Electromagnetic Waves Research Articles

Photonic Dirac waveguide in inhomogeneous spoof surface plasmonic metasurfaces

Abstract The metamaterial with artificial synthetic gauge field has been proved as an excellent platform to manipulate the transport of the electromagnetic wave. Here we propose an inhomogeneous spoof surface plasmonic metasurface to construct an in-plane pseudo-magnetic field, which is generated by engineering the gradient variation of the opened Dirac cone corresponding to spatially varying mass term. The chiral zeroth-order Landau level is induced by the strong pseudo-magnetic field. Based on the bulk state propagation of the chiral Landau level, the photonic Dirac waveguide is designed and demonstrated in the experimental measurement, in which the unidirectionally guided electromagnetic mode supports the high-capacity of energy transport. Without breaking the time-reversal symmetry, our proposal structure paves a new way for realizing the artificial in-plane magnetic field and photonic Dirac waveguide in metamaterial, and have potential for designing integrated photonic devices in practical applications.

Second-harmonic generation tensors from high-throughput density-functional perturbation theory

Optical materials play a key role in enabling modern optoelectronic technologies in a wide variety of domains such as the medical or the energy sector. Among them, nonlinear optical crystals are of primary importance to achieve a broader range of electromagnetic waves in the devices. However, numerous and contradicting requirements significantly limit the discovery of new potential candidates, which, in turn, hinders the technological development. In the present work, the static nonlinear susceptibility and dielectric tensor are computed via density-functional perturbation theory for a set of 579 inorganic semiconductors. The computational methodology is discussed and the provided database is described with respect to both its data distribution and its format. Several comparisons with both experimental and ab initio results from literature allow to confirm the reliability of our data. The aim of this work is to provide a relevant dataset to foster the identification of promising nonlinear optical crystals in order to motivate their subsequent experimental investigation.

Fe3O4 Nanoparticles Embedded into Pyridinic-N-Rich Carbon Nanohoneycomb with Strong dx2-Pz Orbital Hybridization for High-Performance Electromagnetic Wave Absorption.

Carbon-based magnetic nanocomposites as promising lightweight electromagnetic wave (EMW) absorbents are expected to address critical issues caused by electromagnetic pollution. Herein, Fe3O4 nanoparticles embedded into a 3D N-rich porous carbon nanohoneycomb (Fe3O4@NC) were developed via the pyrolysis of an in-situ-polymerized compound of m-phenylenediamine initiated by FeCl2 in the presence of NaCl crystals as templates. Results demonstrate that Fe3O4@NC features highly dispersed Fe3O4 nanoparticles into an ultrahigh specific pyridinic-N doping carbon matrix, resulting in excellent impedance matching characteristics and electromagnetic wave absorbing capability with the biggest effective absorption bandwidth (EAB) of up to 7.1 GHz and the minimum reflective loss (RLmin) of up to -65.5 dB in the thin thickness of 2.5 and 2.3 mm, respectively, which also outperforms the majority of carbon-based absorbers reported. Meanwhile, its high absorption performance is further demonstrated by an ethylene propylene diene monomer wave absorbing patch filled with 8.0 wt % Fe3O4@NC, which can completely shield a 5G signal in a mobile phone. In addition, theory calculation reveals that there is a strongest dx2-Pz orbital hybridization interaction between Fe3O4 clusters and pyridinic-N dopants in the carbon network, compared with other kinds of N dopants, which can not only generate more dipoles of carbon networks but also increase net magnetic moments of Fe3O4, thereby leading to a coupling effect of efficient dielectric and magnetic losses. This work provides new insights into the precise design and synthesis of carbon-based magnetic composites with specific interface interactions and morphological effects for high-efficiency EMW absorption materials.

