Open accessJournal Article

# Anisotropic Multi-layer Elliptical Waveguides Incorporating Graphene Layers: A Novel Analytical Model

02 Mar 2021-arXiv: Optics-
Abstract: This article aims to propose a novel analytical model for anisotropic multi-layer elliptical structures incorporating graphene layers. The multi-layer structure is formed of various magnetic materials. An external magnetic bias has been applied in the axial direction. A graphene layer, with isotropic surface conductivity, has been sandwiched between two adjacent anisotropic materials. A novel matrix representation has been derived to find the propagation parameters of the multi-layer structure. Two exemplary important cases of the proposed general structure, as waveguides, have been investigated to show, first the validity of our proposed analytical model, and second, the richness of the general structure. The analytical and simulation results show an excellent agreement. A very large value of the figure of merit (FOM), e.g. FOM=110, is achieved for the second structure for the chemical potential and external magnetic bias of 0.9 ev and 1T, respectively. Our general structure and its analytical model can be exploited to design innovative THz devices such as absorbers, couplers, and cloaks.

Topics: Figure of merit (51%)
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7 results found

Open accessJournal Article
06 Jan 2021-Plasmonics
Abstract: This paper presents an analytical study of transverse-magnetic-polarized surface plasmon polaritons (SPPs) in nonlinear multi-layer structures containing graphene sheets. In the general structure, each graphene sheet has been sandwiched between two different nonlinear magnetic materials. To show the richness of the proposed general waveguide, two novel nonlinear structures have been introduced and investigated as special cases of the general structure. It will be shown that the propagation features of these structures can be tuned by changing the chemical potential of the graphene and the incident mode power. A large value of the effective index, i.e., $${n}_{\mathrm{eff}}=240$$ for the chemical potential of $${\mu }_{c}=0.2 ev$$ and the incident power of $$\alpha {\left|{H}_{y,0}\right|}^{2}=3$$ is obtained for the second structure at the frequency of 40 THz. The analytical results confirm that the integration of nonlinear magnetic materials with graphene sheets can control and enhance the propagating features and the self-focused of the field in the nonlinear layer. This integration gives more degrees of freedom to the designer to propose new THz components such as lasers and switches in the THz region.

Topics: , Graphene (51%)

11 Citations

Open accessJournal Article
04 Jul 2021-arXiv: Optics
Abstract: In this article, an analytical model is proposed for the study of Transverse-electric (TE) surface plasmon polaritons (SPPs) in nonlinear multi-layer graphene-based waveguides. Each graphene sheet has been located between two different Kerr-type layers. As special cases of the general, proposed structure, two new nonlinear graphene-based waveguides are introduced and investigated in this paper. The obtained results show that the propagation properties of these exemplary structures are adjustable via chemical potential and nonlinear coefficients. A large value of the effective index, i.e. neff=82 is obtained for the chemical potential of 0.15 ev and the nonlinear ratio of 0.8 for the second structure at the frequency of 61 THz. The presented study suggests a novel platform in graphene plasmonics, which can be used for the design of innovative THz devices.

Topics: , Graphene (55%)

10 Citations

Journal Article
01 Apr 2021-Optik
Abstract: This article proposes a novel three-port circulator with a triangular graphene-based post for the THz region This new circulator is formed by three 120° symmetrical metal-based waveguides The anisotropic feature for circulation is provided by magnetically-biased graphene in the triangular post The DC magnetic bias is applied in the z-direction The magnetized, triangular graphene sheet supports hybrid TM-TE plasmons To realize the proposed circulator, the structure has been simulated in COMSOL software In our simulation results, isolation of -40 dB with a transmission loss of -35 dB is obtained at the central frequency of 5 THz for a specific design The bandwidth of the simulated circulator is reported 725 % with respect to the isolation level of -15 dB It has been shown that the scattering parameters of the proposed circulator can be changed by altering the chemical potential of the graphene and DC magnetic bias, which makes this circulator a tunable device to be utilized in various plasmonic systems

Topics: Circulator (69%)

8 Citations

Open accessJournal Article
09 Mar 2021-arXiv: Optics
Abstract: We propose a novel analytical model for anisotropic multi-layer cylindrical structures containing graphene layers. The general structure is formed by an aperiodic repetition of a three-layer sub-structure, where a graphene layer, with an isotropic surface conductivity, has been sandwiched between two adjacent magnetic materials. An external magnetic bias has been applied in the axial direction. General matrix representation is obtained in our proposed analytical model to find the dispersion relation. The relation will be used to find the effective index of the structure and its other propagation parameters. Two special exemplary structures have been introduced and studied to show the richness of the proposed general structure regarding the related specific plasmonic wave phenomena and effects. A series of simulations have been conducted to demonstrate the noticeable wave-guiding properties of the structure in the 10-40 THz band. A very good agreement between the analytical and simulation results is observed. The proposed structure can be utilized to design novel plasmonic devices such as absorbers, modulators, plasmonic sensors and tunable antennas in the THz frequencies.

