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Coupling finite elements and auxiliary sources for Maxwell's equations
摘要： The Multiple Multipole Program is a Trefftz method approximating the electromagnetic field in a domain filled with a homogeneous linear medium. MMP can easily handle unbounded domains; yet, it cannot accommodate inhomogeneous or nonlinear materials, situations well within the scope of the standard finite element method. We propose to couple FEM and MMP to model Maxwell's equations for materials with spatially varying properties in an unbounded domain. In some bounded parts of the domain, we use Nédélec's first family of curl-conforming elements; in the unbounded complement, multipole expansions. Several approaches are developed to couple both discretizations across the common interface: 1. Least-squares–based coupling using techniques from PDE-constrained optimization. 2. Multifield variational formulation in the spirit of mortar finite element methods. 3. Discontinuous Galerkin coupling between the FEM mesh and the single-entity MMP subdomain. 4. Coupling by tangential components traces. We study the convergence of these approaches in a series of numerical experiments.
关键词： Method of Auxiliary Sources,Multiple Multipole Program,Finite Element Method,Computational electromagnetics,Trefftz method
更新于2025-09-23 15:22:29
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High Sensitivity Photonic Crystal Fiber Refractive Index Sensor with Gold Coated Externally Based on Surface Plasmon Resonance
摘要： In this paper we propose a gold-plated photonic crystal fiber (PCF) refractive index sensor based on surface plasmon resonance (SPR), in which gold is coated on the external surface of PCF for easy fabrication and practical detection. The finite element method (FEM) is used for the performance analysis, and the numerical results show that the thickness of the gold film, the refractive index of the analyte, the radius of the air hole in the first layer, the second layer, and the central air hole can affect the sensing properties of the sensor. By optimizing the sensor structure, the maximum wavelength sensitivity can reach 11000 nm/RIU and the maximum amplitude sensitivity can reach 641 RIU?1. Due to its high sensitivity, the proposed sensor can be used for practical biological and chemical sensing.
关键词： sensor,surface plasmon resonance,refractive index,finite element method,Photonic crystal fiber
更新于2025-09-23 15:22:29
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Metal-insulator-metal nano square ring resonator for gas sensing applications
摘要： In this paper, three designs of Square Ring resonator (SRR) based on metal-insulator-metal (MIM) WG are reported. The transmission spectra and electric field distribution of the sensor structure are simulated using finite element method (FEM). The effect of structural parameters on the spectral characteristics and sensing performance are investigated comprehensively. The maximum achieved sensitivity and figure of merit of the sensor reached 1320 nm/RIU and 16.7, respectively. Due to the high performance and easy fabrication, this kind of plasmonic structures can find noteworthy applications in integrated optical circuits and on-chip nano-sensors.
关键词： refractive index sensor,square ring resonator,finite element method,Surface plasmon polariton,metal insulator metal waveguide
更新于2025-09-23 15:22:29
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Rectangular Lattice Photonic Crystal Fiber with Simultaneous Polarization Filtering at Communication Wavelengths of 1310 nm and 1550 nm
摘要： In this study, we developed a tunable photonic crystal fiber (PCF) polarized filter with a gold coating and liquid filling, which was investigated using the full-vector finite-element method. The gold that selectively filled the cladding air holes acted as a defect mode. When light was transmitted into the core, the energy was transferred from the core mode to the defect mode at a given wavelength and a resonance peak was obtained. Numerical results showed that the proposed PCF could be implemented simultaneously for polarization filtering in the communication windows of 1.31 and 1.55 μm. The confinement losses for the y-polarized mode were 251.5 dB/cm for 1.31 μm and 375.3 dB/cm for 1.55μm. When the fiber length was 90 μm, the corresponding bandwidths were just less than 20 and 70 nm for 1.31 and 1.55 μm, respectively. The bandwidths are the narrowest obtained and they are conducive to applications in integrated systems. We also studied the effects of structural parameters on the resonance performance. The optical fiber structure could be optimized further to obtain better results.
