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Plasmonic Metasurfaces with Tunable Gap and Collective SPR Modes
摘要： Optical properties of a plasmonic metasurface made of a monolayer of gold nanoparticles in close proximity to an aluminum thin film were studied numerically and experimentally. Extinction spectra of the plasmonic metasurface were studied as functions of the thickness of a dielectric spacer between the monolayer of gold nanoparticles and the aluminum film in the visible wavelength range. The goal was to understand the excitation of a collective surface plasmon resonance (SPR) mode and a gap plasmon mode as well as their dependence on the spacer thickness, nanoparticles spacing and their size. By using finite-difference-time-domain (FDTD) calculations we find that the SPR extinction peak first red-shifts and then splits into two peaks. The first extinction peak is associated with the collective SPR mode of the monolayer and it shifts to shorter wavelengths as the spacer layer decreases. As the spacer layer decreases from 35 nm to 7.5 nm, the second peak gradually appears in the extinction spectra of the metasurface. We assign the second peak to the gap mode. The gap mode first appears at around 620 nm or greater and it shifts to larger wavelength for larger nanoparticle spacing and size. The FDTD simulations are confirmed by an experimental examination of the dispersion curves of a similar multilayer system. The computational results match the experimental results and confirm the excitation of the two modes.
关键词： gap plasmon mode,surface plasmon resonance,Plasmonic metasurfaces,aluminum thin film,FDTD,gold nanoparticles
更新于2025-11-19 16:56:42
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[IEEE 2018 IEEE International Conference on Computational Electromagnetics (ICCEM) - Chengdu (2018.3.26-2018.3.28)] 2018 IEEE International Conference on Computational Electromagnetics (ICCEM) - The HIE-FDTD Method for Simulating Graphene
摘要： The hybrid implicit-explicit finite-difference time domain (HIE-FDTD) method is presented to simulate the graphene layer. By using the auxiliary differential equation (ADE) and Pade fitting method, both the interband and intraband conductivity of the graphene are incorporated into the HIE-FDTD method. The time step increment in the proposed method is not determined by the fine meshes in the graphene layer, so the computational efficiency of this method is greatly improved from that of the conventional finite-difference time domain (FDTD) method, which is well validated by numerical examples. Besides, the numerical simulation also shows that the interband conductivity of the graphene has important effects on the performance of the graphene, especially at higher Terahertz (THz) spectra.
关键词： HIE-FDTD,graphene,FDTD
更新于2025-09-23 15:23:52
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Numerical study of nanoscale biosensor based on surface plasmon polariton propagation in Mach-Zehnder interferometer structure
摘要： In this paper, we numerically investigate a nanoscale plasmonic biosensor based on Mach-Zehnder interferometry. The operation of Mach-Zehnder interferometer (MZI) biosensor is examined based on two methods. In the first method, in which the transmission of surface plasmon polariton (SPP) modes is investigated under different refractive indices of sample medium as well as different dimensions, the best transmission rate achieved about 56.6% which is resulted by refractive index variation about 0.045 for the length 12 μm and width 80 nm of the gold layer. Also, the sensitivity, figure of merit (FOM) and quality factor (Q-factor) of MZI are examined for different geometries by utilizing the alternative method. It is realized that for the constant length, increasing the thickness of gold layer has significantly led to increased Q-factor and FOM. On the other hand, considering fixed thickness of the Au layer and three different lengths, the major outcome is that as the length of biosensor increases, the sensitivity, Q-factor as well as FOM follow an upward trend. Finally, inserting two distinct additional gold layers on top of the main gold layer, resulted in an extreme increase for the sensitivity and FOM of the plasmonic MZI biosensors with respect to the MZI biosensor without additional layer.
关键词： Plasmonic biosensor,Surface plasmon polariton (SPP),Mach-Zehnder interferometer (MZI),Finite difference time domain (FDTD)
更新于2025-09-23 15:23:52
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UPML-ABC of dispersive materials for the unconditionally stable 2-D WLP-FDTD method
摘要： In this paper, uniaxial anisotropic perfectly matched layer (UPML) absorbing boundary condition (ABC) of dispersive materials is presented for 2-D finite-difference time-domain (FDTD) method with weighted Laguerre polynomials (WLP). Taking advantage of the auxiliary differential equation (ADE) technique, our proposed algorithm avoids not only the complicated formulations but also the convolution integral. Using ADE scheme, the relationship between field components and auxiliary differential variables is derived in Laguerre domain. Substituting auxiliary differential variables into UPML-ABC, the electric field E of order q can be expressed directly by magnetic field H in Laguerre domain. Inserting magnetic field H of order q into electric field, and using central difference scheme, the formulations of uniaxial anisotropic dispersive media PML are obtained. One numerical example of wave propagation in 2-D dispersive materials is simulated. Numerical results validate the efficiency of the presented method.
