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A High-Performance Plasmonic Nanosensor Based on an Elliptical Nanorod in an MIM Configuration

IEEE SENSORS JOURNAL 2018年第15期18卷 6145-6153页

作者： Yousuf, S. M. Enamul Hoque Sakib, Mashnoon Alam Islam, Md Zahurul Bangladesh Univ Engn & Technol Dept Elect & Elect Engn Dhaka 1205 Bangladesh

In this paper, we propose and numerically investigate a surface plasmon resonance-based nanophotonic biosensor structure providing an extremely high sensitivity and transmission efficiency with a high figure-of-merit (FOM). The sensor structure consists of a 1-D metalic grating, rectangular nanoslabs, and single elliptical nanorod (NR) in a metal-insulator-metal configuration. The spectral response of the proposed sensor is evaluated numerically by using the finite-difference-time-domain computation method for its operation in the near-infrared region of the spectrum. The results show strong enhancement and very high spectral sensitivity of the local electromagnetic fields near the tip of the NR. The performance parameters of the nanosensor are then optimized as a function of the shape, size, cavity length, and other parameters of the nanostructures. The optimized sensitivity of this device is found to be 1960 nm/RIU with a transmission efficiency of 82.30% and an FOM of 42.26, which are very promising as compared to those of the contemporary nanosensors. As a specific biosensing application, the proposed sensor device is numerically simulated with different concentrations of satellite tobacco mosaic virus (STMV) solutions and found to be capable of sensing the virus with extraordinary optical sensitivity up to 0.245 nm/(g/l) making the nanosensor sensitive even to the smallest of changes in concentrations of the STMV solutions. This highly sensitive nanosensor may have aspiring applications in biomedical and environmental sensing mechanisms and nanophotonic integrated circuits.

关键词： Surface plasmon resonance integrated plasmonics localized surface plasmon polaritons biosensor finite-difference time-domain method

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Spatially asymmetric transients of propagating exciton-polariton modes in a planar CdZnTe/CdMgTe guiding structure

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Physical Review B 2019年第15期100卷 155308-155308页

作者： J. Vondran F. Spitzer M. Bayer I. A. Akimov A. Trautmann M. Reichelt C. Meier N. Weber T. Meier R. André H. Mariette Université Grenoble Alpes CNRS Institut NEEL Grenoble 38000 France

We report on ultrafast time-resolved pump-probe studies in a CdZnTe/CdMgTe planar guiding structure covered with a metallic grating. The one-dimensional periodic gold structure allows for efficient coupling into the guiding layer for p-polarized 30 fs optical pulses with a large spectral bandwidth of about 60 nm. The resulting spectral width of optical pulses propagating inside the guiding layer corresponds to 20–30 nm. We demonstrate that the excitation of exciton-polariton modes in the guiding layer leads to a modulation of the optical response in the vicinity of the excitonic resonance. Spatially resolved pump-probe measurements show an asymmetric behavior in the optical response when the relative position of the pump and probe spots is varied on the scale of ten micrometers perpendicular to the metal ridges. This is attributed to the excitation of resonant and off-resonant exciton-polariton modes which propagate in opposite directions inside the guiding layer in accordance with their dispersion relations. Two main mechanisms are considered and evaluated, namely, Pauli blocking and excitation-induced dephasing, which are shown to be responsible for the pump-induced changes in the exciton absorption spectrum. While both of these processes lead to the generation of photoexcited carriers in the guiding layer, their impact on the optical properties (transmission and reflection) are different which leads to the asymmetric behavior of the spatially resolved transients.