关键词： Photonic crystal fiber,Polarization filter,Full-vector finite element method
更新于2025-09-23 15:21:21
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A Domain Decomposition Finite Element Method for Modeling Electromagnetic Scattering from Rough Sea Surfaces with Emphasis on Near-Forward Scattering
摘要： A high fidelity full-wave simulator is presented to perform numerical experiments for rough sea scattering problem by considering different polarizations, frequencies, grazing angles, wind speeds and sea surface spectra. The simulator is based on a novel Finite Element Domain Decomposition (FEDD) method for solving the problem of two dimensional electromagnetic scattering over one-dimensional sea surface. This non-iterative method partitions the computational domain into a number of overlapping subdomains and solves each domain individually by employing the Locally-Conformal Perfectly Matched Layer (LC-PML) at the truncation boundaries. LC-PML has a unique feature such that it can be applied to irregular domains on the contrary to standard PML methods, and hence inspired the birth of FEDD. The FEDD method is used at each Monte Carlo realization corresponding to a sample from random rough surfaces, and decreases the computational load especially for electrically-large problems. The accuracy and computational efficiency of the method is investigated through several simulations. Using the FEDD method, the statistical behavior of the bistatic Radar Cross Section (RCS) is obtained for both horizontal and vertical polarizations. A special emphasis is given to forward-scattered RCS and the mean reflection coefficient for sea surface especially at low grazing angles, and it is shown that the simulator produces results in agreement with the Ament and Miller-Brown approximations, and experimental data, proving the reliability of the simulation approach. The results are also compared with the standard finite element method and method of moments. Rough sea surfaces are created by using both Pierson-Moskowitz and Elfouhaily spectra.
关键词： Locally-Conformal Perfectly Matched Layer (PML),forward scattering,sea surface,Domain decomposition,Monte Carlo,rough surface scattering,Finite Element Method (FEM),propagation,reflection coefficient,bistatic Radar Cross Section (RCS),multipath
更新于2025-09-23 15:21:21
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Polarization-independent hybrid plasmonic coupler based on T-shaped slot waveguide
摘要： In this paper, a novel polarization-independent hybrid plasmonic coupler based on a T-shaped slot waveguide is proposed and investigated by numerical simulations using the finite element method. The structure supports both the TE-polarized slot waveguide mode and the TM-polarized plasmonic mode, offering a greater possibility to achieve the polarization-independent operation. The simulation results show that with proper structural parameters, the waveguide coupler with high extinction ratios of 31.2 dB (TE) and 30 dB (TM) and low insertion losses of 0.38 dB (TE) and 2.04 dB (TM) can be achieved at a telecommunication wavelength of 1550 nm. An investigation of the influence of structural perturbations indicates that the proposed coupler also has a good tolerance to fabrication errors. The proposed structure has potential applications in the field of subwavelength integrated photonic circuits.
关键词： polarization-independent,hybrid plasmonic coupler,finite element method,T-shaped slot waveguide,photonic integrated circuits
更新于2025-09-23 15:21:01
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[IEEE 2020 8th International Electrical Engineering Congress (iEECON) - Chiang Mai, Thailand (2020.3.4-2020.3.6)] 2020 8th International Electrical Engineering Congress (iEECON) - Design and Performance Analysis of an Ultra-compact Nano-plasmonic Refractive Index Sensor
摘要： In this paper, a Dielectric-Metal-Dielectric (DMD) plasmonic waveguide coupled with a rectangular slot is proposed and analyzed numerically with the Finite Element Method (FEM) as a refractive index sensor. Different structural parameters are varied to obtain maximum sensitivity of the proposed structure. In this geometry, silver is used as the metal and it is surrounded by Material Under Sensing (MUS) which is dielectric in nature. The linear correlation between both the refractive index and the position of the transmission peaks is used for the detection of the materials. From this simpler geometry, maximum sensitivity is obtained to be 818 nm/RIU; RIU means Refractive Index Unit. Due to the ease in the nanoscale fabrication of the proposed simplistic structure, it can have potential applications in nanoscale optical devices and the nano chip sensors.