Topics: Graphene (51%), Surface conductivity (51%), Dispersion relation (50%)

7 Citations

Open accessPosted Content
15 Mar 2021-arXiv: Optics
Abstract: This paper aims to study the magneto-plasmons in an anisotropic graphene nano-waveguide with bigyrotropic cover and substrate. The substrate is backed by a perfect electromagnetic conductor (PEMC) layer, a general and ideal boundary, which can be transformed easily into the perfect electric conductor (PEC) or the perfect magnetic conductor (PMC) boundaries. The upper and bottom layers of the graphene sheet are made of different magnetic materials. The external magnetic field is applied perpendicularly to the structure surface, which can be provided by a permanent magnet placed underneath the ground plane. Hence, the graphene sheet has anisotropic conductivity tensor. A novel analytical model has been proposed for the general nano-waveguide to find its propagation properties. As special cases of the proposed general structure, two important new waveguides have been introduced and studied to show, first the richness of the proposed general nano-waveguide regarding the related specific plasmonic wave phenomena and effects, and second the validity and the high accuracy of the proposed model. The analytical and the simulation results are in an excellent agreement. It is shown that the modal properties of the proposed structure can be tuned effectively via the external magnetic field and the chemical potential of the graphene. Harnessing the non-reciprocity effect of anisotropic materials and the graphene sheet, the presented analytical model can be exploited to design tunable innovative devices in THz frequencies.

Topics: Perfect conductor (59%), Graphene (54%), Magnetic field (51%)

