Behavior Of Electromagnetic Waves Research Articles

Elucidating the coherent and incoherent reflection of plane-waves in finite thickness media: a practical pedagogical application

The propagation of light through a thin film interfaced between two semi-infinite media serves as a compelling illustration for elucidating electromagnetic wave interactions with matter at the undergraduate level. Despite its pedagogical significance and diverse technological applications, this model often receives inadequate attention in foundational electromagnetism literature, limiting early student exposure to this emblematic concept. In this pedagogical initiative, we present a comprehensive analysis of electromagnetic wave propagation through a dielectric medium positioned between semi-infinite media. We examine interference phenomena arising from back-and-forth reflected waves within the dielectric, focusing on the coherent and incoherent reflection regimes as limiting cases. Employing rigorous analytical treatment, we delineate transmittance and reflectance profiles, offering students a lucid understanding of how the refractive index’s real and imaginary components compete and manifest under specific conditions. This analytical approach enhances students’ comprehension of electromagnetic wave behavior within diverse mediums. Furthermore, we extend this theoretical foundation to practical applications, emphasizing renewable energy contexts. By calculating absorptance, we estimate the maximum photo-generated current and power conversion efficiency of a prototype solar cell, establishing a tangible link between theoretical knowledge and real-world solar energy utilization.

Analysis of Moving Bodies with a Direct Finite Difference Time Domain Method

This paper proposes an original and thorough analysis of the behavior of electromagnetic waves in the presence of moving bodies by using the finite difference time domain (FDTD) method. Movements are implemented by changing positions of the objects at each time step, through the classical FDTD time loop. This technique is suitable for non-relativistic speeds, thus for most encountered problems in antennas and propagation domain. The numerical aspects that need to be considered are studied. Then, different bodies in motion are examined: plane wave source with matching resistors, observation point, inclined partially reflecting surface (PRS), line source, and metallic cylinder illuminated by a plane wave. The results are compared with those of special relativity which are considered as the references. Some aspects of special relativity are present in the direct FDTD approach, such as the independence of the velocity of electromagnetic wave propagation with the speed of the source and Lorentz local time (with a different physical interpretation). It is shown that the amplitude of the electric field for a moving plane wave source does not increase with the speed of motion, if the impedance of the source is small. Moreover, for a moving scattering metallic wire, one can observe a phenomenon similar to shock waves.

Dielectric‐Based Metamaterials for Near‐Perfect Light Absorption

AbstractThe emergence of metamaterials and their continued prosperity have built a powerful working platform for accurately manipulating the behavior of electromagnetic waves, providing sufficient possibility for the realization of metamaterial absorbers with outstanding performance. However, metamaterial absorbers composed of metallic materials typically possess many unfavorable factors, such as non‐adjustable absorption, easy oxidation, low‐melting, and expensive preparation costs. The selection of dielectric materials provides excellent alternatives due to their remarkable properties, thus dielectric‐based metamaterial absorbers (DBMAs) have attracted much attention. To promote breakthroughs in DBMAs and guide their future development, this work systematically and deeply reviews the recent research progress of DBMAs from four different but progressive aspects, including physical principles; classifications, material selections and tunable properties; preparation technologies; and functional applications. Five different types of theories and related physical mechanisms, such as Mie resonance, guided‐mode resonance, and Anapole resonance, are briefly outlined to explain DBMAs having near‐perfect absorption performance. Mainstream material selections, structure designs, and different types of tunable DBMAs are highlighted. Several widely utilized preparation methods for customizing DBMAs are given. Various practical applications of DBMAs in sensing, stealth technology, solar energy absorption, and electromagnetic interference suppression are reviewed. Finally, some key challenges and feasible solutions for DBMAs’ future development are provided.

Entropy engineering enhances the electromagnetic wave absorption of high-entropy transition metal dichalcogenides/N-doped carbon nanofiber composites.

