Wave Electromagnetic Simulation Research Articles

Development of a flat cutoff probe covered with a dielectric layer for non-invasive plasma diagnostics

Abstract Herein, we investigated the effect of a dielectric film on the transmission spectrum of a bar-type flat cutoff probe (BCP). By conducting electromagnetic wave simulations, we found that placing a dielectric film with a thickness of 1 mm or less on the sensor did not affect the measurement of the BCP under thin sheath condition. However, a film thickness of 1 mm or more results in a low-frequency shift in the cutoff frequency. The shift in the cutoff frequency was related not only to the film thickness, but also to the dielectric constant of the film and sheath width, which could be understood through a circuit model of the BCP. The calculated results were experimentally validated using alumina plates of various thicknesses. Consequently, our findings demonstrate that measuring the electron density on a BCP is feasible even when a dielectric film is deposited, thereby improving the accuracy of the measurement.

The use of gold and magnetite-gold composite nanoparticles for the enhanced detection of Salmonella LT2 cells under photoacoustic flow cytometry

Photoacoustic flow cytometry (PAFC) is an emerging technology that has generated significant interest in several research fields, particularly in bacteremia. The application of functionalised nanoparticles like gold and iron oxide-gold complex (Fe3O4-Au) has been realised to enhance the photoacoustic (PA) detection of bacteria cells under PAFC systems. Inclusively, the bacteria cell concentrations are statistically quantified through the number of time-signal detection counts. This study uses a similar technique by using gold (Au) and magnetite-gold complex (Fe3O4-Au) nanoparticles in the PAFC system to improve the detection of Salmonella LT2 (SLT2) cells under 532 nm laser irradiation, resulting in over a 200 % increase. However, this study’s contribution comes from the post-processing and analysis of PA time signals after exposing various concentrations of SLT2 cells. Upon fast Fourier transform (FFT) analysis of time signals, a distinct peak frequency at 2.75 MHz was significantly attributed to SLT2 as its likely acoustic frequency fingerprint, even at its lowest concentrations (10 CFU/ml). Furthermore, an electromagnetic wave simulation (optical scattering and heat transfer in fluids) was employed to distinguish the PA and Photothermal contributions of the nanoparticles in the system. The resulting data consolidates the continuous wave transform (CWT) of the time signal, where 22.5 – 30 µs was strongly affiliated with PA, and 32–40 µs was that of the photo-thermal-acoustic effect—indicating that both signals can be used to detect and potentially confirm the eradication of SLT2 cells. Overall, magnetised Fe3O4-Au nanoparticles yielded more efficiency through its reproducible PA time signals with 0.84 standard deviations, and its 2.75 MHz frequency peak area matches most accurately with the SLT2 cell concentration by 97.3 %.

Research on extremely low frequency electromagnetic wave model and simulation in wellbore communication

Over recent years, as digitalization and intelligence in oil wellbore have increased, so have the stricter requirements for wireless communication technology in terms of distance, accuracy, and portability. As a result, it’s necessary to rely on more advanced and efficient wireless communication technologies to meet the industry’s needs. However, traditional communication technologies such as cables and optical fibers have inherent shortcomings in construction, data interpretation, and cost. ELF electromagnetic waves are an ideal solution for communication in complex wellbore conditions due to long-distance communication and strong penetration capabilities, making it a highly effective option. Based on the theory of network splitting, this paper establishes a polygonal multiple-delays uncertainty coupled complex network model of ELF electromagnetic waves propagating through the casing in layered media and designs a controller, including expressions for the intensity of the magnetic and electric fields in different directions, and the propagation and distribution characteristics in different media. We determined that the optimal transmitting frequency of ELF electromagnetic waves under general conditions is 12.7 Hz. Based on field experiments, we verified that ELF electromagnetic waves can enable wireless wellbore communication within 1500 m without relays. We also analyzed the impact of casing thread deformation on ELF electromagnetic wave propagation due to high-temperature and high-pressure environments. We used simulation experiments to solve the distribution relationship between the electric and magnetic fields of the solenoids through casing and strata, as well as the coupling coefficients between the transmitting and receiving solenoids, and explore how different transmitting frequencies affect the efficiency of signal propagation. Both theories and experiments have verified the correctness of the model, and have also demonstrated the reliability and continuity of using ELF electromagnetic waves to achieve wireless wellbore communication, which provides a theoretical basis and feasibility for subsequent engineering applications.

