Field Of Electromagnetic Wave Research Articles

The dependence of the conductivity tensor on electromagnetic waves and laser fields in a quantum well with infinite potential in the case of electrons - optical phonon scattering

There are many studies on low-dimensional semiconductors, including quantum wells. Conductivity tensor is one of the key concepts in materials research. This work studies the dependence of the conductivity tensor on electromagnetic waves and laser fields in a quantum well with infinite potential in the case of electrons - optical phonon scattering. Results are obtained using the quantum kinetic equation for electrons in a quantum well, the particle system is placed in an electromagnetic wave field and a laser field, from solving the quantum kinetic equation yields conductivity tensor expressions.This work also only considers the case of electron scattering - optical phonon and with quantum well there can be infinite potential. The conductivity tensor expression shows its dependence on the electromagnetic wave frequency, laser field frequency, laser field amplitude, and other parameters that characterize the quantum well.A graph of the dependence of the conductivity tensor on electromagnetic wave frequency, laser field frequency, and laser field amplitude will be plotted and examined. The semiconductor investigated here is the GaAs/GaAsAl quantum well.

The influence of electromagnetic waves on conductivity tensor in the presence of laser field in quantum wells with parabolic potential for the case of electrons-acoustic phononscattering

In quantum well studies, the conductivity tensor problem is one of the fundamental problems. In this work the topic covered here is the effect of electromagnetic waves on the conductivity tensor with the presence of a laser field in a quantum well with a parabolic potential considering the case ofelectrons-acoustic phonon scattering. By using quantum kinetic equations for electrons in quantum wells with parabolic potential, the author has calculated conductivity tensor with electrons–acoustic phonon scattering in the presence of an electromagnetic wave field and a laser field. The expression tensor for conductivity shows its dependence on the frequency of the electromagnetic wave field, the frequency of the laser field, and other parameters specific to the system. From the conductivity tensor expression plotted the effect of the electromagnetic wave field on the conductivity tensor in the presence of the laser field. The quantum well is discussed and plotted here is the GaAs/GaAsAl quantum well.

A Review on Metasurface: From Principle to Smart Metadevices

Metamaterials are composed of periodic subwavelength metallic/dielectric structures that resonantly couple to the electric and magnetic fields of the incident electromagnetic waves, exhibiting unprecedented properties which are most typical within the context of the electromagnetic domain. However, the practical application of metamaterials is found challenging due to the high losses, strong dispersion associated with the resonant responses, and the difficulty in the fabrication of nanoscale 3D structures. The optical metasurface is termed as 2D metamaterials that inherent all of the properties of metamaterials and also provide a solution to the limitation of the conventional metamaterials. Over the past few years, metasurfaces; have been employed for the design and fabrication of optical elements and systems with abilities that surpass the performance of conventional diffractive optical elements. Metasurfaces can be fabricated using standard lithography and nanoimprinting methods, which is easier campared to the fabrication of the counterpart 3 days metamaterials. In this review article, the progress of the research on metasurfaces is illustrated. Concepts of anomalous reflection and refraction, applications of metasurfaces with the Pancharatanm-Berry Phase, and Huygens metasurface are discussed. The development of soft metasurface opens up a new dimension of application zone in conformal or wearable photonics. The progress of soft metasurface has also been discussed in this review. Meta-devices that are being developed with the principle of the shaping of wavefronts are elucidated in this review. Furthermore, it has been established that properties of novel optical metasurface can be modulated by the change in mechanical, electrical, or optical stimuli which leads to the development of dynamic metasurface. Research thrusts over the area of tunable metasurface has been reviewed in this article. Over the recent year, it has been found that optical fibers and metasurface are coagulated for the development of optical devices with the advantages of both domains. The metasurface with lab-on fiber-based devices is being discussed in this review paper. Finally, research trends, challenges, and future scope of the work are summarized in the conclusion part of the article.‬‬‬‬‬‬‬

Electric Dipole Active Magnetic Resonance and Nonreciprocal Directional Dichroism in Magnetoelectric Multiferroic Materials in Terahertz and Millimeter Wave Regions