In situ loading of ZnO on hierarchical porous carbon derived from banana-peel waste to enrich mechanism for microwave absorption

Biomass has received widespread attention due to its easy availability, low cost, and environmental friendliness as an electromagnetic wave absorber candidate. Inspired by the natural porosity of biomass, the three-dimensional (3D) porous carbon materials derived from banana peels were prepared via coordination and pyrolysis carbonization. A conductive network of biomass-zinc complexes was constructed by introducing Zn2+ to coordinate with organic polymers. Hierarchical porous carbon/ZnO composites with a 3D skeleton network were obtained, which demonstrated outstanding electromagnetic wave absorption performance with an effective absorption bandwidth (EAB) of 6.72 GHz and the reflection loss (RL) of −44.18 dB. The banana peel-derived porous carbon (BPC) embedded with ZnO particles brings about conductive loss and interface polarization, further enriching the microwave loss mechanisms. This work offers a fresh idea for creating a green, sustainable, and high-value functional carbon-based composite material.

Flexible and hydrophobic CoFe-LDH @Co MOF @biomass-derived carbon fabrics for effective near-infrared photothermal conversion and electromagnetic attenuation

Near-infrared (NIR) laser countermeasures firing systems and electromagnetic wave shielding are extremely important in military warfare. Herein, a series of biomass-derived carbon flexible textiles with NIR photothermal conversion and microwave absorption capabilities were created by pyrolysis at temperatures ranging from 700 to 1000 °C. A hydrothermal approach was employed to create 2D CoFe-layered double hydroxides (CoFe-LDH), whose positively charged characteristics were securely attached to the hydroxide clusters on the surface of cotton fibers via electrostatic interaction. Subsequently, the adjustable layer spacing of LDH provides ideal in situ growth sites for metal ions and organic ligands of Co MOF. CoFe-LDH@Co MOF@PDMS cotton-derived carbon textiles (CoFe@PCCF) were successfully made using high-temperature pyrolysis, annealed carbonization, and polydimethylsiloxane curing. The intrinsic light absorption of the interwoven and entangled carbon fibers, combined with the plasmonic resonance of its surface metal particles, promotes photothermal conversion of the material, reduces density, and increases absorption during multiple reflections of electromagnetic waves. Furthermore, its qualities can be optimized and modified by modifying parameters like as carbonization temperature and thickness. As a result, CoFe@PCCF-900 shows the minimum reflection loss (RLmin) of −23.03 dB at 1.6 mm thickness and an effective absorption bandwidth (EAB) of 4.53 GHz. The surface temperature of CoFe@PCCF-1000 reaches 74.5 ℃ after 3 seconds of NIR (980 nm, 200 mW) light, indicating quick and stable photothermal conversion. This work provides an opportunity for laser shooting and electromagnetic attenuation low-cost materials.

Reflective anomalous beam splitter (RABS) metasurface for millimeter-wave (mm-Wave) frequency

Metasurfaces have gained a considerable amount of interest in the past decade for their capabilities to manipulate electromagnetic (EM) waves in different manners. They have offered multiple functionalities in terms of wave control depending on the given application. In terms of wave control, particularly EM beam splitting, it can be challenging compared to the given literature review, to achieve a wide number of beam-splitting reflections and coverage for multiple incident angles simultaneously. In this paper, we focus on the design of a metasurface based on the methodology of high periodicity supercell design (5.76λ) and impedance modulation to achieve a various number of beam-splitting angles, while maintaining the same coverage at multiple incident angles for millimeter-wave (mm-Wave) frequencies. Following the generalized phase law of reflection alongside proper optimization of the surface impedance, the proposed reflective anomalous beam splitter (RABS) metasurface is designed to be polarization independent, and high reflection efficiency is achieved with a wave beam split into 11 different directions while operating for multiple incident angles simultaneously, making it a promising candidate to overcome challenges for various mm-Wave communication applications, especially in expanding 5G coverage in non-line of sight regions at a 28 GHz frequency band. The performance of the RABS metasurface is evaluated using both full-wave simulations and experimental measurements, which demonstrate its effectiveness in achieving 11 efficient reflective anomalous beams with a reflection efficiency of up to 96.65% and 97.36% in TE and TM modes at 28 GHz.