Entropy engineering strategies provide a broader platform for exploring the behavior of electromagnetic wave (EMW) absorption materials and their absorption mechanisms on the microscopic scale. In this work, a novel entropy engineering strategy was developed to improve the EMW absorption properties of MoS2. A hierarchical N-doped carbon nanofiber/MoS2 (NCNF/MS) composite was synthesized using the electrospinning and hydrothermal methods. Then, the conformational entropy of MoS2 was increased by sequentially integrating elements such as W, Se, and Te. Although MoS2 maintains a single 2H-phase structure throughout the entropy increase process, it triggers a series of complex changes at the microscopic level, including lattice distortion, ingenious electronic structure adjustments, and an increase in defect density. These changes provide more possibilities for the EMW interaction with the absorber, which significantly enhances the dielectric behavior of the composites, including conduction and polarization losses. Owing to the unique hierarchical structure and rich defect structure, the obtained entropy-increased NCNF/MWSST exhibits excellent EMW absorption performance. The minimum reflection loss reaches -60.7 dB, and the maximum effective absorption bandwidth is 6.48 GHz, which is improved by almost 584% and 810% compared to NCNF/MS. This study provides a new way to design efficient and high-performance MoS2-based absorbers and provides valuable insights for exploring the entropy-increasing strategies to optimize the EMW absorption properties.

Direct Electromagnetic Wave Scattering Calculation Using Methods of Moments through Layered Rough Surface

This thesis focuses on the direct calculation of electromagnetic wave scattering through layered rough surfaces using the Method of Moments. The study aims to contribute to existing knowledge by addressing the problems associated with accurately predicting scattered electromagnetic fields from rough surfaces with layered structures. By using the Method of Moments, this research seeks to provide insights into the behavior of electromagnetic waves when interacting with multi-layered rough surfaces, offering valuable implications for practical engineering applications and the development of advanced computational tools for electromagnetic wave analysis. In practical terms, the surface is typically divided into small patches, and the electromagnetic field at each patch is determined using MoM. This involves solving integral equations describing the interaction between the induced currents on the surface and the incident field. The layered structure may require additional equations to model the reflection of waves and the transmission at the boundaries between the layers. The direct problem is also examined in a two-dimensional picture, where the rough surface profile and the medium are known parameters, and the electromagnetic waves scattered from the surface to the entire space are the unknowns. The rough surface is considered to have a finite length and can be deterministic or arise from a stationary stochastic random process, with a focus on Gaussian-type rough surfaces. The roughness is considered as two basic types: as a perfect electric conductor (PEC) in free space and as a boundary between two dielectric media. The equations of integration obtained are based on the scalar solution of Green's theory, Helmholtz equations, and using Hankel type green functions as kernels due to the one-dimensional nature. The MoM is extensively used to solve these integral equations and is compared to asymptotic approaches and analytical. Various simulations are conducted to test the feasibility of the algorithms, and the results are thoroughly discussed. The study of electromagnetic wave scattering in one-dimensional rough surfaces involves the direct problem, where the field distribution in the whole space is determined using the equation of integration. These equations take into account the surface roughness and medium parameters they are solved using the Method of Moments (MoM) by expressing the field distribution on the surface using basis functions. The direct calculation of electromagnetic wave scattering through a layered rough surface using the Method of Moments (MoM) is a computationally intensive process and complex and. It contains simulating the interaction of EM waves with a complex surface, which presents challenges due to the multiple layers with different properties, and a roughly surface causing and diffraction of incident waves and scattering. When working with a layered rough surface increases the electromagnetic wave interaction complexity. Additional multiple layers introduce considerations, such as layer interfaces and accounting for different material abilities. This requires careful modeling and analysis to exactly capture the behavior of electromagnetic waves as they traverse through and interact with layers. MoM, a commonly used numerical method for solving electromagnetic scattering problems, discreteness the surface into small segments and solves integral equations to determine the fields that is scattered. This approach allows for a maximum analysis of electromagnetic interactions at a grained level.