We review electric dipole active magnetic resonance and nonreciprocal directional dichroism in magnetoelectric multiferroic materials in terahertz and millimeter wave regions. Owing to dynamical magnetoelectric coupling generated by the spin-dependent electric polarization, magnetic resonance, which usually occurs owing to magnetic dipole transition, can be induced by the oscillating electric fields of electromagnetic wave. This electric dipole active magnetic resonance can be useful for microscopic investigations of magnetic excitation in unconventional spin systems. The magnetoelectric coupling also induces the nonreciprocal directional dichroism, which provides a novel functionality to materials as an optical diode, in teraheltz and microwave absorption by magnetic resonance. As examples, we describe the results of the high field ESR measurements of the triangular lattice antiferromagnet $$\hbox {CuFeO}_{\mathrm{2}}$$ and the interacting quantum spin dimer systems $$\hbox {TlCuCl}_{\mathrm{3}}$$ and $$\hbox {KCuCl}_{\mathrm{3}}$$ .

Semi-analytical solutions of seismo-electromagnetic signals arising from the motional induction in 3-D multi-layered media: part I\u2014theoretical formulations

Taking into account the motional induction effect, in which the Earth crust that has finite electrical conductivity vibrates in the ambient geomagnetic field resulting in motionally induced electric current, we derive semi-analytical solutions of seismo-electromagnetic signals generated by an earthquake source in 3-D multi-layered media, which consists of an air half-space and multiple solid layers. First, both the elastic and electromagnetic (EM) wave-fields involved in the governing equations, which have the form of Maxwell’s equations coupled with elastodynamic equations, are expanded by a set of vector basis functions in cylindrical coordinate system. Then, we reorganize the transformed governing equations expressed by expansion coefficients and obtain corresponding first-order ordinary differential equations for the wave-fields in air and solid media. The expansion of the motionally induced electric current and the reorganization of Maxwell’s equations are the most important part, and also the most complicated and tedious part of this work. Thereafter, we solve the first-order ordinary differential equations through the Luco–Apsel–Chen generalized reflection and transmission method gaining solutions of the expansion coefficients. Finally, we obtain the frequency–space-domain semi-analytical solutions written as integrations of corresponding expansion coefficients over wavenumber domain, which can be numerically calculated by the discrete wavenumber method. The time-domain solutions can be achieved by further applying the discrete inverse Fourier transform. To have a numerical stability at any high frequency, we adopt the analytical regularization approach in the derivation process by introducing two artificial interfaces with infinitely small distance from the source. On the basis of the semi-analytical solutions, we can tell that only EM fields of TM mode (in which magnetic fields are transversely polarized) will be induced by SH waves, whereas EM fields of both TE mode (in which magnetic fields are transversely polarized) and TM mode will be induced by P and SV waves. The derived semi-analytical solutions can be used to calculate seismo-electromagnetic signals either below or above the free surface.

Characterising Exciton Generation in Bulk-Heterojunction Organic Solar Cells.

In this paper, characterisation of exciton generation is carried out in three bulk-heterojunction organic solar cells (BHJ OSCs)—OSC1: an inverted non-fullerene (NF) BHJ OSC; OSC2: a conventional NF BHJ OSC; and OSC3: a conventional fullerene BHJ OSC. It is found that the overlap of the regions of strong constructive interference of incident and reflected electric fields of electromagnetic waves and those of high photon absorption within the active layer depends on the active layer thickness. An optimal thickness of the active layer can thus be obtained at which this overlap is maximum. We have simulated the rates of total exciton generation and position dependent exciton generation within the active layer as a function of the thicknesses of all the layers in all three OSCs and optimised their structures. Based on our simulated results, the inverted NF BHJ OSC1 is found to have better short circuit current density which may lead to better photovoltaic performance than the other two. It is expected that the results of this paper may provide guidance in fabricating highly efficient and cost effective BHJ OSCs.

Nonlinear acoustic metamaterial for efficient frequency down-conversion.

