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Telecommunication wavelength confined Tamm plasmon structures containing InAs/GaAs quantum dot emitters at room temperature

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Physical Review B 2019年第16期100卷 165306-165306页

作者： Matthew Parker Edmund Harbord Lifeng Chen Edmund Clarke Kenneth Kennedy John Rarity Ruth Oulton Quantum Engineering Technology Laboratories H. H. Wills Physics Laboratory and Department of Electrical and Electronic Engineering University of Bristol Bristol BS8 1FD United Kingdom EPSRC National Epitaxy Facility University of Sheffield Centre for Nanoscience and Technology North Campus Broad Lane Sheffield S3 7HQ United Kingdom

We experimentally demonstrate gold microdisc structures that produce confined Tamm plasmons (CTPs)— interface modes between a metal layer and a distributed Bragg reflector— resonant around 1.3 μm. Quantum dots grown within the structures show an order of magnitude increase in the photoluminescence emitted at room temperature. Varying the disc diameter, we show spectral tuning of the resonance and measure the dispersion relation as evidence of mode confinement. The simplicity of fabrication and tuneability of these structures make CTPs an ideal platform for making scalable telecom devices based on quantum dots.

关键词： Plasmons III-V semiconductors Quantum dots Semiconductor microcavities Semiconductors finite-difference time-domain method

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Optical Bound States in the Continuum with Nanowire Geometric Superlattices

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Physical Review Letters 2019年第18期122卷 187402-187402页

作者： Seokhyoung Kim Kyoung-Ho Kim James F. Cahoon Department of Chemistry University of North Carolina at Chapel Hill Chapel Hill North Carolina 27599-3290 USA Department of Physics Chungbuk National University Cheongju 28644 Republic of Korea

Perfect trapping of light in a subwavelength cavity is a key goal in nanophotonics. Perfect trapping has been realized with optical bound states in the continuum (BIC) in waveguide arrays and photonic crystals; yet the formal requirement of infinite periodicity has limited the experimental realization to structures with macroscopic planar dimensions. We characterize BICs in a silicon nanowire (NW) geometric superlattice (GSL) that exhibits one-dimensional periodicity in a compact cylindrical geometry with a subwavelength diameter. We analyze the scattering behavior of NW GSLs by formulating temporal coupled mode theory to include Lorenz-Mie scattering, and we show that GSL-based BICs can trap electromagnetic energy for an infinite lifetime and exist over a broad range of geometric parameters. Using synthesized NW GSLs tens of microns in length and with variable pitch, we demonstrate the progressive spectral shift and disappearance of Fano resonances in experimental single-NW extinction spectra as a manifestation of BIC GSL modes.

关键词： Nanoantennas Nanophotonics Optical lattices & traps Optoelectronics Photonics Doped semiconductors Nanostructures Nanowires Semiconductors Single crystal materials Cavity resonators Crystal growth Electromagnetic wave theory Etching finite-difference time-domain method methods in electromagnetism Optical microscopy Scanning electron microscopy

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Polarization-dependent wide-angle color filter incorporating meta-dielectric nanostructures

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APPLIED OPTICS 2018年第14期57卷 3674-3678页

作者： Wu, Shangliang Ye, Yan Luo, Minghui Chen, Linsen Soochow Univ Coll Phys Optoelect & Energy Suzhou 215006 Peoples R China Soochow Univ Collaborat Innovat Ctr Suzhou Nano Sci & Technol Suzhou 215006 Peoples R China Soochow Univ Educ Minist China Key Lab Adv Opt Mfg Technol Jiangsu Prov Suzhou 215006 Peoples R China Soochow Univ Educ Minist China Key Lab Modern Opt Technol Suzhou 215006 Peoples R China

A metadielectric nanostructure with narrow cavities is proposed, behaving as a reflective color filter for TM-polarized light while as a broadband reflector for TE-polarized light. By varying the cavity depth or changing the incident light polarization, reflective colors of the proposed structure cover the entire visible spectrum conveniently. In particular, the reflections of this proposed structure show good angular tolerance up to 50 degrees for both polarizations. Furthermore, it can display colors even with two grating slits, which shows high printing resolution up to 70555 dpi, having great potential for applications of a large area color imaging and anticounterfeiting devices. (C) 2018 Optical Society of America.