关键词： Exciton polariton Excitons II-VI semiconductors Waveguides Femtosecond laser spectroscopy finite-difference time-domain method Many-body techniques Ultrafast pump-probe spectroscopy

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time-Division Parallel FDTD Algorithm

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IEEE PHOTONICS TECHNOLOGY LETTERS 2018年第24期30卷 2143-2146页

作者： Ohnuki, Shinichiro Ohnishi, Ryohei Wu, Di Yamaguchi, Takashi Nihon Univ Coll Sci & Technol Tokyo 1018308 Japan Tokyo Metropolitan Ind Technol Res Inst Tokyo 1350064 Japan

We propose a novel and efficient algorithm to parallelize the finite-difference time-domain method, where the observation period is divided into an arbitrary number of subsections, whose computation is distributed to corresponding computer nodes. The proposed algorithm roughly reduces the computational time to an nth fraction of the conventional algorithm, where n is the number of nodes for parallel computing, thus verifying its efficiency improvement.

关键词： Fast inverse Laplace transform finite-difference complex-frequency-domain method finite-difference time-domain method time-division parallel algorithm

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A refractive index sensor based on an analogy T shaped metal-insulator-metal waveguide

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OPTIK 2018年 172卷 1199-1204页

作者： Wang, Liu Zeng, Ya-Ping Wang, Zhi-Yong Xia, Xiong-Ping Liang, Qiu-Qun Guilin Univ Technol Coll Sci Guilin 541004 Peoples R China

A refractive index sensor based on plasmonics metal-insulator-metal (MIM) waveguide coupled with an analogy T shaped resonator is proposed. The analogy T shaped resonator consists of two perpendicular rectangle cavities. At visible light range, the transmission characteristics of the sensor are investigated by using the finite-difference time-domain (FDTD) method. The transmission spectrum exhibits a Fano resonance shape, which is caused by the interaction between the broadband and narrowband resonances of the two rectangle cavities. The refractive index sensing property is systematically studied with varied structural parameters and refractive indices. The result shows the maximum sensitivity of the sensor is 680 nm/RIU. The sensor may be potential applied in integrated of optical circuits.

关键词： Plasmonics Metal-insulator-metal waveguide Refractive index sensor finite-difference time-domain method

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Full-wave analysis of traveling pulses developed in a system of transmission lines with regularly spaced resonant-tunneling diodes

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INTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS 2018年第3期46卷 671-682页

作者： Narahara, Koichi Maezawa, Koichi Kanagawa Inst Technol Dept Elect & Elect Engn 1030 Shimoogino Atsugi Kanagawa 2430292 Japan Univ Toyama Grad Sch Sci & Engn 3190 Gofuku Toyama Toyama 9308555 Japan

In a system of transmission lines with regularly spaced resonant-tunneling diodes (RTDs), where several straight RTD lines are connected halfway to a closed RTD line, a pulse-shaped rotary traveling wave develops on the closed line by mutual synchronization of the oscillatory edge developed in each straight RTD line. The oscillating edge on each straight line is synchronized with the traveling pulse, such that the system has the potential to generate multiphase oscillatory signals in millimeter-wave frequencies. To examine the dynamics of traveling pulses at such high frequencies, the system is modeled in the framework of the finite-difference time-domain method. It is found that a traveling pulse develops in the closed RTD line synchronized with the oscillatory edges moving in the straight lines, assuming a microstrip structure for each RTD line. We then compare the results of the finite-difference time-domain calculation with those predicted by the transmission line theory with parameter values obtained by the quasi-transverse electromagnetic estimation. In addition, the RTD line that compactly confines the electromagnetic fields is shown to have the potential to generate multiphase oscillatory signals at submillimeter-wave frequencies.