Frequency conversion is one of the most important nonlinear wave phenomena that has been widely used in the field of electromagnetic waves for changing signal frequencies. Recently, studies on frequency conversion have been actively performed in the field of acoustics owing to its importance in nonlinear ultrasonic nondestructive evaluation and directional speakers. However, acoustic frequency conversion presents relatively poor efficiency owing to the small amplitudes of the converted frequencies and undesired intermodulation. Herein, we propose an acoustic metamaterial to achieve an efficient frequency down-conversion of acoustic waves. Based on background theory, we discovered that the amplitudes of the converted frequencies are inversely proportional to the cube of the speed of sound. Accordingly, we amplify the converted frequency components by reducing the effective speed of sound by coiling up space while suppressing undesired intermodulation by the Bragg gap. Numerical simulation and analytical results show that efficient frequency down-conversion is possible using the corresponding metamaterial. Additionally, dissipation due to viscosity and boundary layer effects is considered. We expect our study results to facilitate research regarding acoustic frequency conversion.

Adiabatic mode transformation in width-graded nano-gratings enabling multiwavelength light localization

We delineate the four principal surface plasmon polariton coupling and interaction mechanisms in subwavelength gratings, and demonstrate their significant roles in shaping the optical response of plasmonic gratings. Within the framework of width-graded metal–insulator-metal nano-gratings, electromagnetic field confinement and wave guiding result in multiwavelength light localization provided conditions of adiabatic mode transformation are satisfied. The field is enhanced further through fine tuning of the groove-width (w), groove-depth (L) and groove-to-groove-separation (d). By juxtaposing the resonance modes of width-graded and non-graded gratings and defining the adiabaticity condition, we demonstrate the criticality of w and d in achieving adiabatic mode transformation among the grooves. We observe that the resonant wavelength of a graded grating corresponds to the properties of a single groove when the grooves are adiabatically coupled. We show that L plays an important function in defining the span of localized wavelengths. Specifically, we show that multiwavelength resonant modes with intensity enhancement exceeding three orders of magnitude are possible with w < 30 nm and 300 nm < d < 900 nm for a range of fixed values of L. This study presents a novel paradigm of deep-subwavelength adiabatically-coupled width-graded gratings—illustrating its versatility in design, hence its viability for applications ranging from surface enhanced Raman spectroscopy to multispectral imaging.

A new approach to the economic synthesis of multi-walled carbon nanotubes using a Ni/MgO catalyst

The present paper describes the efficiency of the synthesis of multi-walled carbon nanotubes (MWCNTs), which is achieved through the implementation of a non-standard approach to the preparation of a Ni/MgO catalyst. The catalyst required for MWCNTs synthesis was obtained through chemical vapor deposition method. At the same time, the pre-catalyst was treated by electromagnetic field, ultrasound and microwave waves methods. It was proved that the treatment of the catalyst initial components solution with the electromagnetic field, ultrasound and microwaves contributes to an increase in the yield of the synthesized MWCNTs by 50, 30 and 70%. Besides, ultrasonic treatment may be used if MWCNTs of relatively low degree of a defect are required. The proposed approach is economically feasible since small additional energy costs lead to a more complete conversion of carbon-containing raw materials into the target product at the activation stage. The reported method may be used to prepare MWCNTs of different types economically; leading to its industrial application to produce different types of MWCNTs.

Electron Dynamics in the Field of Strong Plasma and Electromagnetic Waves: A Review

Collective methods of charged particle acceleration provide an approach towards achieving high-energy particle beams with relatively compact accelerator facilities. Among the collective acceleration methods, one of the central places belong to the electron Laser Wakefield Acceleration concept, when the regular accelerating structure in the form of longitudinal electrostatic wave propagating with the phase speed close to speed of light in vacuum is generated by ultrashort laser pulse in collisionless plasma. The review article contains theoretical description of charged particle (electron) interaction with various configurations of the electromagnetic field and with the longitudinal plasma waves. The radiation dominated regimes of the electron interaction with strong electromagnetic waves, when the radiation friction force effects play the key role, are also discussed.