Super-resolution diffractive neural network for all-optical direction of arrival estimation beyond diffraction limits

Wireless sensing of the wave propagation direction from radio sources lays the foundation for communication, radar, navigation, etc. However, the existing signal processing paradigm for the direction of arrival estimation requires the radio frequency electronic circuit to demodulate and sample the multichannel baseband signals followed by a complicated computing process, which places the fundamental limit on its sensing speed and energy efficiency. Here, we propose the super-resolution diffractive neural networks (S-DNN) to process electromagnetic (EM) waves directly for the DOA estimation at the speed of light. The multilayer meta-structures of S-DNN generate super-oscillatory angular responses in local angular regions that can perform the all-optical DOA estimation with angular resolutions beyond the diffraction limit. The spatial-temporal multiplexing of passive and reconfigurable S-DNNs is utilized to achieve high-resolution DOA estimation over a wide field of view. The S-DNN is validated for the DOA estimation of multiple radio sources over 5 GHz frequency bandwidth with estimation latency over two to four orders of magnitude lower than the state-of-the-art commercial devices in principle. The results achieve the angular resolution over an order of magnitude, experimentally demonstrated with four times, higher than diffraction-limited resolution. We also apply S-DNN’s edge computing capability, assisted by reconfigurable intelligent surfaces, for extremely low-latency integrated sensing and communication with low power consumption. Our work is a significant step towards utilizing photonic computing processors to facilitate various wireless sensing and communication tasks with advantages in both computing paradigms and performance over electronic computing.

Quadrupole mode plasmon resonance enabled dual-band metamaterial for refractive index sensing application

In this paper, design and fabrication of a dual-band near-zero index metamaterial (MTM) structure using copper on an epoxy resin fiber (FR-4) dielectric substrate is reported for refractive index sensing applications. The primary objective is to achieve dual-band operation spanning a 1–15 GHz frequency range, with a specific focus on achieving a broad bandwidth in the C-band. The resonance of the MTM structure was ascribed to the coupling of plane electromagnetic waves with surface plasmon polaritons on the structure, resulting in a quadrupole plasmon resonance mode. Furthermore, transmission characteristics of the fabricated MTM structure were experimentally measured and found to align closely with the simulated results obtained through the finite element method in COMSOL Multiphysics. The designed MTM structure demonstrates negative and near-zero permittivity at resonance frequencies, enabling left-handed and near-zero index behavior in dual microwave frequency bands. Under room temperature conditions, the MTM sensor exhibited sensitivities of 1 GHz/RIU and 3 GHz/RIU at resonance frequencies of 2.7 and 7.3 GHz, respectively. Consequently, the MTM structure exhibits significant potential for diverse applications, serving as a valuable component in sensors, detectors, and optoelectronic devices operating in the GHz region.

Transport properties of electromagnetic waves in dielectric photonic quasicrystals

Transport properties of electromagnetic waves in dielectric photonic quasicrystals

Cold plasma in wound healing

Even today, not all wounds can be healed. Treatment, which often takes many years, is a burden for patients and is very cost-intensive. Therefore, additional procedures such as cold plasma are becoming increasingly popular. Active components of cold plasma include electromagnetic radiation and free radicals. The active principle is based on, among other things, damage to bacterial cells and positive interaction with epithelial and endothelial cells. Angiogenesis and cellular oxygen metabolism are stimulated. The evidence base is still limited and heterogeneous, as some results are contradictory and comparability is difficult. However, new, well-designed studies have confirmed previous findings. In order to create a solid database, further studies are needed.

WHO to build neglect of RF-EMF exposure hazards on flawed EHC reviews? Case study demonstrates how "no hazards" conclusion is drawn from data showing hazards.