2 Citations

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56 results found

Open accessBook
30 Nov 1996-
Abstract: Isotropic Ferromagnet Magnetized to Saturation Ferromagnetism Elementary Magnetic Moments Paramagnetism Weiss Theory Exchange Interaction Equation of Motion of Magnetization High-Frequency Magnetic Susceptibility Solution of the Linearized Equation of Motion Peculiarities of the Susceptibility Tensor High-Frequency Permeability Allowance for Magnetic Losses Dissipative Terms and Dissipation Parameters Susceptibility Tensor Components Uniform Oscillations in a Small Ellipsoid Internal and External Magnetic Fields Eigenoscillations Forced Oscillations Anisotropic Ferromagnet Landau-Lifshitz Equation Generalization of Equation of Motion Methods of Analysis of Ferromagnetic Resonance in Anisotropic Ferromagnet Magnetocrystalline Anisotropy Origins of Magnetocrystalline Anisotropy Phenomenological Description Equilibrium Orientations of Magnetization Ferromagnetic Resonance in a Single Crystal Sphere of Uniaxial Ferromagnet Sphere of a Cubic Ferromagnet Simultaneous Allowance for Different Kinds of Anisotropy Ferromagnetic Resonance in a Polycrystal Independent-Grain and Strongly-Coupled Grain Approximations Influence of Porosity Antiferromagnets and Ferrites Antiferromagnetism and Ferrimagnetism Crystal and Magnetic Structures Equations of Motion and Energy Terms Ground States and Small Oscillations Antiferromagnetic Resonance Antiferromagnet with an Easy Axis of Anisotropy: Steady States Oscillations in Antiparallel State Oscillations in Noncollinear State Oscillations in Transverse and Arbitrarily Oriented Fields Antiferromagnet with Easy Plane of Anisotropy Magnetic Oscillations in Ferrimagnets Ground States of Two-Sublattice Ferrimagnet Oscillations in Antiparallel Ground State Oscillations in Noncollinear Ground State Damped and Forced Oscillations Fundamentals of Electrodynamics of Gyrotropic Media Equations General Equations and Boundary Conditions Equations for Bigyotropic Media Uniform Plane Waves General Relations Longitudinal Magnetization Transverse Magnetization Nonreciprocity Energy Relations Equation of Energy Balance Energy Losses Perturbation Method Gyrotropic Perturbation of a Waveguide Gyrotropic Perturbation of a Resonator Quasistatic Approximation Resonator with Walls of Real Metal Waveguides and Resonators with Gyrotropic Media. Microwave Ferrite Devices Waveguide with Longitudinally Magnetized Medium Circular Waveguide Circular Waveguide with Ferrite Rod Faraday Ferrite Devices Waveguide with Transversely Magnetized Ferrite Rectangular Waveguide Filled with Ferrite Rectangular Waveguide with Ferrite Plates Microwave Ferrite Devices Resonators with Gyrotropic Media Eigenoscillations and Forced Oscillations Waveguide Resonators Ferrite Resonators Use of Perturbation Method Waveguides and Waveguide Junctions with Ferrite Samples Ferrite Ellipsoid in a Waveguide Coupling of Orthogonal Waveguides. Ferrite Band-Pass Filters General Properties of Nonreciprocal Junctions Magnetostatic Waves and Oscillations Magnetostatic Approximation Nonexchange Magnetostatic Waves in Plates and Rods Volume Waves in Plates Surface Waves Magnetostatic Waves in Waveguides with Finite Cross Section Energy Flow and Losses Magnetostatic Waves in Ferrite Films: Excitation, Applications Magnetostatic Oscillations (Walker's Modes) Metallized Cylinder Sphere and Ellipsoid of Revolution Damping, Excitation, and Coupling Spin Waves Spin Waves in Unbounded Ferromagnet Energy and Effective Field of Exchange Interaction Dispersion Law Magnetization, Field Components, and Damping Spin Waves in Bounded Bodies Exchange Boundary Conditions Standing Spin Waves in Films Propagating Spin Waves in Films Spin Waves in Nonuniform Magnetic Fields Magnons Quantization of Magnetic Oscillations and Waves Thermal Magnons Elements of Microscopic Spin-Wave Theory Diagonalization of the Hamiltonian Discussion of the Dispersion Law Allowance for Dipole-Dipole Interaction and Anisotropy Interaction of Magnons Magnetic Oscillations and Waves in Unsaturated Ferromagnet Oscillations of Domain Walls Domain Walls and Domain Structures Equation of Motion of a Domain Wall Dynamic Susceptibility Ferromagnetic Resonance in Samples with Domain Structure Ellipsoid of Uniaxial Ferromagnet Sphere of Cubic Ferromagnet Nonuniform Modes in Unsaturated Samples Nonlinear Oscillations of Magnetization Ferromagnetic Resonance in Strong Alternating Fields Rigorous Solution of Equation of Motion Approximate Methods Harmonic Generation and Frequency Conversion Frequency Doubling Frequency Mixing Parametric Excitation of Magnetic Oscillations and Waves Nonlinear Coupling of Magnetic Modes Thresholds of Parametric Excitation under Transverse Pumping First-Order and Second-Order Instabilities Threshold Fields Effect of Pumping-Field Polarization Longitudinal and Oblique Pumping Longitudinal Pumping Effect of Nonuniformities Oblique Pumping Instability of Nonuniform Modes and Nonuniform Pumping Parametric Excitation of Magnetostatic Oscillations and Waves Ferrite Parametric Amplifier Nonuniform Pumping Above-Threshold State Reaction of Parametric Spin Waves on Pumping Phase Mechanism Nonlinear Damping Stability of the Above-Threshold State Nonlinear Microwave Ferrite Devices Spin-Spin Relaxation Relaxation Processes in Magnetically Ordered Substances Kinds of Relaxation Processes Methods of Theoretical Study Inherent Spin-Spin Processes Three-Magnon Splitting Three-Magnon Confluence Four-Magnon Scattering Inherent Processes for Uniform Precession Experimental Data Two-Magnon Processes Theory of Two-Magnon Processes Disorder in Distribution of Ions over Lattice Sites Anisotropy-Field Variation and Pores in Polycrystals Surface Roughness Magnetoelastic Coupling Elastic Properties and Magnetoelastic Interaction Elastic Waves and Oscillations Magnetoelastic Energy and Equations of Motion Effect of Elastic Stresses on Ferromagnetic Resonance Magnetoelastic Waves Normal Waves Damping and Excitation Magnetoelastic Waves in Nonuniform Steady Magnetic Field Parametric Excitation of Magnetoelastic Waves Longitudinal Pumping of Magnetoelastic Waves Parametric Excitation Caused by Magnetoelastic Coupling Elastic Pumping Spin-Lattice Relaxation Ionic Anisotropy and Relaxation Anisotropy Caused by Impurity Ions Energy Levels of Ions One-Ion Theory of Ferromagnetic-Resonance Anisotropy Near-Crossing Energy Levels Experimental Data Ion Relaxation Processes Transverse Relaxation Longitudinal (Slow) Relaxation Relaxation of Ionic-Level Populations Experimental Data Interaction of Magnetic Oscillations and Waves with Charge Carriers Effect of Charge Carriers in Semiconductors Damping of Magnetic Oscillations Caused by Conductivity Influence of Interionic Electron Transitions Interaction of Spin Waves with Charge Carriers Ferromagnetic Resonance and Spin Waves in Metals Thin-Film Model Theory without Allowance for Exchange Interaction Influence of Exchange Interaction Antiresonance Processes of Magnetic Relaxation Appendices Units and Constants Demagnetization Factors Dirac Delta Function and Kronecker Delta Symbol Bibliography Subject Index to the Bibliography Index