Влияние пространственной дисперсии в металлах на оптические характеристики биметаллических плазмонных наночастиц

The problem of diffraction of an electromagnetic plane wave field on a core-shell nanoparticle composed of two plasmon metals is considered. The effect of spatial dispersion in metals on the absorption cross section is investigated on the basis of the Discrete Sources method. Various combinations of core and shell metals: Au@Ag and Ag@Au of spheroidal particles, as well as the effect of elongation and asymmetry of particle geometry on energy absorption are being studied. It was found that taking into account the spatial dispersion, both in the core and in the shell, leads to a significant decrease in the absorption cross section and a shift of the plasmon resonance to the shorter wavelength region.

Generation of Gravitational Waves by a Standing Electromagnetic Wave

The process of generating gravitational waves by a standing electromagnetic wave is considered. The description of gravitational waves coupled with the electromagnetic field is carried out on the basis of linearized Einstein gravity. It is shown that such gravitational-electromagnetic waves inside a Fabry-Perrot resonator lead to generation of the usual high-frequency transverse-traceless gravitational waves which propagate in two mutually opposite directions in empty space outside the resonator. A comparison of gravitational waves coupled with the electromagnetic field and free waves in empty space is carried out.

Electromagnetic waves between mutually moving radiator and receiver

A flat one-dimensional field of electromagnetic waves described by Maxwell's equations is considered. In the framework of solving the Cauchy problems of hyperbolic equations, we study the period of harmonic waves on the receiver for different versions of the relative motion of the radiator and receiver. Formulas for the ratio of the periods of generated and received waves are obtained. It is found that when the relative motion of the radiator and receiver is relative to each other, the receiver receives waves of a different period that creates a generator on the radiator. When the radiator and receiver approach, the wave period shortens, and when they are removed from each other, the wave period lengthens. These phenomena are known to practical physics and are called blue and red shifts. The formulas allow us to see that at a constant velocity of mutual movement, there is a qualitative difference in the periods of received waves, when the radiator is moving and the receiver is stationary, and, conversely, when the receiver is moving and the radiator is stationary. For all variants of the mutual movement of the radiator and receiver, the Doppler effect formulas are obtained. What is remarkable is that the Doppler effect does not change because the radiator is moving and the receiver is stationary, or, conversely, the receiver is moving and the radiator is stationary. This is also observed when the radiator overtakes a moving receiver or, conversely, the receiver overtakes a moving radiator. It is concluded that mathematical models of the detected physical effects are a manifestation of the physical properties of the medium in which electromagnetic waves propagate – a medium called the emptiness. In the near future, humanity will enter deep space and reach velocities comparable to the light velocity. This will make it possible to conduct experiments with vehicles moving relative to each other and obtain results of direct observations of the physical properties of the emptiness. These experiments are extremely important because they will lead humanity to the knowledge of the properties of what has become, as it can be assumed, the basis of all that we directly or indirectly observe in the world around us.

Моделирование спектров люминесценции в сферических микрорезонаторах с излучающей оболочкой

The luminescence spectra of a microresonator structure consisting of a spherical core of small diameter (3.5 – 6 mcm) covered with a luminescent shell with a refractive index less than that of the core are modeled. Shell luminescence spectra, radial distribution of the whispering gallery mode (WGM) field, and mode parameters (wavelength, width, quality factor) are calculated using the expansion of the electromagnetic wave field in the basis of vector spherical harmonics and the method of spherical wave transfer matrices. The dependence of the luminescence spectra and WGM parameters on the geometric and optical parameters of the structure - the shell thickness, the refractive index of the shell, and the core diameter - is studied.

