共查询到20条相似文献,搜索用时 31 毫秒
1.
Ying He Yi Xu Yanfang Yang Weide Huang 《Applied Physics A: Materials Science & Processing》2014,115(3):895-902
An asymmetric quantum well in graphene can act as a slab waveguide for electron waves in a manner analogous to the electromagnetic waves in dielectrics. Guided modes and the probability current density are analyzed in the graphene electron waveguide induced by asymmetric electrostatic potential. The modes in an asymmetric graphene waveguide include guided modes, “cover modes”, “substrate modes” and “radiation modes”. The conditions for a guided mode are quantified. It is found that the fundamental mode is absent when both the Klein tunneling and classical motion are present. The confinement of electrons for lower order mode is stronger than for higher order mode. We hope that these characteristics in asymmetric graphene waveguide can provide potential applications in graphene-based waveguide devices. 相似文献
2.
M. V. Tinin 《Radiophysics and Quantum Electronics》1978,21(12):1200-1208
The author investigates the diffraction of a spherical wave by a smoothly inhomogeneous layer in which a waveguide zone is situated behind a barrier of finite weight. An expression is derived for layer-guided waves generated outside the layer by energy transfer between the waveguide and the external homogeneous half space. Certain properties of these waves are investigated. It is shown that, since the losses associated with energy leakage from the waveguide across the barrier are more significant than the initial wave amplitude at large distances, the role of principal (optimal) mode passes from one mode to another at a lower level in the potential well (waveguide) with increasing distance. The problem of diffraction excitation of ionospheric waveguides in ultralong-range propagation of short radio waves is considered as an example. The results are discussed and compared with published experimental data.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 21, No. 12, pp. 1728–1737, December, 1978.The author is grateful to V. S. Buldyrev for valuable comments, as well as to V. N. Mirolyubov for several useful consultations. 相似文献
3.
We show that it is possible to produce terahertz wave generation in an open waveguide, which includes a multilayer dielectric plate. The plate consists of two dielectric layers with a corrugated interface. Electrons, drifting in the potential well, interact with the non-uniform electric field which is induced near the dielectric interface by the natural wave of the waveguide. The corrugated period and parameters of the electronic system are chosen in order to ensure the most effective interaction of electrons with a wave. Generation of electromagnetic waves is achieved by converting the electrons? energy into the electromagnetic wave energy. 相似文献
4.
Jin-Song Huang Yan-Ling Li Zhong-Hui Xu You-wen Huang 《International Journal of Theoretical Physics》2016,55(9):3934-3942
We investigate single-photon scattering grating in a one-dimensional waveguide coupled to a cavity embedded with a driven Λ-type three-level atom. The single-photon reflection amplitude and transmission amplitude in the waveguide are obtained via a real-space approach, respectively. By spatially modulating a classical control field to drive the three-level emitter, alternating regions of high reflection and absorption as well as high transmission and absorption of the single photon are generated in both directions of the waveguide, which acts as a kind of scattering grating. The proposed scheme may have the potential for the design of chip-integrated grating. 相似文献
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推导了同轴波导的空间电荷限制流,其值大于圆波导的空间电荷限制流。因此在阴极电势和束流相等的情况下,同轴波导中的束流具有更高的动能,同轴器件有可能获得更高的微波转换效率。理论推导出同轴慢波结构中考虑束流空间电荷影响的色散方程,利用Matlab进行了编程求解。不考虑束流空间电荷影响时,编程计算结果与Superfish模拟结果一致。由考虑束流空间电荷影响的色散方程数值计算结果,可知文献中提出的同轴慢波结构相对论高功率微波产生器工作在准TEM模的π模,频率为7.67 GHz,峰值时间增长率较高,电子束损失的能量与其初始能量之比为34%。这些结果均与文献中的数值模拟结果一致。同时理论分析说明该种器件无论在能量转换效率,还是在产生微波脉冲的上升时间上均具有优势。 相似文献
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Heikkinen J.A. Irzak M.A. Shcherbinin O.N. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1998,26(1):26-35
The radiation spectra of a dielectric-filled waveguide (DWG) and a folded waveguide (FWG) antenna in the ion cyclotron range of frequencies are evaluated for tokamaks with the waveguide codes, which model the coupling of the waveguide modes to the plasma waves with outward radiating boundary conditions. The codes provide a self-consistent calculation of the fields across the waveguide apertures for various antenna phasings taking into account a complete set of waveguide eigenmodes including the reflected modes and, in the case of DWG, an arbitrary orientation of the antenna to the plasma magnetic field. In the studied cases, the spectra are found to be well described by a model which is based on a simplified wave field pattern determined by the antenna aperture geometry. Comparison to the corresponding loop antenna is carried out 相似文献
9.
