The surface plasmon polariton dispersion relations in a nonlinear-metal-nonlinear dielectric structure of arbitrary nonlinearity

The analytic surface plasmon polaritons(SPPs) dispersion relation is studied in a system consisting of a thin metallic film bounded by two sides media of nonlinear dielectric of arbitrary nonlinearity is studied by applying a generalised first integral approach.We consider both asymmetric and symmetric structures.Especially,in the symmetric system,two possible modes can exist:the odd mode and the even mode.The dispersion relations of the two modes are obtained.Due to the nonlinear dielectric,the magnitude of the electric field at the interface appears and alters the dispersion relations.The changes in SPPs dispersion relations depending on film thicknesses and nonlinearity are studied.     

Impurity-induced local modes in one-dimensional dusty plasma chains

The effects of impurity on eigenmodes in one-dimensional dusty plasma lattices are studied.It is found that local modes can be excited besides lattice waves,due to the existence of an impurity particle.The dispersion relations of the modes are derived accordingly.Properties of the lattice and local modes are also analyzed and discussed,particularly for their symmetric features and conditions of the mode excitation.     

The relationship between acoustic radiation modes and structural modes and its applications

Both acoustic radiation modes and structural modes play an important role in the field of structure-borne sound, however, little work has been done for inherent relations between these two kinds of modes. This paper is focused on the relationship between the radiation modes and structural modes and its physical mechanisms. First, a governing equation for relating the radiation mode and structural mode is given based on the characteristics of the modes. Then, using the symmetric or anti-symmetric properties of two kinds of modes, the corresponding relations are presented. And then, numerical examples are given to verify the theoretical investigations, and it has been shown that, for a simply supported rectangular panel vibrating at low frequencies, the first radiation mode is dominant corresponding to (odd, odd) structural modes; the following radiation modes are respectively dominant corresponding to (even, odd), (odd, even), and (even, even) structural modes. Finally, such relations are applied to active acoustic structural control and provide a direct help for the design of active control strategy and arrangement of the secondary forces.     

Electron-Phonon Interaction in an Annular Quantum Dot

The confined longitudinal-optical （LO） phonon and surface-optical （SO） phonon modes of a free-standing annular cylindrical quantum dot are derived within the framework of dielectric continuum approximation. It is found that there exist two types of SO phonon modes： top SO （TSO） mode and side SO（SSO） mode in a cylindrical quantum annulus. Numerical calculation on CdS annulus system has been performed. Results reveal that the two different solutions of SSO mode distribute mainly at the inner or outer surfaces of the annulus. The dispersion relations and the coupling intensions of phonons in a quantum annulus are compared with those in a cylindrical quantum dot. It is found that the dispersion relations of the two different structures are similar, but the coupling intension of the phonon-electron interaction in quantum annulus is larger than that in quantum dot. The Hamiltonians describing the free phonon modes and their interactions with electrons in the system are also derived.     

Decomposition of the Two Lowest Lamb modes in a Bonded Plate

Based on the expression of the dispersion equation of Lame waves in an adhesive two-layered plate pressented in our proevious paper [Chin,Phys,Lett,18(2001)1483],the two lowest Lamb modes,the symmetric mode S0 and the antisymmetric mode A0 are successfully decomposed in the low-frequency regime,Relations between the rigidity of the bond and the velocity of the two Lamb modes are found,which lay a foundation for the estimation of the bond rigidity of the adhesive plate.The influence of the variations of the bond rigidity in terms of the stiffness constants KN and KT of the spring model on the velocity of the two Lamb modes in discussed and numerically evaluated.numerical results indicate that the deterioration of the bond rigidity causes the phase velocity decrease for Lamb modes of the two lowest order,thus having a possibility for the evaluation of the bonding state of the adhesive plate by using ultrasonic wave velocity measurement.     