关键词： finite-difference time-domain method multiphase oscillations nonlinear transmission lines resonant-tunneling diodes synchronization

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Numerical and experimental investigation on structure-borne sound transmission in multilayered concrete structures

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JOURNAL OF SOUND AND VIBRATION 2018年 413卷 1-25页

作者： Asakura, T. Toyoda, M. Miyajima, T. Tokyo Univ Sci 2641 Yamazaki Noda Chiba 2788510 Japan Kansai Univ 3-3-35 Yamate Cho Suita Osaka 5648680 Japan Shimizu Corp Inst Technol Koto Ku 3-4-17 Etchujima Tokyo 1358530 Japan

Environmental vibrations in cities are transmitted to buildings and propagate through the buildings via complex paths composed of the structural elements in the building, such as concrete slabs, beams, and columns. In this study, the transmission characteristics of such structure-borne sound in building structures composed of concrete were experimentally and numerically investigated. The vibration and radiated sound characteristics of a five-storey concrete structure obtained experimentally through an excitation test using the hammering method and numerically through wave-based numerical calculations are presented and compared. In this study, the finite-difference time-domain (FDTD) method, which treats the target structure as a composition of two-dimensional plate and one-dimensional beam elements to enable a low-cost calculation, is applied as a wave-based scheme. The propagation characteristics of the vibration and sound within the same floor and across different floors were investigated by considering various combinations of receiver and source points, and the structure-borne sound transmission characteristics of a concrete structure with frame elements are discussed. (C) 2017 Elsevier Ltd. All rights reserved.

关键词： finite-difference time-domain method Structure-borne sound Wave-based numerical analysis Vibration simulation

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An unconditionally stable technique for uncertainty assessment in random media based on the ADI scheme

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JOURNAL OF ELECTROMAGNETIC WAVES AND APPLICATIONS 2018年第6期32卷 671-684页

作者： Salis, Christos I. Zygiridis, Theodoros T. Univ Western Macedonia Dept Informat & Telecommun Engn Kozani Greece

Stochastic media problems present a severe impact on the properties of the electromagnetic fields that usually deterministic methods tend to overlook. In this paper, we present a finite-difference time-domain (FDTD) technique, which is free from time step restrictions and manages to efficiently calculate the statistics of the involved fields in one realization. The proposed algorithm is a variation of the Stochastic FDTD method and exhibits satisfactory outcomes in high density grids. Numerical results verify the validity of our scheme compared to other methods, such as the Stochastic FDTD and the Monte Carlo techniques.

关键词： finite-difference time-domain method ADI-FDTD technique stochastic FDTD technique stochastic ADI-FDTD scheme Monte Carlo techniques random media problems

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Effects of Meshed p-type Contact Structure on the Light Extraction Effect for Deep Ultraviolet Flip-Chip Light-Emitting Diodes

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NANOSCALE RESEARCH LETTERS 2019年第1期14卷 149页

作者： Zheng, Yuxin Zhang, Yonghui Zhang, Ji Sun, Ce Chu, Chunshuang Tian, Kangkai Zhang, Zi-Hui Bi, Wengang Hebei Univ Technol Sch Elect & Informat Engn Key Lab Elect Mat & Devices Tianjin 5340 Xiping Rd Tianjin 300401 Peoples R China

In this work, flip-chip AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs) with various meshed contact structures are systematically investigated via three-dimensional finite-difference time-domain (3D FDTD) method. It is observed that both transverse electric (TE)- and transverse magnetic (TM)-polarized light extraction efficiencies (LEEs) are sensitive to the spacing and inclined angle for the meshed structure. We also find that the LEE will not be increased when a large filling factor is adopted for the meshed structures, which is because of the competition among the p-GaN layer absorption, the Al metal plasmon resonant absorption, and the scattering effect by meshed structures. The very strong scattering effect occurring in the hybrid p-GaN nanorod/p-AlGaN truncated nanocone contacts can enormously enhance the LEE for both TE- and TM-polarized light, e.g., when the inclined angle is 30 degrees, the LEE for the TE- and TM-polarized light can be increased by similar to 5 times and similar to 24 times at the emission wavelength of 280nm, respectively.