关键词： finite-difference time-domain (FDTD),weighted laguerre polynomials (WLP),uniaxial anisotropic dispersive materials,perfectly matched layer (PML),Auxiliary differential equation (ADE)
更新于2025-09-23 15:23:52
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[IEEE 2018 3rd International Conference for Convergence in Technology (I2CT) - Pune (2018.4.6-2018.4.8)] 2018 3rd International Conference for Convergence in Technology (I2CT) - Implementation of Polarization-Conversion in Ring-Resonator and its Application to Design All-Optical NOT Logic Gate
摘要： All-optical NOT logic gate is theoretically described using the concept of polarization-conversion in ring resonator. Conversion of polarization states occurs at very high speed of 0.2 ps and high Q-factor of about 1500 is obtained. The design may used in intensity based all-optical switching as well as in designing of all-optical logic gates. Low pump power of about 40 nW/m is required for such conversion based all-optical gates. Suitability in pumping, refractive index contrast, height-to-width ratio of waveguide and phase-matching condition is necessary to obtain such results.
关键词： ring-resonator,polarization conversion,all-optical switch,FDTD simulation,logic gates
更新于2025-09-23 15:23:52
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Finite-Difference Time-Domain Modeling for Electromagnetic Wave Analysis of Human Voxel Model at Millimeter-Wave Frequencies
摘要： The finite-difference time-domain (FDTD) modeling of a human voxel model at millimeter-wave (mmWave) frequencies is presented. It is very important to develop the proper geometrical and electrical modeling of a human voxel model suitable for accurate electromagnetic (EM) analysis. Although there are many human phantom models available, their voxel resolution is too poor to use for the FDTD study of EM wave interaction with human tissues. In this paper, we develop a proper human voxel model suitable for mmWave FDTD analysis using the voxel resolution enhancement technique and the image smoothing technique. The former can improve the resolution of the human voxel model and the latter can alleviate staircasing boundaries of the human voxel model. Quadratic complex rational function is employed for the electrical modeling of human tissues in the frequency range of 6–100 GHz. Massage passing interface-based parallel processing is also applied to dramatically speed up FDTD calculations. Numerical examples are used to illustrate the validity of the mmWave FDTD simulator developed here for bio electromagnetics studies.
关键词： human tissue,electromagnetic wave,Doppler radar,dispersion model,bioelectromagnetics,Finite-difference time-domain (FDTD) method,parallel processing
更新于2025-09-23 15:23:52
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Comparison of the standard differencing with the exponential differencing for the FDTD method in lossy media
摘要： This paper compares the standard and exponential differencing's on time used with the FDTD method in such lossy media as conducting media and plasma media. It is shown that the performances of the two differencing's are quite close, concerning both the accuracy of the computed results and the domain of validity of the FDTD method in lossy media. There is no particular advantage nor drawback in using one differencing in place of the other, they can be used indifferently in FDTD calculations.
关键词： plasmas,conducting materials,FDTD methods
更新于2025-09-23 15:22:29
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[IEEE 2018 International conference on Computing, Electronic and Electrical Engineering (ICE Cube) - Quetta, Pakistan (2018.11.12-2018.11.13)] 2018 International Conference on Computing, Electronic and Electrical Engineering (ICE Cube) - Mathematical Modeling of Photonic Crystal based Optical Filters using Machine Learning
摘要： In this paper, we present a new approach to design photonic crystal based optical filters using machine learning based mathematical model. The presented optical filter device finds its application in near infrared spectral range. The design and spectral response of the filter can be predicted using the proposed mathematical model which can considerably reduce simulation time and efforts. The numerical simulation of the optical filter device along with its spectral results and mathematical modeling are described.
关键词： machine learning in optics,machine learning,optical filters,guided-mode resonance,Dielectric photonic crystals,low-index contrast,FDTD
更新于2025-09-23 15:22:29
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B-scan wave outline analysis in numerical modeling of ground-penetrating radar response from layered rough interfaces
摘要： Imaging of rough interfaces in a layered structure requires full understanding of the characteristics of their ground penetrating radar (GPR) echoes. In this study, a finite-difference time-domain computational model using a uniaxial perfectly matched layer boundary for GPR demining of layered rough interfaces is constructed. On the basis of this model, the numerical results of B-scan echoes from two-layered and three-layered rough interfaces with different degrees of roughness are obtained and compared with the profiles of corresponding rough surfaces. These results and comparisons highlight the relationship between the B-scan wave outlines and the profile of the layered rough interfaces. The effect of roughness of the interface on the B-scan echoes are analyzed, and the influence of the upper rough surface profile on the shape of the B-scan wave outline from the lower rough surface is discussed.
关键词： layered rough interfaces demining,finite-difference time-domain method (FDTD),ground penetrating radar (GPR),echo characteristic analysis
更新于2025-09-23 15:22:29
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A Theoretical Extension of AH FDTD Method and Applications in Various Physical Fields
摘要： In this paper we extended the Associated Hermite (AH) FDTD method theoretically and used it to analyze various physical fields, which are electromagnetic field, acoustic field and heat-transfer field. The AH differential transformation operator is developed theoretically as a basic element for setting a time-frequency bridge, where several common operators such as differential, second-order differential and integral linear operator, etc. on the concept of signal processing and analyzing can be expediently transformed, which leads to a unified and much simpler derivation to construct the previous AH FDTD formula. Therefore, it gives a reconsideration for AH FDTD to calculate a more general or even arbitrary liner physic field problems, which are focused on the commonly partial differential equations. Finally, based on the time-frequency bridge theory, we adopted several examples for verification from the formula derivation to numerical validation in electromagnetic field, acoustic field and heat-transfer field, respectively.
关键词： Acoustic,Heat-transfer,Associated Hermite,Finite difference time domain (FDTD)
更新于2025-09-23 15:22:29