利用时域有限差分方法研究了亚波长金属波导TE波的传播特性和基于异常透射现象的干涉特性.对各种参量对驻波特性的影响及两列波导间的耦合特性进行了分析.研究发现,TE波在波导中传播时存在截止宽度,如果波导宽度小于截止宽度,TE波在波导中不能传播;如果波导宽度大于截止宽度,TE波的传播距离将随波导宽度变大而突然增加.当波导宽度达到或大于半波长时,TE波可以在波导中正常传播.金属波导的截止宽度与金属的吸收系数成正比.此外,由于光在亚波长金属波导透射时的异常透射现象,在亚波长金属波导中产生了TE波的干涉现象,能形成驻波. 相似文献
10.
根据满足边界条件的一系列电磁场方程,采用场匹配法,详细推导了外开槽同轴波导的特征方程。在外开槽同轴波导光滑内同轴半径等于零的情形下,即变成外开槽圆波导,得到其特征方程。数值模拟了外开槽同轴波导及外开槽圆波导中TE01模式的传播特性,得到了不同尺寸外开槽同轴波导开槽间隙半张角和槽深与特征根的变化关系。结果表明:开槽越深,间隙半张角越小,特征根值越小。 相似文献
11.
Yusheng BianZheng Zheng Xin ZhaoYalin Su Lei LiuJiansheng Liu Jinsong ZhuTao Zhou 《Optics Communications》2012,285(24):5118-5121
A novel dielectric slot waveguide supporting strongly confined field in a T-shaped low-index slot region for both TE and TM polarizations is proposed and analyzed. Numerical simulations have demonstrated that quite different birefringent modal properties are achievable with tight optical confinement in the slot by tuning key geometrical parameters of the waveguide. Based on such a slot structure, the characteristics of directional couplers are investigated and the conditions for polarization independent coupling are also given. The presented T-shaped slot waveguide might be employed in integrated photonic systems as important building blocks enabling a number of potential applications. 相似文献
12.
Richard S Ellis 《Contemporary Physics》2013,54(2):159-162
Holographic quantum chromodynamics (QCD) is an extra-dimensional approach to modelling hadrons, the bound states of the strong interactions. In holographic models, the extra spatial dimension creates a waveguide for fields, and the discrete towers of modes propagating in that waveguide are interpreted as hadronic resonances. These models are motivated by the AdS/CFT correspondence, which is a duality that relates theories in different numbers of spatial dimensions. Holographic models have the potential to provide a better understanding of strongly interacting systems of quarks and gluons, as well as unconventional superconductors and other nonperturbative systems. 相似文献
13.
Sanjeev Kumar Raghuwanshi 《Indian Journal of Physics》2010,84(7):831-846
In this paper we have studied the asymmetric versus symmetric planar waveguide in terms of their usefulness in optical fiber communication systems. We have explored the thin
waveguide versus thick waveguide first. Later on usefulness of asymmetric versus symmetric waveguide is carried out to target for WDM optical network application. All kinds of optical network components
are fabricated on Si substrate with the point of view of their application. Here asymmetric planar structure may be more useful
compared to symmetric waveguide in terms of their non-uniform power confinement properties. However, the symmetric waveguide
structure may be more useful for their high power confinement properties. It is well known that the thin symmetric waveguide
supports at least one mode. However the thick waveguide may support many even as well as odd modes. We study the power confinement
properties for symmetric as well as asymmetric waveguide structure. We conclude that higher order modes show the nonlinear
power variations. Mode field profile for various cases is discussed as well. Comparative study between asymmetric versus symmetric waveguide has a lot of significance in optical network area. It has been shown through analysis that in asymmetric
waveguide, the power flows more through film region in the case of fundamental mode. Power confinement properties for asymmetric
waveguide versus symmetric waveguide have been studied. 相似文献
14.
A. K. Sukhorukova A. P. Sukhorukov 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(12):1648-1651
A wave theory was developed and a numerical simulation performed of the diffractive flow of a signal wave around a negative
inhomogeneity induced by a cylindrical pump beam in nonlinear medium while keeping both waves in the potential well. It was
shown that a broad pump beam reflects a narrow signal beam. A nonlinear waveguide (a dark soliton) is described as well. These
phenomena can be observed in Bose-Einstein condensate (BEC) and in a gradient waveguide. 相似文献
15.