Multifrequency optimization method of measurement the frequency dependency of electrophysical parameters of dielectric and magnetodielectric coatings

The issues of experimental determination of electrodynamic parameters of existing and new synthesized materials and coatings used in the microwave range are highlighted. Problems arising from measurements of the electrophysical and geometric parameters of dielectric and magnetodielectric coatings, taking into account their placement on a metal substrate, by radio wave methods are considered. We present the new radio wave method of joint measurements of the frequency dependence of the complex permittivity, the frequency dependence of the complex magnetic permeability, and the thickness of plane-layered samples of dielectric and magnetodielectric coatings on a metal substrate. Determination of electrophysical and geometric parameters of the coating in the proposed method 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 simulation model of measurements is shown, implemented on the basis of the electrodynamic modeling system CST Microwave studio (Simulia corporation, USA) and the Matlab system. The results of simulation are presented to determine the frequency dependences of the electrophysical parameters and the thickness of a sample of a radio-absorbing coating on a metal substrate. Errors in the estimates of permittivity and permeability in the measurement frequency band 9–13.5 GHz, which are no more than 10 % with a confidence level of 0.95 with a mean square deviation of the noise level of 0.006, have been obtained. The proposed method can be in demand in various science-intensive areas – microelectronic, aerospace, mechanical engineering, etc.

Reverse-Time Migration by Combining Laplacian Filtering With Wavefield Decomposition for High-Resolution Subsurface Imaging

Reverse-time migration (RTM) is considered to be one of the most accurate migration methods, especially for imaging geologically complex structures. However, the conventional RTM using cross-correlation imaging condition is subject to strong migration artifacts. Recent researches on electromagnetic wavefield decomposition exhibit that the method can greatly suppresses the internal reflection noise, however, it is still subject to residual noise. To further eliminate the low-frequency noise to obtain high-resolution subsurface image, a novel electromagnetic imaging scheme by combining a Laplacian filtering with wavefield decomposition is presented, and the pseudospectral time-domain (PSTD) method is introduced to solve the time-dependent partial differential equations efficiently. In this work, we apply the Laplacian filtering on each wavefield snapshot in space domain to sharpen the field distribution. The filtered wavefields are further decomposed into downgoing and upgoing components for final imaging. Numerical experiments show that the proposed method balances the amplitudes of reflectors, and exhibits higher resolution compared to the conventional RTM.

Parametric resonance in the ultracold Rydberg plasma under the influence of an acoustic wave

The article considers weakly ionized ultracold Rydberg plasma under the influence of an acoustic wave of the terahertz range. The effect of an acoustic wave on Langmuir oscillations of Rydberg plasma is described using a hydrodynamic approach. The mechanism of the influence of an acoustic wave on Langmuir oscillations in such plasma, which consists in the scattering of electrons by neutral atoms oscillating in a high-frequency acoustic field, is considered. The unitary Kramers—Henneberger transformation in the Schrцdinger equation is used to calculate the cross section for the scattering of electrons by atoms performing high-frequency oscillations in the field of a terahertz acoustic wave. On this basis, a deep analogy is shown between the problem of scattering of an electron in the field of an external electromagnetic wave by a stationary atom and the problem of scattering of an electron by an atom vibrating in an external acoustic field. Numerical calculations demonstrate the oscillatory character of the cross section for the scattering of an electron by a Rydberg atom vibrating in a high-frequency acoustic field. Within the framework of the chosen hydrodynamic model, in view of the time dependence of the cross section for scattering of electrons by plasma atoms, the change in the electron density in such a system is described by the Mathieu equation, well known in mathematical physics. On the basis of this equation, the fundamental possibility of the appearance of parametric resonance, in the form of the buildup of Langmuir oscillations, in such a system is shown theoretically. The conditions for the appearance of resonance in Rydberg plasma initiated by a high-frequency acoustic wave are indicated.