关键词： Display technology Electron beam lithography finite-difference time-domain method Nanostructures Resolution Viewing angles

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Polarization-resolved edge states in terahertz topological photonic crystal

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Optics express 2019年第16期27卷 22819-22826页

作者： Hao Xiong Qiang Wu Yao Lu Ride Wang Qi Zhang Jiwei Qi Jianghong Yao Jingjun Xu The Key Laboratory of Weak-Light Nonlinear Photonics Ministry of Education TEDA Institute of Applied Physics and School of Physics Nankai University Tianjin 300457 China

The discovery of topological photonic states has revolutionized our understanding of electromagnetic propagation and scattering. With the introduction of topology, some attractive properties such as unidirectional propagation and robustness against defects and impurities will be endowed to photonic edge modes. In this study, two-dimensionally confined topological edge states were achieved at terahertz (THz) frequency based on an all-dielectric photonic crystal structure. Trivial and nontrivial bandgaps of two deforming honeycomb lattices as well as unidirectional topological edge states were observed. Because the topological edge states with opposite helicity propagated in opposite directions at the interface, a polarization-resolved characteristic was demonstrated here, and thus a continuously tunable power splitter was achieved. This study provides some insights for further THz topological studies and possibilities for THz integrated platforms.

关键词： Circular polarization Electromagnetic scattering finite-difference time-domain method Light sources Photonic crystals Wave propagation

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Nonreciprocal sound propagation in space-time modulated media

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Physical Review B 2019年第14期99卷 144311-144311页

作者： Junfei Li Chen Shen Xiaohui Zhu Yangbo Xie Steven A. Cummer Department of Electrical and Computer Engineering Duke University Durham North Carolina 27708 USA School of Mechatronics Engineering Harbin Institute of Technology Harbin 150001 China

Realization of nonreciprocal devices, such as isolators and circulators, is of fundamental importance in microwave and photonic communication systems. This can be achieved by breaking time-reversal symmetry in the system or exploiting nonlinearity and topological effects. However, exploration of nonreciprocal devices remains scarce in acoustic systems. In this work, sound propagation in a space-time modulated medium is theoretically studied. finite-difference time-domain simulations are carried out to verify the results. Functionalities such as mode conversion, parametric amplification, and phase conjugation are demonstrated.

关键词： Acoustics Sound waves Hydrodynamic waves Effective medium approach finite-difference time-domain method

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General framework for the frequency shifting of electromagnetic pulses using time-dependent surfaces

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Physical Review B 2019年第20期99卷 201407(R)-201407(R)页

作者： Hannah Pinson Vincent Ginis Applied Physics/Data Analytics Vrije Universiteit Brussel Pleinlaan 2 1050 Brussel Belgium Department of Physics Massachusetts Institute of Technology 77 Massachusetts Avenue Cambridge Massachusetts 02139 USA Harvard John A. Paulson School of Engineering and Applied Sciences Harvard University 29 Oxford Street Cambridge Massachusetts 02138 USA

Metasurfaces allow for agile manipulation of incoming light using a single layer of resonators. Despite recent progress, it remains difficult to generate new spectral components using nonlinear surfaces, because of the limited interaction length of a pulse traveling through a single surface. time-dependent surfaces offer an exciting alternative to overcome this limitation, but a self-consistent framework to describe this mechanism is lacking. Based on an analytical model and finite-difference time-domain numerical simulations, we obtain physical insight into the frequency-shifting process that occurs when broadband electromagnetic pulses interact with time-varying surfaces. In particular, we find that there is an intriguing relationship between the bandwidth of the incident pulse, the targeted frequency shift, and the number of Lorentzian resonators that need to be implemented. We also demonstrate that in certain parameter regimes, pulse distortion and a deviation of pulse amplitude cannot be avoided. These results are independent of the mechanism that generates the time dependence. They are also independent of the frequency, the geometry, size, and material of the unit cell, but they are rather a direct result of the subtle interplay between time-dependent Lorentzian resonances.

关键词： Electromagnetism Metamaterials Photonics Surfaces finite-difference time-domain method

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Instability of flux flow and production of vortex-antivortex pairs by current-driven Josephson vortices in layered superconductors

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Physical Review B 2019年第21期99卷 214512-214512页

作者： Ahmad Sheikhzada Alex Gurevich Department of Physics and Center for Accelerator Science Old Dominion University Norfolk Virginia 23529 USA

We report numerical simulations of the nonlinear dynamics of Josephson vortices driven by strong dc currents in layered superconductors. Dynamic equations for interlayer phase differences in a stack of coupled superconducting layers were solved to calculate a drag coefficient η(J) of the vortex as a function of the perpendicular dc current density J. It is shown that Cherenkov radiation produced by a moving vortex causes significant radiation drag increasing η(v) at high vortex velocities v and striking instabilities of driven Josephson vortices moving faster than a terminal velocity vc. The steady-state flux flow breaks down at v>vc as the vortex starts producing a cascade of expanding vortex-antivortex pairs evolving into either planar macrovortex structures or branching flux patterns propagating both along and across the layers. This vortex-antivortex pair production triggered by a rapidly moving vortex is most pronounced in a stack of underdamped planar junctions where it can occur at J>Js well below the interlayer Josephson critical current density. Both vc and Js were calculated as functions of the quasiparticle damping parameter, and the dc magnetic field was applied parallel to the layers. The effects of vortex interaction on the Cherenkov instability of moving vortex chains and lattices in annular stacks of Josephson junctions were considered. It is shown that a vortex driven by a current density J>Js in a multilayer of finite length excites self-sustained large-amplitude standing waves of magnetic flux, resulting in temporal oscillations of the total magnetic moment. We evaluated a contribution of this effect to the power W radiated by the sample and showed that W increases strongly as the number of layers increases. These mechanisms can result in nonlinearity of the c-axis electromagnetic response and contribute to THz radiation from the layered cuprates at high dc current densities flowing perpendicular to the ab planes.