Implementation of the Hybrid ADI-FDTD Scheme to Maxwell Equation for Mathematical Modeling of Breast Tumor

Breast cancer is the most common cancer in women, and non-destructive detection of the tumor is vital. The interaction of electromagnetic waves with breast tissue and the behavior of waves after interaction are used to model tumor detection mathematically. The behavior of electromagnetic waves in a medium is described using Maxwell's equations. Electromagnetic waves propagate according to the electrical properties of a medium. Since the electrical properties of tumor tissue are different from those of normal breast tissue, it is assumed that the tumor is a lossy dielectric sphere, and the breast is a lossy dielectric medium. Under this assumption, Maxwell's equations are used to calculate the scattered field from the tumor. The field scattered by the tumor is different from other tissues because their dielectric properties are different. The location and size of the tumor can be determined by utilizing the difference in scattering from the tissues. While the scattering field from the tumor in spherical geometric form is analytically calculated, it is not analytically possible to calculate the scattering field from the tumor in different geometric shapes. In addition to non-destructive detection of the tumor, an efficient numerical method, the finite difference time domain method (FDTD), is used to simulate the field distribution. After the location of the tumor is determined, the Alternating Direction Implicit (ADI) FDTD method, which gives simulation results by dividing the computation domain into smaller sub-intervals, can be used. Scattered fields are calculated analytically in the geometry where the tumor is in the form of a smooth sphere, and in more complex geometry, the field distributions are successfully obtained with the help of MATLAB using FDTD and ADI-FDTD algorithms.

An all-silicon design of a high-efficiency broadband transmissive terahertz polarization convertor

Polarization, a fundamental behavior of electromagnetic waves, holds immense potential across diverse domains such as environmental monitoring, biomedicine, and ocean exploration. However, achieving efficient modulation of terahertz waves with wide operational bandwidth poses significant challenges. Here, we introduce an all-silicon polarization converter designed specifically to operate in the terahertz range of the electromagnetic spectrum. Simulation results demonstrate that the average conversion efficiency of cross-linear waves exceeds 80% across a wide frequency range spanning from 1.00 to 2.32 THz, with the highest conversion efficiency peaking at an impressive 99.97%. Additionally, our proposed structure facilitates linear-to-circular polarization conversion with an ellipticity of 1 at 0.85 THz. Furthermore, by rotating the cross-shaped microstructure, active control over arbitrary polarization states can be achieved. To summarize, the proposed structure offers remarkable flexibility and ease of integration, providing a reliable and practical solution for achieving broadband and efficient polarization conversion of terahertz waves.Graphical abstract

Simulation of Electromagnetic Waves in Magnetized Cold Plasma by a Novel BZT-DGTD Method

This work presents a novel discontinuous Galerkin time domain (DGTD) approach based on second-order bilinear <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">z</i> transform (BZT) to analyze the behavior of electromagnetic waves in a magnetized cold plasma. The Maxwell’s equations and current density equation are utilized to formulate the governing mathematical expressions of magnetized plasma, and the BZT approach is employed to construct the time domain iterative formula. The suggested technique outperforms existing methods in terms of stability, performance, and aliasing effect avoidance. The efficacy of the suggested BZT-DGTD approach is investigated by analyzing electromagnetic wave propagation in unmagnetized and magnetized cold plasmas, and a comprehensive comparison is performed with commercial software WCT and COMSOL to validate its practicality. Furthermore, the features of electromagnetic wave propagation in plasma are investigated under numerous circumstances, and these instances are compatible with plasma physics.

Tunable dynamic metamaterial for negative refraction

The effective ability to manipulate the negative refraction behaviors of electromagnetic waves in the terahertz (THz) frequency range is of great interest for various practical applications in communication, imaging, and sensing. In this study, we propose a robust graphene-integrated metamaterial design for the dynamic manipulation of negative refraction at terahertz frequencies. Using the distinctive characteristics of graphene combined with the specially designed metamaterial structure, we demonstrated the active control of negative refraction by modulating the graphene's chemical potential from 0.0 to 1.0 eV. By dynamically tuning the carrier density of graphene, we create the switchable states of the negative index for the transmission or the reflection modes, tailoring the terahertz wave behavior in real time. In particular, in the case of different applied temperatures (through the bias applied voltages) of the proposed metamaterial, these two modes are maintained over 60% for both reflection and transmission while preserving the negative refractive index. Our results reveal the tunability of negative refraction, paving the way for developing reconfigurable THz meta-devices with enhanced functionalities in the near future.

