic film, the cutoff frequencies of fast and slow electromagnetic waves shift to a higher frequency range and the electromagnetic waves themselves become very slow.

Reconstruction of The Structure of the Electrophysical Parameters of Multilayer Dielectric Materials and Coatings from The Frequency Dependence of the Attenuation Coefficient of the Field of a Surface Electromagnetic Wave

A new radio-wave method of reconstruction of the relative permittivities and thicknesses of multilayer materials and coatings is proposed. The method is based on the solution of inverse problems in the reconstructionof the structure of the electrophysical parameters of special multilayer materials and coatings from the frequency dependence of the attenuation coefficient of the field of a slow surface electromagnetic wave. The principal differences of the new method from well-known radio wave methods of determining the electrophysical parameters of multilayer materials are demonstrated. In contrast to methods that involve an informative parameter – the complex reflection coefficient – the proposed method yields an increase in the precision and reliability of the reconstruction of the structure of the relative permittivitties and thicknesses. Improved precision and reliability is achieved by taking into account the linear dependence of the attenuation coefficient on frequency as well as reducing the number of fixed measurement frequencies. The results of experimental studies that confirm the linear dependence of the attenuation coefficient of the field of a surface electromagnetic wave on frequency as well as a decrease in the number of fixed measurement frequencies are presented. The method implements a simple measurement procedure, since only the values of the field strength of the surface electromagnetic wave are measured and there is no need for phase measurements in the method. Reconstruction of the permittivity of a three-layer coating consisting of polymethyl methacrylate, F-4D PTFE, and semi-hard rubber with precision acceptable for practical applications is realized with the use of experimental results of measurements in a multifrequency measurement complex in the range 9–10 GHz by means of the new method. Experimental investigations of a multilayer dielectric coating demonstrated the theoretical capabilities gained with measurement of the relative permittivity and thickness of the individual layers with relative error not greater than 8 and 6%, respectively.

Быстрые и медленные электромагнитные волны в продольно намагниченном тонкопленочном ферромагнитном метаматериале

The results of a theoretical study of the electrodynamic characteristics of fast and slow electromagnetic waves (EMWs) propagating in a metamaterial are presented. The metamaterial consists of a ferromagnetic film inside which a periodic lattice of thin metal wires is located. It has been established that the ferromagnetic thin-film metamaterial possesses the properties of a left-handed medium at frequencies of slow electromagnetic waves. It is shown that, in a ferromagnetic metamaterial, compared with a conventional ferromagnetic film, the cutoff frequencies of fast and slow EMWs shift to a higher frequency range, and EMWs themselves become strongly slowed waves.

Generation of Slow Surface Plasmon Polaritons in a Complex Waveguide Structure with Electric Current Pump

AbstractA planar spaser structure composed of semiconducting film and graphene with DC current is proposed and theoretically explored. Graphene possesses velocity of drift current carriers comparable with the phase velocity of surface plasmon polaritons (SPPs) in ultrathin semiconducting film at the terahertz regime. When the synchronism condition between current and slow surface electromagnetic waves is realized, the amplification of plasmons by electric current takes place. In the proposed complex waveguide structure, positive feedback is realized due to reflections from the edges of the active waveguide, and the SPPs are decoupled into light by a microscopic grating manufactured on the semiconducting film surface.

SURFACE ELECTROMAGNETIC WAVES IN A GAP BETWEEN TWO LEFT-HANDED MATERIALS

The slow surface electromagnetic waves that propagate along the planar waveguide structure that contains two identical isotropic left-handed material with the vacuum (or air) gap has been considered. The possibility of propagation of slow surface electromagnetic waves of TM and TE polarizations in the frequency range at which the dielectric permittivity and magnetic permeability are negative are shown. By selecting a frequency, one, two or three modes can be excited simultaneously. The group and phase velocities of the TE polarization waves are directed in opposite directions. The frequency range of the existence of the TE mode with an antisymmetric field distribution lies above the frequency range of the existence of the TE mode with a symmetric field distribution. The TM wave, depending on the wavelength, can be either forward or backward, or have zero group velocity. The wave of TM-polarization has a slightly varying group velocity in a sufficiently wide frequency range. A rich set of different properties of these waves make them promising in applications.

Finite magneto-static field effect on the excitation of THz hybrid modes in an elliptical metallic plasma waveguide with two energy sources

The effect of finite magnetic field on the excitation, generation, and amplification of slow electromagnetic waves at THz frequency in a magnetized plasma waveguide with elliptical cross section is investigated. In configuration mentioned above, there are two electron beams with opposite directions as energy sources, and the role of magnetic field power on the appearance of the number of dispersion branches is analysed. It is shown that with increasing magnetic field, the field profiles of hybrid waves are increased in regions where the interaction of waves and electron beams are optimized. It is also shown that by applying the magnetic field, generation of THz frequencies can be easy to obtain in comparison to the unmagnetized case. In other words, by applying a finite magnetic field, better THz excitation occurs in the absence of high accelerating voltage. Increasing growth rate which can be achieved with increasing static magnetic field is also investigated. In this paper, because of high longitudinal velocity of electron beams, the effect of finite magnetic field on the fluctuations of electron beams is considered negligible.