We examined one of the first published of the several systematic reviews being part of WHO's renewed initiative to assess the evidence of associations between man-made radiofrequency electromagnetic radiation (RF-EMF) and adverse health effects in humans. The examined review addresses experimental studies of pregnancy and birth outcomes in non-human mammals. The review claims that the analyzed data did not provide conclusions certain enough to inform decisions at a regulatory level. Our objective was to assess the quality of this systematic review and evaluate the relevance of its conclusions to pregnant women and their offspring. The quality and relevance were checked on the review's own premises: e.g., we did not question the selection of papers, nor the chosen statistical methods. While the WHO systematic review presents itself as thorough, scientific, and relevant to human health, we identified numerous issues rendering the WHO review irrelevant and severely flawed. All flaws found skew the results in support of the review's conclusion that there is no conclusive evidence for nonthermal effects. We show that the underlying data, when relevant studies are cited correctly, support the opposite conclusion: There are clear indications of detrimental nonthermal effects from RF-EMF exposure. The many identified flaws uncover a pattern of systematic skewedness aiming for uncertainty hidden behind complex scientific rigor. The skewed methodology and low quality of this review is highly concerning, as it threatens to undermine the trustworthiness and professionalism of the WHO in the area of human health hazards from man-made RF-EMF.

Neutrinos, light, matter, and the unification of gravitational and nuclear forces

Neutrinos, light, matter, and the unification of gravitational and nuclear forces The discovery of neutrinos and the measurement of their masses are significant events in the history of science. The Rotating Lepton Model provides a useful basis for understanding particles and nuclear reactions, highlighting the importance of Special Relativity, Gravity, and Quantum Mechanics in our universe. Professor Constantinos G. Vayenas explains. The discovery of neutrinos by Pauli some 90 years ago and the measurement of their masses by Kajita and McDonald (1) some 20 years ago constitute significant developments in the history of science. The recent (2023) (2) detection of neutrino production during the proton-proton collision experiments at CERN confirms the basic assumption of the Rotating Lepton Model (RLM) (2020), (3) i.e. that protons and neutrons comprise rotating neutrino triads, the former with a central positron. This implies that all matter in our Universe, including electromagnetic radiation, (4) comprises only five elementary particles: The three neutrinos (ν1, ν2, and ν3), the electron, and the positron. It also implies that two forces (gravity and electromagnetism) suffice for describing the interactions between these five particles and the concomitant production of all other composite particles, such as hadrons and bosons.

Multicomponent nonlinear fractional Schrödinger equation: On the study of optical wave propagation in the fiber optics

In this article, we investigate the soliton wave dynamics of the fractional three-component coupled nonlinear Schrödinger equation. This equation is considered as a fundamental tool for describing the behavior of optical pulses in optical fibers. There is increasing interest in studying these equations as they can be used to explain a wide range of complex physical phenomena in various scientific and engineering fields, including nonlinear fiber optics, electromagnetic field waves, and signal processing through optical fibers. In order to obtain the required solutions, the first step is to apply the complex wave transformations with β-fractional derivative to obtain the nonlinear ordinary differential equations of the governing model. Furthermore, by applying the novel integration methods known as generalized Arnous method and multivariate generalized exponential rational integral function approach, different type of soliton solutions are extracted. Different sets and values of the physical parameters are used to study the optical soliton solutions of the studied system. Based on a comparative analysis of our results with existing techniques, this study concludes that our proposed solutions are novel. The results described in this work are able to enhance the nonlinear dynamical behavior of a given system and confirm the effectiveness of the methods used. Furthermore, the different graphs are sketched to visualize the solutions behavior with various parametric values. It is anticipated that obtained solutions will be significant in the study of wave propagation and other related fields.

Circularly polarized beam-scanning leaky wave antenna based on a slow-wave substrate integrated waveguide

A circularly polarized (CP) beam-scanning leaky wave antenna (LWA) based on a slow-wave substrate integrated waveguide (SW-SIW) is presented in this paper. The SW effect is realized by introducing a spoof surface plasmon polariton (SSPP), excited by periodic etched 45° tilted slots on the top metallic layer of an SIW. With extra delta modulation, the electromagnetic waves radiate through the etched slots and scan continuously from a backward to forward direction as the frequency changes. Taking advantage of the tilted slots and relative displacement between the upper and lower slots, the direction of the electric field of the radiated waves and phase difference between them are adjustable, making a CP characteristic available. Both the simulated and measured results show the proposed LWA exhibits good performance. The total scanning angle reaches 70°, and the average gain is 8.9 dBi from 9.5 GHz to 11.7 GHz. The CP characteristic is verified through the axial ratio of less than 3 during the operating frequency range. A simple structure, compact size, and good performance make the proposed design promising for a compact wireless communication system.