Analytical study of nonlinear models using a modified Schrödinger’s equation and logarithmic transformation

Optical solitons are special waves that maintain their shape while traveling. Hence, solitary optical waves have great significance when it comes to representing pulse propagation through nonlinear partial differential equations. In our research, we have uncovered unique solutions for the formation of solitary wave patterns in the equation of the Heisenberg ferromagnetic spin chain (HFSC). This equation aptly describes the behavior of electromagnetic waves in contemporary magnetism. By employing innovative techniques based on logarithmic transformations and analytical methods, we have obtained various solution forms expressed in a concise manner using elementary functions. We have tested the correctness of these solutions by substituting them directly into the main equation. These recent discoveries provide novel perspectives on the complex realm of solitons as depicted by this model. Moreover, since the model finds applications in fiber optic communications, fluid dynamics, and other fields, the implications of these discoveries are broad. The utilized methods stand out for being simple, reliable, and capable of creating fresh solutions for nonlinear partial differential equations in the realm of mathematical physics. The research findings presented here showcase the effectiveness of the applied methods in reliably studying nonlinear phenomena in the HFSC equation and other nonlinear problems in mathematical physics. By utilizing these tools, scholars have the opportunity to expand and enhance their understanding of the complex mathematical frameworks underlying real-world problems.

Spray deposited Graphene@MXene on a flexible polymer substrate for Terahertz Shielding

The rapid progress in telecommunications over the past decade brought about a societal revolution. However, the proliferation of electromagnetic waves has also presented significant challenges that require our attention. In this regard, we presented a simple spray-coating method for developing a lightweight and flexible graphene-coated MXene film for terahertz shielding. The MXene/graphene layered structure, with a 3:1 wt ratio and a thickness of 1.63 μm, achieved a shielding effectiveness (SE) of 47 dB, which was remarkably similar to that of the pristine MXene with a thickness of 0.8 μm. Notably, even after one month of storage, the SE of the composite consisting of 75 wt % MXene-25 wt % Graphene remained at 94% of its initial value. In contrast, the SE was reduced to 72% of its initial value in the case of 100 wt % MXene. The hydrophobic graphene layer, acting as a barrier against water molecules, emerged as the key factor responsible for maintaining the shielding efficiency. Furthermore, theoretical modeling based on the transfer matrix method was employed to correlate the behavior of electromagnetic waves at different interfaces of thin films.

Magnetic array vertically anchored on flexible carbon cloth with “magical angle” for the increased effective absorption bandwidth and improved reflection loss simultaneously

Increasing electromagnetic pollution has put new demands on the development of high-performance microwave absorbing materials. In this paper, for the first time, a highly conductive flexible carbon cloth-based (CC-based) substrate is realized to tune the structure of the material at the macroscopic scale (centimeter-scale). The change of stacking mode is found to play a crucial role in the response behavior of electromagnetic waves of CC. When the stacking angle is 45°, the CC is more prone to phase-to-cancellation behavior. Bimodal absorption occurs in the 2–18 GHz frequency band and succeeds in tripling its effective absorption bandwidth (from 2.24 GHz to 7.44 GHz). The in situ growth of magnetic mace-like NiCo2O4 on CC further breaks the limitation of a single loss mechanism inside CC and innovatively enables the construction of centimeter-scale microcurrent networks and magnetic coupling networks. Moreover, the 1D nanopin arrays anchored on CC substrates also help to provide numerous heterostructures with strong interfacial polarization behaviors, multiple scattering points, and good impedance matching capability, further improving the microwave absorption performance. Thus CC@NiCo2O4 achieves a reflection loss (RL) value of −54.1 dB at 14.08 GHz with an effective absorption bandwidth (EAB) of 6.3 GHz (11.7–18 GHz) at a thickness of only 2 mm. This work provides new ideas for the design and preparation of high absorption capacity and wide broadband response from both macroscopic and microscopic scales.