Integrated photonic fractional convolution accelerator

An integrated photonic circuit architecture to perform a modified-convolution operation based on the discrete fractional Fourier transform (DFrFT) is introduced. This is accomplished by utilizing two nonuniformly coupled waveguide lattices with equally spaced eigenmode spectra, the lengths of which are chosen so that the DFrFT and its inverse operations are achieved. A programmable modulator array is interlaced so that the required fractional convolution operation is performed. Numerical simulations demonstrate that the proposed architecture can effectively perform smoothing and edge detection tasks even for noisy input signals, which is further verified by electromagnetic wave simulations. Notably, mild lattice defects do not jeopardize the architecture performance, showing its resilience to manufacturing errors.

Continuous On‐Chip Synthesis of Ag Nanoparticles Assisted by Resonant Microwave Heating Using a Post‐Wall Waveguide

Microfluidics made of dimethylpolysiloxane were developed for chemical synthesis using microwave heating at 24.125 GHz, and microwave efficiency was enhanced by the microwave resonance effect. In addition, the device was fabricated using a mold created using a 3D printer to reduce production costs. The microchip structure comprised a post‐wall waveguide and a microchannel that passed through the waveguide. This post‐wall waveguide also comprises metal columns (post‐wall) instead of a conductor side wall, and easily introduces microchannels through the gaps between the metal columns. The waveguide length was adjusted to achieve a resonance frequency of 24 GHz using an electromagnetic wave simulation, assuming that the microchannel was filled with pure water. Microwaves with an input power of 4 W caused a maximum temperature increase of 93 °C; this result is ~10 °C higher than that of a microchip with non‐resonant structure. In this study, Ag nanoparticles were synthesized using a chemical reaction induced by microwave irradiation of a chip flow system. Owing to irradiating the mixing reagent with microwaves of an input power of 4 W while controlling the flow rate at 0.7 μl/min, the formation of Ag nanoparticles with an average particle size of ~19.2 ± 2.4 nm was demonstrated by absorbance measurements and dynamic light scattering. It is expected that microwave microfluidics enhanced by the resonance effect will substantialize nanoparticle synthesis and high‐efficiency automated chemical synthesis combined with multichemical unit operations. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

Research and simulation of electromagnetic wave absorbing performance for lightweight cement-based materials containing expanded polystyrene with different particle sizes and carbon black

The electromagnetic wave (EMW) absorbing performance of cement-based materials incorporating expanded polystyrene (EPS) with varying particle sizes is comprehensively studied through a combination of experimental and simulation methods. The addition of conductive carbon black (CB) to the cement matrix significantly increases the conductivity and dielectric constant, thereby improving the loss capacity. The frequency shift behavior of single and three-layer absorbing materials adheres to the effective medium theory and interference cancellation principle. The enhancement in overall EM parameters leads to a shift of the reflection loss (RL) peak towards lower frequencies. For three-layer materials, an increase in the thickness of absorbent layer proves beneficial for enhancing absorption performance. Simulations can effectively model cement-based materials by employing uniform material settings, with the size of EPS particles serving as the primary variable. The simulation results reveal that an increase in EPS particle size, in both single-layer and multi-layer materials, causes a shift of the RL peak towards lower frequencies. Additionally, analysis of electric field mode distribution and EM power loss density distribution indicates that scattering at the curved EPS interface alters the propagation direction of EMWs, increasing opportunities for loss inside the cement-based material. Moreover, the three-layer absorbing material, with a density ranging from 850 to 900 kg/m3 and compressive strength exceeding 4 MPa, is suitable for EMW absorption in building envelope structures. In conclusion, an increase in EPS particle size and CB content leads to a low-frequency shift of the RL absorption peak. This discovery not only provides an empirical foundation for the development of absorption materials tailored to specific frequency bands but also offers an efficient approach for repurposing waste EPS of diverse sizes. Furthermore, the grading of EPS with different particle sizes has important practical significance for increasing the content of EPS and preparing lightweight cement-based materials.

A novel high accuracy finite-difference time-domain method

The finite-difference time-domain (FDTD) method is widely used for numerical simulations of electromagnetic waves and acoustic waves. It is known, however, that the Courant condition is restricted in higher dimensions and with higher order differences in space. Although it is possible to relax the Courant condition by utilizing the third-degree difference in space, there remains a large anisotropy in the numerical dispersion at large Courant numbers. This study aims to reduce the anisotropy in the numerical dispersion and relax the Courant condition simultaneously. A new third-degree difference operator including the Laplacian is introduced to the time-development equations of FDTD(2,4) with second- and fourth-order accuracies. The present numerical simulations have demonstrated that numerical oscillations due to the anisotropic dispersion relation are reduced with the new operator.Graphical

Do Nanobubbles Exist in Pure Alcohol?