关键词： Ultraviolet light-emitting diode Light extraction efficiency AlGaN finite-difference time-domain method p-type contact

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Theory and experiments of coherent photon coupling in semiconductor nanowire waveguides with quantum dot molecules

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Physical Review B 2019年第8期99卷 085311-085311页

作者： Chelsea Carlson Dan Dalacu Chris Gustin Sofiane Haffouz Xiaohua Wu Jean Lapointe Robin L. Williams Philip J. Poole Stephen Hughes Department of Physics Queen's University Kingston Ontario Canada K7L 3N6 National Research Council of Canada Ottawa Ontario Canada K1A 0R6

We present a quantum optics theory, numerical calculations, and experiments on coupled quantum dots in semiconductor nanowire waveguides. We first present an analytical Green function theory to compute the emitted spectra of two coupled quantum dots, treated as point dipoles, fully accounting for retardation effects, and demonstrate the signatures of coherent and incoherent coupling through a pronounced splitting of the uncoupled quantum dot resonances and modified spectral broadening. In the weak excitation regime, the classical Green functions used in models are verified and justified through full three-dimensional solutions of Maxwell equations for nanowire waveguides, specifically using finite-difference time-domain techniques, showing how both waveguide modes and near-field evanescent mode coupling is important. The theory exploits an ensemble-based quantum description, and an intuitive eigenmode-expansion-based Maxwell theory. We then demonstrate how the molecular resonances (in the presence of coupling) take on the form of bright and dark (or quasidark) resonances, and study how these depend on the excitation and detection conditions. To go beyond the weak excitation regime, we also introduce a quantum master-equation approach to model the nonlinear spectra from an increasing incoherent pump field, which shows the role of the pump field on the oscillator strengths and broadening of the molecular resonances, with and without pure dephasing. Next, we present experimental photoluminescence spectra for spatially separated quantum dot molecules (InAsP) in InP nanowires, which show clear signatures of pronounced splittings, although they also highlight additional mechanisms that are not accounted for in the dipole-dipole coupling model. Two different approaches are taken to control the spatial separation of the quantum dot molecules, and we discuss the advantages and disadvantages of each.

关键词： Nanophotonics Double quantum dots Nanowires finite-difference time-domain method Green's function methods Molecular beam epitaxy

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Optically Driven Collective Spin Excitations and Magnetization Dynamics in the Néel-type Skyrmion Host GaV4S8

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Physical Review Letters 2019年第10期122卷 107203-107203页

作者： P. Padmanabhan F. Sekiguchi R. B. Versteeg E. Slivina V. Tsurkan S. Bordács I. Kézsmárki P. H. M. van Loosdrecht Physics Institute II University of Cologne 50937 Cologne Germany Institute of Applied Physics MD 2028 Chisinau Republic of Moldova Experimental Physics V Center for Electronic Correlations and Magnetism University of Augsburg 86159 Augsburg Germany Department of Physics Budapest University of Technology and Economics and MTA-BME Lendület Magneto-optical Spectroscopy Research Group 1111 Budapest Hungary Hungarian Academy of Sciences Premium Postdoctoral Program 1051 Budapest Hungary

GaV4S8 is a multiferroic semiconductor hosting magnetic cycloid (Cyc) and Néel-type skyrmion lattice (SkL) phases with a broad region of thermal and magnetic stability. Here, we use time-resolved magneto-optical Kerr spectroscopy to show the coherent generation of collective spin excitations in the Cyc and SkL phases. Our micromagnetic simulations reveal that these are driven by an optically induced modulation of uniaxial anisotropy. Our results shed light on spin dynamics in anisotropic materials hosting skyrmions and pave a new pathway for the optical manipulation of their magnetic order.

关键词： Demagnetization Ferromagnetism Light-induced magnetic effects Magnetic anisotropy Magnetic texture Magneto-optical Kerr effect Skyrmions Ultrafast magnetization dynamics Face-centered cubic Magnetic semiconductors Multiferroics Narrow band gap systems Spinels Coherent control Femtosecond laser irradiation Femtosecond laser spectroscopy finite-difference time-domain method Landau-Lifschitz-Gilbert equation Magnetization measurements Optical pumping Ultrafast pump-probe spectroscopy

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