Dynamics of fractional solitonic profiles to multicomponent Gross–Pitaevskii system

The fractional multicomponent Gross-Pitaevskii system arising in the Bose-Einestein condensate is under consideration. The Gross-Pitaevskii equation plays a significant role in Bose-Einstein condensation and engineering, where it characterizes the dynamics of the condensate wave function. Superfluidity and superconductivity are two characteristics of the low-temperature phenomenon that are linked to the Bose–Einstein condensate, which is generated by a diluted atomic gas. The investigation of multi-component equations has garnered considerable attention because of their capacity to clarify intricate physical phenomena and reveal the dynamic configurations of localized wave solutions. A variety of solutions have been secured in various forms, including bright, dark, singular, and combo solitons, in addition to solutions of hyperbolic, periodic, and exponential functions. For the purpose of ensuring the solutions, recently developed integration tools called the modified Sardar subequation method and enhanced modified extended tanh-expansion method have been implemented. In nonlinear dispersive media, solitons are stretched electromagnetic waves that maintain their intensity due to a balance between the effects of dispersion and nonlinearity. The proposed approaches are certainly the most direct, efficient, and valuable method for dealing with multiple nonlinear models that arise in applied physics and mathematics, with the purpose of generating various types of exact solutions. In addition, 3D, 2D, contour, and density plots have been utilized to visually represent the obtained results, facilitating a greater understanding of the physical effects of the derived solutions. The solutions attained are of great importance with regard to their applicability across a wide range of quantum systems.

Absorption-dominant electromagnetic interference shielding material using MXene-coated polyvinylidene fluoride foam

MXene (Ti3C2Tx), known for its exceptional electrical conductivity, unique two-dimensional structure, extensive surface functionality, and hydrophilicity, has emerged as a leading candidate for electromagnetic interference (EMI) shielding applications. Despite these excellent characteristics, EMI shielding materials based on MXene mostly utilize the reflection mechanism, which may cause secondary interferences. This study introduces an approach to utilize MXene as absorption-dominant EMI shielding materials. By engineering a porous layer of polyvinylidene fluoride (PVDF) atop MXene nanoflakes, we achieved a synergistic enhancement in EMI shielding effectiveness (SE) and absorptivity. The PVDF foam serves as an effective impedance matching layer, substantially enhancing the absorption of electromagnetic waves into the shielding material. Incorporating electrically conductive MXene nanoflakes to form a thin film creates a robust conductive network, fully leveraging its inherent performance. This network efficiently dissipates EM waves, thereby significantly enhancing the EMI SE. The shielding performance of this composite was thoroughly evaluated across both the X-band (8.2 GHz–12.4 GHz) and the Ka-band (26.5 GHz–40 GHz) frequencies. It demonstrated high EMI SE, attributed to mechanisms predominantly based on absorption. Specifically, it achieved an EMI SE of approximately 63.3 dB with high absorptivity (0.74) in the X-band and approximately 73.3 dB with high absorptivity (0.85) in the Ka-band. These findings underscore its potential as a route to develop absorption-dominant EMI shielding materials.

The problem of protecting a person from the effects of low-frequency electromagnetic fields in modern society. Possible ways to solve it

The paper considers the problem of the impact of low-frequency electromagnetic fields (EMF) generated by electric vehicles (EV) and household appliances on humans in modern society. The data on the effect of EMF on human health and regulatory documents establishing requirements for electromagnetic safety are presented. The method of electromagnetic shielding and materials for the implementation of this method are considered as a promising method for solving the problem. The levels of electromagnetic radiation from a number of EV and household electrical appliances have been experimentally measured. The efficiency of electromagnetic shielding of materials based on single-layer coatings of Ni80Fe20 alloys, multilayer film structures Ni80Fe20/Cu and amorphous metal alloys AMAG172 has been estimated using a computational method. It is shown that electromagnetic screens based on these materials significantly reduce the levels of exposure to EMF of EV and household electrical appliances on humans, which allows us to approach the hygienic standards recommended by doctors and meet the requirements of regulatory documents on remote control.