关键词： Josephson effect Proximity effect Superconductivity Vortices in superconductors Collective dynamics High-temperature superconductors Josephson junctions Solitons Superconducting devices Superconductors finite-difference time-domain method methods in superconductivity

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Development of a wireless power transmission simulator based on finite-difference time-domain using graphics accelerators

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IET POWER ELECTRONICS 2017年第14期10卷 1889-1895页

作者： Ishida, Hiroki Furukawa, Hiroto Kyoden, Tomoaki Tanaka, Takahiro Okayama Univ Sci Dept Appl Phys Kita Ku 1-1 Ridai Cho Okayama 7000005 Japan Toyama Coll Natl Inst Technol Dept Elect & Control Syst Engn Toyama Japan Toyama Coll Natl Inst Technol Dept Maritime Technol Toyama Japan

We describe a method for simulating an electromagnetic induction type wireless power transmission (WPT) device. This simulator was based on the finite-difference, time-domain method. To reduce computation time, two graphics processing units (GPUs) were used as accelerators for the electromagnetic field computation. The first GPU calculated the electromagnetic field for the non-resonance state, and the second GPU calculated the field for the resonance state. Only two physical quantities needed to be exchanged between the two GPUs: self-inductance and the magnetic coupling coefficient. Capacitors and a load resistance were virtually connected to the coils as lumped elements. The experimental and simulation results were in good agreement. It is expected that a transient response analysis of WPT devices will become possible in the future using this simulation architecture.

关键词： inductive power transmission finite difference time-domain analysis graphics processing units computational electromagnetics radiofrequency power transmission wireless power transmission simulator finite-difference time-domain method graphics accelerators electromagnetic induction type wireless power transmission device simulation architecture WPT devices transient response analysis coils lumped elements load resistance capacitors self-inductance magnetic coupling coefficient nonresonance state electromagnetic field computation GPUs graphics processing units

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finite-difference time-domain modeling of monolayer graphene devices at near-infrared wavelengths

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JOURNAL OF NANOPHOTONICS 2017年第4期11卷 046008-1-046008-14页

作者： Davoodi, Fatemeh Granpayeh, Nosrat KN Toosi Univ Technol Ctr Excellence Electromagnet Opt Commun Lab Fac Elect Engn Tehran Iran

A finite-difference time-domain (FDTD) discretization of the dispersive conductivity of monolayer graphene has been done at the wavelength of 1.55 mu m, the third telecommunication window. The FDTD discretization is used to simulate a monolayer graphene plasmonic waveguide and a graphene surface plasmon polariton add-drop filter. We utilize the auxiliary equation method to solve Maxwell's equations in time-domain and simulate monolayer graphene-based devices without using the subcell method. The results show that the implementation of this method is surprisingly consistent with the results of the previous works and theoretical method. Our proposed method does not suffer from the deficiencies of the subcell and surface boundary condition methods. Both the interband and the intraband terms of the graphene conductivity are used to implement the graphene simulation. Our proposed method is useful for the analysis of monolayer graphene devices at near-infrared wavelengths with less computational complexity. (C) 2017 Society of Photo-Optical Instrumentation Engineers (SPIE)

关键词： optical waveguides add-drop filter graphene devices monolayer graphene finite-difference time-domain method graphene optical simulation near-infrared wavelengths

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Development and analysis of Crank-Nicolson scheme for metamaterial Maxwell's equations on nonuniform rectangular grids

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NUMERICAL methodS FOR PARTIAL DIFFERENTIAL EQUATIONS 2018年第6期34卷 2040-2059页

作者： Wang, Xiang Li, Jichun Fang, Zhiwei Nanchang Univ Dept Math Sci Nanchang Jiangxi Peoples R China Univ Nevada Dept Math Sci Las Vegas NV 89154 USA

In this paper, we develop a fully implicit scheme on staggered grids to solve the Maxwell's equations when Drude metamaterial is involved. Unconditional stability and optimal error estimate of the scheme are proved. Numerical results are provided to support the theoretical analysis, and used to demonstrate the applicability of the scheme to simulate the complicated backward wave propagation phenomenon occurring in metamaterials.

关键词： backward wave propagation finite-difference time-domain method Maxwell's equations metamaterial nonuniform rectangular mesh

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