963 Citations

Open accessJournal Article
Tony Low1, Phaedon Avouris1Institutions (1)
31 Jan 2014-ACS Nano
Abstract: In recent years, we have seen a rapid progress in the field of graphene plasmonics, motivated by graphene’s unique electrical and optical properties, tunability, long-lived collective excitation and its extreme light confinement. Here, we review the basic properties of graphene plasmons: their energy dispersion, localization and propagation, plasmon–phonon hybridization, lifetimes and damping pathways. The application space of graphene plasmonics lies in the technologically significant, but relatively unexploited terahertz to mid-infrared regime. We discuss emerging and potential applications, such as modulators, notch filters, polarizers, mid-infrared photodetectors, and mid-infrared vibrational spectroscopy, among many others.

Topics: Graphene (53%), Terahertz radiation (53%)

951 Citations

Open accessJournal Article
Abstract: Landau level quantization in graphene reflects the Dirac nature of its quasiparticles and has been found to exhibit an unusual integer quantum Hall effect. In particular, the lowest Landau level can be thought of as shared equally by electrons and holes, and this leads to characteristic behaviour of the magneto-optical conductivity as a function of frequency Ω for various values of the chemical potential μ. Particular attention is paid to the optical spectral weight under various absorption peaks and its redistribution as μ is varied. We also provide results for magnetic field B as well as chemical potential sweeps at selected fixed frequencies, which can be particularly useful for possible measurements in graphene. Both diagonal and Hall conductivities are considered.

Topics: Landau quantization (63%), Quantum Hall effect (61%), Optical conductivity (58%) ... show more

831 Citations

Journal Article
Se-Ho Lee1, Yeonwoong Jung1, Ritesh Agarwal1Institutions (1)
Abstract: The search for a universal memory storage device that combines rapid read and write speeds, high storage density and non-volatility is driving the exploration of new materials in nanostructured form1,2,3,4,5,6,7. Phase-change materials, which can be reversibly switched between amorphous and crystalline states, are promising in this respect, but top-down processing of these materials into nanostructures often damages their useful properties4,5. Self-assembled nanowire-based phase-change material memory devices offer an attractive solution owing to their sub-lithographic sizes and unique geometry, coupled with the facile etch-free processes with which they can be fabricated. Here, we explore the effects of nanoscaling on the memory-storage capability of self-assembled Ge2Sb2Te5 nanowires, an important phase-change material. Our measurements of write-current amplitude, switching speed, endurance and data retention time in these devices show that such nanowires are promising building blocks for non-volatile scalable memory and may represent the ultimate size limit in exploring current-induced phase transition in nanoscale systems.

Topics: Universal memory (56%), Nanowire (53%)

387 Citations

Open accessJournal Article
Pierre Berini1Institutions (1)
25 Dec 2006-Optics Express
Abstract: Three figures of merit are proposed as quality measures for surface plasmon waveguides. They are defined as benefit-to-cost ratios where the benefit is confinement and the cost is attenuation. Three different ways of measuring confinement are considered, leading to three figures of merit. One of the figures of merit is connected to the quality factor. The figures of merit were then used to assess and compare the wavelength response of hree popular 1-D surface plasmon waveguides: the single metal-dielectric interface, the metal slab bounded by dielectric and the dielectric slab bounded by metal. Closed form expressions are given for the figures of merit of the single metal-dielectric interface.