The existence of nanobubbles in pure water has been extensively debated in recent years, and it is speculated that nanobubbles may be ion-stabilized. However, nanobubbles in the alcohol-water mixture and pure alcohols are still controversial due to the lack of ions present in the alcohol system. This work tested the hypothesis that stable nanobubbles exist in pure alcohol. The ultrasound and oscillatory pressure fields are used to generate nanobubbles in pure alcohol. The size distribution, concentration, diameter, and scattering intensity of the nanobubbles were measured by nanoparticle tracking analysis. The light scattering method measures the zeta potential. The Mie scattering theory and electromagnetic wave simulation are utilized to estimate the refractive index (RI) of nanobubbles from the experimentally measured scattering light intensity. The average RI of the nanobubbles in pure alcohols produced by ultrasound and oscillating pressure fields was estimated to be 1.17 ± 0.03. Degassing the nanobubble sample reduces its concentration and increases its size. The average zeta potential of the nanobubbles in pure alcohol was measured to be -5 ± 0.9 mV. The mechanical stability model, which depends on force balance around a single nanobubble, also predicts the presence of nanobubbles in pure alcohol. The nanobubbles in higher-order alcohols were found to be marginally colloidally stable. In summary, both experimental and theoretical results suggest the existence of nanobubbles in pure alcohol.

Teaching Electromagnetic Wave Simulation: Applying Perfectly Matched Layer (PML) in Two-Dimensional Fields

Teaching Electromagnetic Wave Simulation: Applying Perfectly Matched Layer (PML) in Two-Dimensional Fields

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.

Highly Efficient Color Conversion of 3D Photonic Crystal Phosphor Films for Micro‐Light‐Emitting Diode Applications

The color conversion efficiency of phosphor films can be significantly improved by producing them in the shape of photonic crystals (PhCs). When light with photonic band‐edge wavelengths is incident on a PhCs phosphor film, the excitation photons are resonantly absorbed, enhancing the emission intensity. This study develops three‐dimensional PhC phosphor films based on self‐assembled inverse opal structures. PhC phosphors are constructed using a silk fibroin polymer and red organic fluorescent dyes (λpeak ≈ 610 nm) doped into it. The photonic structures are designed using electromagnetic wave simulations and photonic band structure analyses. The fabricated PhC phosphor films are integrated with blue micro‐light‐emitting diode (micro‐LED) chips (λpeak ≈ 452 nm), resulting in a color conversion efficiency increase of more than 1.5 times that of bulk phosphor films. Additionally, experiments are performed using various micro‐LED chips with a size of less than 100 μm. Overall, the results of this study demonstrate the potential of PhC phosphor films in future micro‐LED‐based devices and applications, including displays and communication systems.

Simulation of Electromagnetic Waves with Sinusoidal Pulses on Metal through the Finite Difference Time Domain (FDTD) Method

Understanding electromagnetic wave physical phenomena in three dimensions can be challenging. This research aims to create a model for how electromagnetic waves travel through a three-dimensional medium. One of the best ways to visualize this type of electromagnetic wave is Finite-Difference Time-Domain (FDTD). The simulation results revealed that the properties of the dielectric material and conductivity affect the shape of the sinusoidal pulse propagation, where the electromagnetic wave experiences reflection and transmission. The properties of the material influence the electric and magnetic fields in various ways, affecting the interaction between the transmitted and reflected waves. This interaction is influenced by several factors, such as permeability, and leads to either constructive or destructive interference.

Efficient post-processing of electromagnetic plane wave simulations to model arbitrary structured beams incident on axisymmetric structures

The study of an optical beam interacting with material structures is a fundamental of nanophotonics. Computational electromagnetic solvers facilitate the rapid calculation of the scattering from material structures with arbitrary geometry and complexity, but have limited efficiency when employing structured excitation fields. We have developed a post-processing method and package that can efficiently calculate the full three-dimensional electric and magnetic fields for any optical beam incident on a particle or structure with at least one axis of continuous rotational symmetry, called an axisymmetric body (such as a sphere, cylinder, cone, torus or surface). Provided an initial batch of plane wave simulations is computed, this open-source package combines data from computational electromagnetic solvers in a post-processing fashion using the angular spectrum representation to create arbitrarily structured beams, including vector vortex beams. Any and all possible incident beams can be generated from the initial batch of PWSs, without the need for further simulations. This allows for efficiently performing parameter sweeps such as changing the angle of illumination or translating the particle position relative to the beam, all in post-processing, with no need for additional time-consuming simulations. We demonstrate some applications by numerically calculating optical force and torque maps for a spherical plasmonic nanoparticle in a tightly focused Gaussian beam, a plasmonic nanocone in an azimuthally polarised beam and compute the fields of a non-paraxial Laguerre–Gaussian vortex beam reflecting on a multilayered surface. We believe this package, called BEAMS, is a valuable tool for rapidly quantifying electromagnetic systems that are beyond traditional analytical methods.