Effects of Extension and Overlap of Wavefunctions on Plasmon Modes in Symmetric Double—Quantum—Well Structures

We investigate the effects of extension and overlap of wavefunctions on the dispersion relations of plasmon modes in symmetric double-quantum-well structures.We compare the approximate results in two-dimensional layer-gas (2DLG) model with the exact ones where the extension and overlap of the wavefunctions are included.Our numerical results show that the 2DLG model is a good approximation only in the wide barrier case in the long wavelength limit.When the barrier is thin,the extension and overlap of the wavefunctions cannot be neglected.We also show that the long wavelength gap of the inter-subband mode is proportional to the energy difference between the ground and the first excited energy levels.     

Parallel propagating modes and anomalous spatial damping in the ultra-relativistic electron plasma with arbitrary degeneracy

The dispersion relations of parallel propagating modes(Langmuir mode, right and left handed circular polarized waves) in the weak magnetic field limit |ω-k·v| ? are considered for ultra-relativistic arbitrary degenerate electron plasma. The results are presented in terms of moments of Fermi-Dirac distribution. The increase in the electron equilibrium number density from negative large(weakly degenerate) to positive large(highly degenerate) values of μ/T_e is observed(where μ is the electron chemical potential and T_e is the electron thermal energy). As a result, shifting of the cutoff points in all the real dispersion branches towards the higher values and increasing in the band gap between unmagnetized longitudinal and transverse modes in k-space are examined. Also, the suppression of the weak magnetic field effects in weakly magnetized right handed and left handed circular polarized waves and a decrease in the longitudinal and transverse screening effects are observed in the graphical patterns due to an increase in the equilibrium number density.     

Defect Modes in Multiple-Constituent One-Dimensional Photonic Crystals Examined by an Analytic Bloch-Mode Approach

Defect modes in one-dimensional photonic crystals (PCs) can be readily detected from the solution of the trans-mission spectra via the standard transfer-matrix method. We adopt an analytic Bloch-mode approach to examine this problem in terms of eigenmode solutions and investigate the dispersion behaviour of localized defect modes supported by a defect layer sandwiched within two symmetric semi-infinite PCs that are made from multiple constituents. The results show that the number of defect modes grows when the dielectric constant and width of the defect layer increase.     

Coupled edge plasmon modes of metal/dielectric multi-wedges

We present a metallic/dielectric multi-wedge model to investigate the coupled edge plasmon modes （CEPMs）, where all wedges have a common edge and the wave propagates along the edge direction. A general theoretical method valid to many practical structures is presented. The analytical dispersion relations of CEPMs in these structures are obtained and the CEPM properties are discussed with numerical results and the dispersion relations. For all structures mentioned in this paper, we find that the structures containing an even number of metallic wedges have four CEPMs and those with an odd-number of metallic wedges have two CEPMs. Further, the periodic structures containing any odd number of periods and any even number of periods possess their common CEPMs, respectively.     

Polar Oscillation of Interface and Surface Optical Phonons in Free-Standing Cylindrical Quantum-Well Wires

Under dielectric continuum approximation, interface optical (IO) and surface optical (SO) phonon modes as well as the corresponding Fro^ehlich electron-phonon interaction Hamiltonian in a free-standing cylindrical quantum-well wire (QWW) are derived and studied. Numerical calculations on GaAs/AlzGa1-x As cylindrical QWW are performed. Results reveal that there are two branches of IO phonon modes and one branch of SO phonon mode, and the dispersion frequencies of IO or SO phonon modes sensitively depend on the Al mole fraction x in AlzGa1-x As material and the wavevector in z direction, kz. With the increasing of kz and quantum number m, the frequency of each IO mode approaches one of the two frequency values of the single GaAs/AlxGa1-x As heterostructure, and the electrostatic potential distribution of the phonon mode tends to be more and more localized at a certain interface or surface, meanwhile, the coupling between the electron-IO and -SO phonons becomes weaker.     