Density oscillation of plasma sheath and its influence on electromagnetic wave behavior

Density oscillation of plasma sheath and its influence on electromagnetic wave behavior

High-Order Orbital and Spin Hall Effects at the Tight Focus of Laser Beams

In this paper, using a Richards–Wolf method, which describes the behavior of electromagnetic waves at the sharp focus, we show that high-order spin and orbital Hall effects take place at the focal plane of tightly focused laser beams. We reveal that four local subwavelength regions are formed at the focus of a linearly polarized optical vortex with unit topological charge, where the spin angular momentum behaves in a special way. Longitudinal projections of the spin angular momentum are oppositely directed in the adjacent regions. We conclude that this is because photons falling into the neighboring regions at the focus have the opposite spin. This newly observed phenomenon may be called a spin Hall effect of the 4-th order. We also show that tightly focusing the superposition of cylindrical vector beams of the m-th and zero-order produces 2m subwavelength regions in the focal plane, such that longitudinal projections of the orbital angular momentum are oppositely directed in the neighboring regions. This occurs because photons falling into the neighboring regions at the focus have the opposite signs of the on-axis projections of the orbital angular momentum. This phenomenon may be termed an orbital Hall effect of the 2m-th order.

Mechanism of color change of flexible metafilm with structural parameters and stretching methods

Color change metafilm is promising for the color printing of displays and imaging. A metallic array on an elastic film can realize dynamic color change by mechanical extensions, such as uniaxial or biaxial stretching. In this study, an electromagnetic model of a flexible metafilm composed of a microscale Al cylindrical array on a polydimethylsiloxane elastic film was constructed to study the underlying optical mechanism of color change, especially brightness and saturation changes, of the flexible metafilm with structural parameters (diameter and height of the Al cylinders) and stretching methods (uniaxial or biaxial stretching). The 3D finite time domain difference method was used to simulate the propagation behavior of electromagnetic waves through metafilm. With increasing diameter, the lightness increases while the saturation decreases, which is due to the change of surface plasmon resonance from local surface plasmon resonance (LSPR) to propagation surface plasmon (PSP) and Wood Anomaly (WA) and finally to magnetic polariton excitation. With increasing height, lightness first decreases and then increases, while the change in saturation is opposite, which is due to the first increasing and then decreasing of the intensities of PSP and WA. By comparing the dynamic color changes of metafilm under uniaxial stretching and biaxial stretching, it is found that uniaxial stretching achieves lower lightness and saturation under small strain and higher lightness and saturation under large strain, which is caused by the enhanced WA and PSP on the Al-air interface at short wavelengths and the weakened LSPR on the Al-PDMS interface at long wavelengths. This discovery paves the way for practical applications of structural color display with high saturation and brightness.

Guiding and Leakage Dispersion Characteristic of TM01Mode in a Circular Dielectric Rod

Open dielectric waveguide structures such as circular dielectric rods can be used as antennas by leaking energy in the transverse direction or as guiding structures with low loss in integrated circuits at different frequency ranges. It is essential to understand electromagnetic wave behavior in different frequency regions such as reactive mode region, leaky-wave or antenna mode region, and guided mode region. In this study, it is aimed to assimilate the electromagnetic phenomenon for open dielectric structure by showing the overlapping between the analytic solutions and the simulation results of the TM01 mode of the circular dielectric rod. The analytic solutions for leaky-wave modes have been obtained using the coefficients matrix of the system of characteristic equations of the structure and Davidenko’s method. The field distributions and the scattering parameters have been obtained in CST microwave studio software. The outcomes obtained in the study presented the overlapping between the analytical results and the simulations. The simulation results show the leakage starts end of the reactive mode region where the electromagnetic energy reflects to the feed line, and the electromagnetic energy leaks at the leaky-wave/antenna mode region, and the leakage decreases at the guided mode region as much as it can be neglected while the frequency increases.