Simulation of Coherent Electromagnetic Waves in Wavelength Division Multiplexing (WDM) Transmission

This study analyzes the application of Wavelength Division Multiplexing (WDM) in fiber optic networks which aims to find the wavelength, WDM optical spectrum and modes, as well as the CPR estimated phase and modes. In this study WDM allows the simultaneous transmission of different data streams through a single optical fiber, using different wavelengths. This research was conducted using the python OptiCommPy module. This module is used to perform modeling of complex optical fiber transmission systems by considering the various parameters and disturbances involved in optical transmission. The results obtained from this study are that WDM networks can use full or limited wavelength conversion, depending on the wavelength conversion capability of each network node. Whereas multifiber networks use fiber pools between network nodes, and multifiber WDM networks can be implemented without or with full wavelength conversion. This research can be a guide for designing coherent electromagnetic waves in WDM transmissions using the OptiCommPy python module.

Ultra-Wideband Multi-Octave Planar Interconnect for Multi-Band THz Communications

An ultra-wideband (UWB) interconnect technology using indium phosphide (InP)-based transitions for coupling the output signals from terahertz (THz) photodiodes featuring coplanar waveguide (CPW) outputs to low-loss dielectric rod waveguides (DRWs) is presented. The motivation is to exploit the full bandwidth offered by THz photodiodes without limitations due to standard rectangular waveguide interfaces, e.g., for future high data rate THz communications. Full electromagnetic wave simulations are carried out to optimize the electrical performance of the proposed InP transitions in terms of operational bandwidth and coupling efficiency. The transitions are fabricated on 100-µm-thin InP and integrated with silicon (Si) DRWs. Experimental frequency domain characterizations demonstrate efficient THz signal coupling with a maximum coupling efficiency better than − 2 dB. The measured 3-dB and 6-dB operational bandwidths of 185 GHz and 280 GHz, respectively, prove the multi-octave ultra-wideband features of the developed interconnect technology. The 6-dB operational bandwidth covers all waveguide bands between WR-12 to WR-3, i.e., a frequency range between 60 and 340 GHz. In addition, the multi-octave performances of the fabricated interconnects were successfully exploited in proof-of-concept THz communication experiments. Using intermediate frequency orthogonal frequency division multiplexing (OFDM), THz communications are demonstrated for several frequency bands using the same interconnect. Considering soft-decision forward error correction, error-free transmission with data rates of 24 Gbps at 80 GHz and 8 Gbps at 310 GHz is achieved.

Research and simulation of three-layered lightweight cement-based electromagnetic wave absorbing composite containing expanded polystyrene and carbon black

Based on impedance gradient principle, a three-layered lightweight and broadband electromagnetic wave (EMW) absorbing cement-based composite is designed and prepared using expanded polystyrene (EPS) and carbon black (CB) as wave-transparent and absorbent medium, respectively. The three-layer absorber indicates excellent EMW absorbing properties in 1.1–18 GHz frequency range due to the good impedance matching and attenuation capacity. The minimum value of reflection loss (RL) is –49.6 dB with a 7 cm thickness and an effective absorbent bandwidth (RL < –20 dB) of 14.32 GHz can be achieved at a thickness of 8 cm. Furthermore, the idealized EPS-cement/CB structure model is established and simulated by finite element method in X-band. The propagation process of EMW is visual and greatly affected by EPS, and the electric field distribution presents a circular loop. Here the Smith chart can be used to analyze the impedance source of each circular loop at different frequencies. What’s more, the density of three-layered composites is between 170–250 kg/m3, meeting the requirements of lightweight, and the compressive strength of single-layer composite reaches about 0.65 MPa when the density is 350 kg/m3. Thus, the three-layer lightweight EPS-cement/CB composite is a promising EMW absorber with broadband absorption performance, which could be used for protecting buildings from electromagnetic interference.