Experimental studies on the mechanism of seismoelectric logging while drilling with multipole source

SUMMARYWhen a seismic wave propagates in a fluid-saturated porous medium, a relative movement forms between the solid and the fluid and induces an electric current due to the electronic double layer. As a result, two kinds of seismoelectric coupling responses are generated in this procedure: the localized electric/magnetic field and interfacial electromagnetic wavefield. One important potential application of these two seismoelectric conversions is used for measuring formation P and S waves in well logging. Considering that the strong collar wave seriously affects the velocity measurements of formation P and S waves in current acoustic logging while drilling (LWD), the seismoelectric LWD method, which combines seismoelectric conversion and acoustic LWD technique, was suggested to be a novel method in oil and gas exploration. The collar wave cannot induce any seismoelectric signal on the metal collar since there is no double layer formed on a metal surface. In this paper, acoustic and seismoelectric LWD measurements are conducted in the laboratory. We build a scaled multipole acoustic LWD tool to conduct acoustic measurements in a water tank and a sandstone borehole model. We also build a multipole seismoelectric LWD tool and record the seismoelectric signals induced with the same acoustic source. Then, we compare the recorded acoustic and seismoelectric signals by using the experimental data. The result indicates that the apparent velocities of seismoelectric signals are equal to the formation P- and S-wave velocities and the collar waves do not induce any visible electric signal in the full waveforms. We further analyse the mechanism of seismoelectric LWD by a quantitative comparison of the amplitudes between the inner collar wave and outer collar wave. The results show that the amplitude of outer collar wave decreases significantly when it radiates out of the tool, so that the seismoelectric signals induced by collar waves are too weak to be distinguished in the full waveforms of seismoelectric LWD measurements. Thus, the formation P- and S-wave velocities are detected accurately from the recorded seismoelectric LWD data. These results verify the feasibility of the seismoelectric LWD method for measuring acoustic velocities of the borehole formation.

Electromagnetic interference shielding anisotropy enhanced by CFRP laminated structures

Continuous carbon fiber reinforced polymers (CFRP) composites, particularly prepreg stacked composites, have anisotropic properties, including anisotropy of electrical conductivity and dielectric characteristics. These features lead to electromagnetic interference (EMI) shielding anisotropy of the CFRP. The coaxial transmission line method was used to test the EMI shielding of CFRP to clarify the EMI shielding anisotropy of CFRP. Moreover, the optimization of EMI shielding performance of CFRP by changing the composites’ structure were also investigated systematically. The anisotropy of EMI shielding was confirmed for the first time by the coaxial transmission line method. The results showed that a quasi-radial sample had the highest shielding effectiveness (25.8 dB) at 15 GHz, and the carbon fibers in this sample aligned in the direction of the electric field of electromagnetic waves. The orientation of fibers relative to the direction of electric field clearly affected the EMI shielding performance of the CFRP composites. The four-ply CFRP (0°/90°/0°/90°) with three cross-layers had the excellent shielding value of 28.9 dB at 15 GHz, that was far superior to that of a unidirectional CFRP (0°/0°/0°/0°) composite (SE = 18.6 dB), and it even outperformed an eight-ply unidirectional CFRP composite (SE = 22.6 dB). Laminated structures governed SE, and the number of cross-layers in the composites improved their EMI shielding performance. The shielding mechanisms of cross-layer CFRPs were also discussed and clarified based on both experimental and theoretical analysis. We believe that these findings could provide a scientific basis and potential in designing high-performance EMI shielding materials.

Non-Invasive Blood Glucose Monitoring Technology: A Review.

In recent years, with the rise of global diabetes, a growing number of subjects are suffering from pain and infections caused by the invasive nature of mainstream commercial glucose meters. Non-invasive blood glucose monitoring technology has become an international research topic and a new method which could bring relief to a vast number of patients. This paper reviews the research progress and major challenges of non-invasive blood glucose detection technology in recent years, and divides it into three categories: optics, microwave and electrochemistry, based on the detection principle. The technology covers medical, materials, optics, electromagnetic wave, chemistry, biology, computational science and other related fields. The advantages and limitations of non-invasive and invasive technologies as well as electrochemistry and optics in non-invasives are compared horizontally in this paper. In addition, the current research achievements and limitations of non-invasive electrochemical glucose sensing systems in continuous monitoring, point-of-care and clinical settings are highlighted, so as to discuss the development tendency in future research. With the rapid development of wearable technology and transdermal biosensors, non-invasive blood glucose monitoring will become more efficient, affordable, robust, and more competitive on the market.