Preparation and Microwave Absorbing Properties of Yolk Shell C@C Microspheres

As a typical dielectric loss medium, carbon material has always been the most attractive candidate material for microwave absorption because of its characteristic advantages. However, much less attention has been paid to the reasonable design of micro-structure to improve its performance. According to the transmission behavior and loss mechanism of electromagnetic wave, uniform yolk shell C@C microspheres as a new type of microwave absorbers were creatively prepared by "coating-coating-etching". Compared with solid carbon microspheres, the unique micro-structure endows better BET surface and pore volume to the yolk shell C@C microspheres. The microwave absorption performance was tested in the frequency range of 2GHz to 18GHz. As expected, the yolk shell C@C microspheres exhibit excellent reflection loss characteristics, with strong reflection loss (-41.84dB at 9.2GHz) and wide effective absorption bandwidth(7.9~10.2GHz). This good performance is so for indeed better than most pure carbon absorbers reported. The electromagnetic parameters show that the yolk shell structure is conducive to the matching of characteristic impedance and can obtain ideal microwave absorption ability.

Comparison of 920 MHz and 2.4 GHz Near Ground Electromagnetic Wave Pathloss Propagation Model for Wireless Sensor Network in Forest Environment Application

A Wireless Sensor Network (WSN) system that uses wireless communication technologies occasionally experiences data loss when undertaking wireless data communication. This problem happens because of the WSN system being placed on top of the ground and surrounded by vegetation that adds more loss to the transmission. In order to avoid this problem, the wireless system design must meet its best performance. To build the best performing WSN system, electromagnetic wave behavior in the forest environment needs to be studied well. This paper investigates the electromagnetic wave behavior transmitted and propagated by a WSN node at less than 30 cm from the ground using a 920 MHz frequency. We have analyzed that low height (30 cm) and vegetation environments can also add more loss at about 30.96 dB to the free space pathloss model. The new 920 MHz (that adds 30.96 dB loss) model shows identical behavior to 2.4 GHz with an average difference of 12.24 dB. However, the 920 MHz model performs better, achieving an average RMSE of 1.06 compared with the 2.4 GHz model, which can only achieve an average RMSE of 4.92 compared with the 920 MHz measurement.

Diffusion of elastic waves in a continuum solid with a random array of pinned dislocations

The propagation of incoherent elastic energy in a three-dimensional solid due to the scattering by many, randomly placed and oriented, pinned dislocation segments, is considered in a continuum mechanics framework. The scattering mechanism is that of an elastic string of length L that re-radiates as a response to an incoming wave. The scatterers are thus not static but have their own dynamics. A Bethe-Salpeter (BS) equation is established, and a Ward-Takahashi Identity (WTI) is demonstrated. The BS equation is written as a spectral problem that, using the WTI, is solved in the diffusive limit. To leading order a diffusion behavior indeed results, and an explicit formula for the diffusion coeffcient is obtained. It can be evaluated in an Independent Scattering Approximation (ISA) in the absence of intrinsic damping. It depends not only on the bare longitudinal and transverse wave velocities but also on the renormalized velocities, as well as attenuation coeffcients, of the coherent waves. The influence of the length scale given by L, and of the resonant behavior for frequencies near the resonance frequency of the strings, can be explicitly identified. A Kubo representation for the diffusion constant can be identified. Previous generic results, obtained with an energy transfer formalism, are recovered when the number of dislocations per unit volume is small. This includes the equipartition of diffusive energy density which, however, does not hold in general. The formalism bears a number of similarities with the behavior of electromagnetic waves in a medium with a random distribution of dielectric scatterers; the elastic interaction, however, is momentum dependent.

Experimental studying the propagation and absorption of electromagnetic waves on various rock-forming minerals in Uzbekistan

The nature of wave propagation often depends on the frequency and on the type of radiation used. The main goal of these technologies is to bring into development low-permeability isolated zones of the reservoir by exposing them to elastic waves that attenuate in high-permeability sections of the reservoir, but propagate over considerable distances and with sufficient intensity to excite low-permeability sections of the reservoir. In this paper, a more in-depth study of the propagation and absorption of electromagnetic waves through various minerals contained in rock was considered, in particular, the behavior of electromagnetic waves through rock with different moisture contents (water molecules) and clay particles (aluminosilicates) was studied. It was found that the radiative power reached the highest value at 0.01 distance, which was 506 at 10% water content, followed by 505 at 20% water content, 504 at 30% water content, 502 at 40% water content, 500 at 50% water content, and it was 498 when water content was 60%.