Direct nano-imaging of light-matter interactions in nanoscale excitonic emitters

Strong light-matter interactions in localized nano-emitters placed near metallic mirrors have been widely reported via spectroscopic studies in the optical far-field. Here, we report a near-field nano-spectroscopic study of localized nanoscale emitters on a flat Au substrate. Using quasi 2-dimensional CdSe/CdxZn1-xS nanoplatelets, we observe directional propagation on the Au substrate of surface plasmon polaritons launched from the excitons of the nanoplatelets as wave-like fringe patterns in the near-field photoluminescence maps. These fringe patterns were confirmed via extensive electromagnetic wave simulations to be standing-waves formed between the tip and the edge-up assembled nano-emitters on the substrate plane. We further report that both light confinement and in-plane emission can be engineered by tuning the surrounding dielectric environment of the nanoplatelets. Our results lead to renewed understanding of in-plane, near-field electromagnetic signal transduction from the localized nano-emitters with profound implications in nano and quantum photonics as well as resonant optoelectronics.

8.56-GHz quasi-optical launcher system with incident-mode selectivity on the QUEST spherical tokamak

An 8.56-GHz quasi-optical launcher system with incident-mode selectivity was developed for non-inductive electron cyclotron (EC) plasma ramp-up and long-pulse sustainment, and effective bulk-electron heating on the Q-shu University experiment with steady-state spherical tokamak (QUEST). A novel polarization-selective system was proposed to conduct fundamental and second harmonic EC heating and current drive experiments with ordinary and extra-ordinary mode waves, respectively. Selectivity of the incident modes or polarizations was confirmed using the whole developed system at a low power level. A large-sized mirror launcher was developed to inject the beam whose size was as small as possible near the QUEST major radius. The designed mirror performance was checked using a three-dimensional electromagnetic-wave simulator and a low-power test. Ultimately, 0.15-m sized beams for both the two polarizations were successfully attained near the QUEST major radius, even in low-frequency applications with long propagation.

КОМП’ЮТЕРНЕ МОДЕЛЮВАННЯ РОЗСІЮВАННЯ Е-ПОЛЯРИЗОВАНИХ ХВИЛЬ НА ЕКРАНОВАНІЙ ПРЕДКАНТОРОВІЙ СИСТЕМІ РЕФЛЕКТОРІВ

Computer simulation of electromagnetic wave scattering on a shielded periodic reflector system, with a special period structure is considered. The electrodynamic reflective structure consists of a screen and a periodic system of strips. The cross-section of the strips is a system of segments formed by the principle of constructing a generalized Cantor set at each of the periods. Іt was used a mathematical model based on the reduction of the initial boundary value problems for the Helmholtz equation to systems of singular integral equations. The choice of this approach did not require analytical calculations when changing the number of lattice elements. Using this approach, it was not necessary to make changes to the computer implementation of the algorithm. The computer experiment has proved the possibility of applying the discrete singularities method computational scheme for the considered structure. It is proved that the structure constructed according to the proposed principle has the properties of broadband and multimode for the studied values of the structure parameters. In particular, for the studied structures, the resonance occurred when the wavenumber was changed from 0 to 50, with a significant increase in amplitude occurring at harmonics with numbers up to 40. This phenomenon led to a complex structure of the lines of the absolute values of the amplitude of the scattered electric field above the grating. The presence of small areas with an increase in the amplitude of the scattered field by a factor of 5-6 compared to the amplitude the incident electromagnetic wave was observed. These properties show practical interest in the use of this type of antennas to improve electronic camouflage and tactical radio communications. In the future, it is planned to conduct computer simulations for imperfectly conducting structures and compare the results with the numerical results for the ideal case discussed in this paper.

Two Dimensional Simulation of Electromagnetic Waves on Metal Materials Using the FDTD Method

It is challenging to picture the physical phenomenon known as electromagnetic wave simulation. The purpose of this work is to model the propagation of electromagnetic waves on a two-dimensional medium. FDTD is a method that is quite relevant to be used in visualizing electromagnetic waves. One can utilise Maxwell's equations to describe discrete electromagnetic waves having TM mode. The simulation is in the form of a Gaussian pulse with the magnetic field H and the electric field E having position and time domains, respectively. The proposed simulation conditions have considered the program's boundary conditions and numerical stability. The differential equation method methodology is used in the FDTD method. The simulation results show that the wave without PML is impeccably reflected, and with PML, the wave is reflected by the material utilized. Materials with high conductivity will make the waves decay and reduce their intensity. This research can be used in the investigation of materials and communication media innovation.