关键词： Finite Element Method,Surface Plasmon Polaritons (SPPs),Refractive Index Sensor
更新于2025-09-23 15:21:01
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Laser fabrication of structural bone: surface morphology and biomineralization assessment
摘要： The current work explores the surface morphology of the laser-ablated bone using Yb-fiber coupled Nd:YAG laser (λ = 1064 nm) in continuous wave mode. As the laser-ablated region contains physiochemically modified carbonized and nonstructural region, it becomes unknown material for the body. Thus, biomineralization on such a laser-ablated region was assessed by in vitro immersion test in noncellular simulated body fluid. The presence of hydroxyapatite was detected in the precipitated mineral product using scanning electron microscopy equipped with energy dispersive spectroscopy, and X-ray diffraction analysis. The effect of varying laser parameters on distribution of surface morphology features was identified and its corresponding effect on biomineralization was studied.
关键词： Laser-bone interaction,Surface morphology,Finite element method (FEM) modeling,Laser ablation
更新于2025-09-23 15:21:01
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Numerical Modeling of Acousto-Plasmonic Coupling in Metallic Nanoparticles
摘要： We describe a computational approach to study the acousto-plasmonic coupling in metallic nanoparticles. We use the high level multiphysics finite element software FreeFEM developed at Laboratoire Jacques-Louis Lions of Pierre and Marie Curie University (Paris). Our numerical method determines one after the other the acoustic modes of the nanoparticles and the modulation of the electromagnetic properties. The transfer of the deformed geometries between acoustic and electromagnetic simulations is realized by an update of the nodal coordinates situated at the boundary between the nanoparticle and its host medium, and using a mesh deformation algorithm based on radial basis function interpolation. Thus we theoretically investigate different coupling mechanisms between confined vibrations and surface plasmons: shape effect, electron density effect due to changes of the nanoparticle volume and inter-band transitions effect which is evaluated by the deformation potential mechanism.
关键词： acousto-plasmonic coupling,radial basis function interpolation,FreeFEM,finite element method,metallic nanoparticles
更新于2025-09-23 15:21:01
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Taguchi Grey Relationalapproach Foroptimizing Process Parameters of Laser Peeningontitanium Alloy to Induce Enhanced Compressive Stress Based on Finite Element Simulation
摘要： Laser Shock Peening (LSP) turned out the most efficient surface engineering process for advanced materials to induce beneficial deep compressive residual stress which helps in improving mechanical, fatigue properties and surface damage resistance. But, analyzing the non-uniform distribution of residual stresses in the treated sample with XRD is much time taking and costly process. This problem can be resolved with LSP finite element numerical simulation model which is feasible with the realistic experimental process. The FE model allows the user to control the laser parameters in order to achieve the optimal level of all controllable parameters. The present study is intended to analyze and optimize the influence of laser processing parameters assists in inducing the residual compressive stress with minimal surface deformation.A Ti6Al4V material model with Johnson-Cook’s visco-elastic-plastic material behaviour law is prepared for LSP simulation. And Gaussian pressure profile is utilized for uniform loading of the targeted zone for the proposed model. Taguchi Grey Relational Analysis (TGRA) with L27 orthogonal array is applied to LSP simulation, and the results were analyzed with consideration of multiple response measures. It is noted that surface deformation is increased with the rise in a number of laser shots and pressure pulse duration. Maximum compressive residual stresses are falling for higher levels of laser spot diameter, Laser spot overlap and Laser Power density. The correlation is observed between FE simulation and published results. The optimal set of process parameters are obtained for improving the LSP on Ti alloys.
关键词： Grey Relational Analysis (GRA),Taguchi Technique,Laser Shock Peening (LSP),Finite Element Method (FEM),Residual Stresses
更新于2025-09-23 15:21:01