A technique to solve generalized dispersion equation of multilayer planar waveguide has been demonstrated to obtain all the expected guided modes. The solution is based on the derivative free method for computing the zeros of an analytical function in complex plane. The derivative free method extracts the roots which are very close to actual zeros of the function. Roots are further refined using the robust iteration method to achieve the desired accuracy. Application of the proposed method has been verified by solving the modes of a variety of structures including lossless structure, leaky structure, quantum well waveguide, active waveguide, ARROW waveguide and metal clad waveguide. The method is efficient and computes all modes of planar waveguide with high accuracy. 相似文献
16.
The modified ray-optics method is used to analyze the coupling efficiency from a Gaussian beam to a rectangular multimode embedded strip waveguide. It is convenient for analyzing the case of a simple waveguide structure because of reduced computation time. The conditions for determining which optical rays can be coupled into the waveguide to become the waveguiding modes, as well as the effective receiving area of the waveguide, are derived in this work. The data obtained by this method are compared with those calculated by the well-known overlap integral theorem and Marcatili's models for investigating the validity of the modified ray-optics method. 相似文献
17.
《Superlattices and Microstructures》1994,15(2):69
A theoretical study on the tunneling spectroscopy of an electron waveguide recently observed by Eugster and del Alamo is presented. A narrow electron waveguide coupled with another much wider one by a thin barrier between them is taken as a theoretical model for the leaky electron waveguide implemented by Eugster et al., and the transport properties of electrons are studied comprehensively through the wavefunction of the system. The results demonstrate that the conductance for the current tunneling out the barrier oscillates strongly with the width of the narrow electron waveguide, in line with its conductance steps. The theory is in good agreement with the experiments and confirm that the oscillations of the tunneling current can be considered as a spectroscopy of the 1D DOS (one dimensional electron density of states) in the electron waveguide as proposed by Eugster et al. In order to study the effects of scatterers on the transport properties of the leaky electron waveguide, a δ-function is used to simulate the scattering potential The results show that the presence of even a single scatterer located in the waveguide will lead to obvious distortion of the shape of conductance steps, and will greatly influence the oscillations of the tunneling current observed in clean waveguides. However the effects of scatterers located outside the tunneling barrier on either the conductance steps or the oscillations of the tunneling current are negligible. 相似文献
18.
Magnetotransport in a dual waveguide coupled by a finite barrier: Energy filter and directional coupler
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We propose in this paper that a dual waveguide coupled by a finite
barrier be able to serve as an energy filter under a perpendicular
magnetic field. In the waveguide direction, the conductance exhibits
a periodic square-wave pattern in which the miniband is controlled
by the magnetic and potential modulation. The electrons with
energies in the miniband can completely transfer along one waveguide
while the other electrons undergo filtration. Compared with the
coupled waveguide without magnetic modulation, the structure under
magnetic field is found to be a good directional coupler. By
adjusting the potential barrier and magnetic field, the electrons
input from one port of waveguide can transfer to any other ports. 相似文献
19.
Denis Borisov 《Mathematical Physics, Analysis and Geometry》2007,10(2):155-196
We consider a quantum waveguide modelled by an infinite straight tube with arbitrary cross-section in n-dimensional space. The operator we study is the Dirichlet Laplacian perturbed by two distant perturbations. The perturbations are described by arbitrary abstract operators “localized” in a certain sense. We study the asymptotic behaviour of the discrete spectrum of such system as the distance between the “supports” of localized perturbations tends to infinity. The main results are a convergence theorem and the asymptotics expansions for the eigenvalues. The asymptotic behaviour of the associated eigenfunctions is described as well. We provide a list of the operators, which can be chosen as distant perturbations. In particular, the distant perturbations may be a potential, a second order differential operator, a magnetic Schrödinger operator, an arbitrary geometric deformation of the straight waveguide, a delta interaction, and an integral operator. 相似文献
20.
A compact and sensitive electro-optical sensor based on slotted photonic crystal waveguide (S-PhCW) is demonstrated. The electro-optical sensor can be realized in photonic crystal (PhC) slabs of silicon in Silicon-on-Insulator (SOI). Nonlinear optical polymer is used as infiltration. By applying three-dimensional finite difference time domain (3D-FDTD), the sensitivity and quality factor of electro-optical sensor with different slotted waveguide width are calculated. In addition, sensitivity and the optical properties such as transmission spectrum and field distributions are compared between electro-optical sensor based on line defect photonic crystal waveguide (W1-PhCW) and that based on slotted photonic crystal waveguide (S-PhCW). Simulation results demonstrate that, compared with electro-optical sensor based on line defect photonic crystal waveguide, the sensitivity and quality factor is improved by 30 times and 6.6 times respectively in sensor based on slotted photonic crystal waveguide. Besides, the proposed PhC sensor devices have the advantage of a compact structure with the potential for monolithic integration with optical-to-electrical on-chip conversion and detection. 相似文献