Synthesis of flexible magneto‐electric polyvinyl alcohol composites using hybrid filler particles of carbon quantum dots and cobalt nano for electromagnetic interference shielding application

AbstractThe main objective of the study is to synthesis and characterization of flexible magneto‐electric Polyvinyl Alcohol (PVA) composites for Electromagnetic Interference (EMI) shielding applications, by incorporating carbon quantum dots extracted from lychee fruit husks and cobalt nanoparticles sourced from Plectranthus amboinicus. Comprehensive mechanical, dielectrical, magnetic, and shielding tests were conducted to assess the performance of these novel materials. The mechanical characteristics of the composites were assessed to gauge their flexibility and robustness. In this regard, PV4 displayed a substantial tensile strength of 68 MPa, while PV6 exhibited an enhanced shore‐D hardness rating of 47. PV6 demonstrates superior dielectric properties, including a higher dielectric constant and a lower loss tangent, which are crucial for optimizing EMI shielding efficiency. When it comes to magnetic characteristics such as magnetization, retentivity, and coercivity, the PV6 composite designation outperforms the other composites. Additionally, PV6 exhibits higher electromagnetic interference (EMI) shielding effectiveness, measuring at approximately 49.8 dB in the E band and 56.5 dB in the F band. Findings demonstrate that the integration of carbon quantum dots and cobalt nanoparticles into the matrix resulted in flexible composites with enhanced mechanical strength. The incorporation of cobalt contributed to notable magnetic properties, increasing the materials' magnetization and retentivity. The tests on electromagnetic interference (EMI) showed that the shielding effectiveness got improved. The composite materials were able to reduce interference from electromagnetic waves in the tested frequency ranges. These flexible magneto‐electric PVA composites, developed using sustainable sources such as lychee fruit husks and Plectranthus amboinicus, exhibit promising potential for EMI shielding applications in diverse industries, including telecommunications, aerospace, and electronics, where reliable interference control is essential for optimal performance and safety.Highlights Cobalt nanoparticles sourced from Plectranthus amboinicus. Carbon quantum dots are prepared from lychee fruit husks via controlled pyrolysis. High tensile strength PVA composites prepared. Highest dielectric constant of 8.2 achieved for composite PV6. Higher wave shielding up to 56.5 dB achieved in “E” band.

Peltier effect of phonons driven by electromagnetic waves

Peltier effect of phonons driven by electromagnetic waves

Broadband microwave absorption and antibiosis effect of Cu@C@Fe3O4 nanocomposites

Metal Cu nanoparticles have been recognized as the long-standing presence in the fields of antibacterial and low-induced bacterial resistance, however, the uncontrollable Cu ion concentration from Cu nanoparticle leads to the unstable release of copper ions, limiting their controllable antibacterial application. Based on stable release of copper ions from Cu@C nanocapsules, herein, we report a novel A/B/C structure Cu@C@Fe3O4 nanocomposite to present integrated functionalities of highly controllable antibiosis and electromagnetic wave (EMW) absorption to realize a bifunctional EMW absorption system. With stable concentration, the Cu@C@Fe3O4 nanocomposite can slowly release Cu ions to experience an efficient reactive oxygen species process to realize extreme stable antibiosis behavior and long-term antibacterial effect that is 100 % bactericidal effect. With the sustained antibacterial conditions, the Cu@C@Fe3O4 with magnetic component simultaneously exhibits a good impedance matching to lead a broad microwave absorption with a bandwidth of 5.87 GHz. Considering above two functions, the multifunctional Cu@C@Fe3O4 provides a pathway for multifunctional EMW absorption materials exploration in antibacterial and microwave absorption applications. This strategy also indicates the possibility to functionalize magnetic nanocapsules towards even broader applications.