转移矩阵法在负折射率介质材料平板波导中的应用研究

利用严格电磁理论，推导出了适用于负折射率介质材料光波导的转移矩阵，分析讨论了转移矩阵的性质和应用.利用转移矩阵方法，推导出导波层为负折射率介质材料、覆盖层和衬底为右手材料的三层对称介质光波导的本征色散方程.用图解法研究了负折射率介质波导中TE波的异常色散特性.在负折射材料介质波导中没有零阶模，最低阶为1阶模，并且有截止频率,只有波导参量满足一定条件的时候才会存在，导模的横向波数可以为实数和纯虚数，而正折射率介质波导导模的横向波数只能为实数.     

Wave propagation in parallel-plate waveguides filled with nonlinear left-handed material

A theoretical investigation of field components for transverse electric mode in the parallel-plate waveguides has been studied. In this analysis two different types of waveguide structures have been discussed, i.e., (a) normal good/perfect conducting parallel-plate waveguide filled with nonlinear left-handed material and (b) high-temperature-superconducting parallel-plate waveguide filled with nonlinear left-handed material. The dispersion relations of transverse electric mode have also been discussed for these two types of waveguide structures.     

Quantum Theory of Surface Polaritons on a Rough Surface

In this paper, we present the quantum field theory of the surface phonon-polaritolis on a rough polar crystal surface. The dispersion relations of the surface phonon-polaritons and the dispersion relations of polariton leaking modes owing to the interaction between bulk TO mode with the surface effect and photons are derived. We also study the k-dependence of the electric field strength in each polariton branch. The numerical calculations for the dispersion relations and the k-dependence of the electric field strength are carried out for a stepped Gap surface. The results show that the surface roughness depressed the frequency of the surface phonon-polariton below its values in the absence of the surface roughness. For the frequencies of the polariton leaking modes, the photon-like one is enhanced by the surface roughness and the phonon-like one b depressed. Our evaluations also illustrate that the surface roughness introduces a strong dependence on the k-dependence of the electric field strength in each polariton branch.     

非对称型Kerr类介质膜漏波导中的非线性导波

本文研究了特定边界条件下非对称型Kerr类介质膜漏波导中TE₀光波的传播特性。计算结果表明,介质膜厚存在一临界值。临界值之上没有导波存在,临界值之下能同时存在强场TE₀模和弱场TE₀模,它们具有不同的传播波数。这两个模的膜内传播功率、场强峰值位置随膜厚和光场频率的变化各不相同,色散关系也有极大差别。在对称极限之下,弱场TE₀模的色散为零。 关键词：     

Optical waveguide with nonlinear walls

The modes of planar waveguides with thin walls, consisting of nonlinear materials, are studied. The dispersion relations are derived and analyzed by analytical and numerical techniques. The effect of modal type conversion is examined. It is shown that the leaky mode can be converted to the virtual one when the field amplitude is varied.     

Optical modes in a plasmonic waveguide with electrically anisotropic metamaterial

We study the optical modes in a plasmonic waveguide with electrically anisotropic metamaterial and dielectric, including symmetric (anti-symmetric) photonic mode and symmetric (anti-symmetric) plasmonic mode. The dispersion curves for these modes are derived, and a graphical method is used to calculate the solution of symmetric photonic mode and anti-symmetric plasmonic mode. By simulation results the conditions of the existence for these modes are deduced in each case.     

基于类表面等离子体激元的矩形金属光栅色散特性的研究

等离子体激元(surface plasmon polaritons, SPP)因其独特的光学和物理特性, 使其具有诸如透射增强和局域共振等一系列新颖现象, 已成为当前国内外学者研究的热点. 本文对基于类表面等离子体激元(Spoof Surface Plasmons, SSP)的矩形金属光栅色散特性和模式分布进行了研究. 利用本征函数法并结合场匹配条件, 获得了矩形栅表面SSP的场表达式、色散关系和模式分布, 并通过电磁仿真进行了验证. 在此基础上分析了矩形栅各参数对SSP色散及模式分布的影响, 研究结果表明: 由本征函数法获得的SSP色散特性与仿真结果基本符合; 增大金属栅高度或减小排列周期能减小SSP的相速度; 而增大金属栅周期占空比能在一定程度上拓展SSP与电子束互作用的带宽; 改变金属盖板高度对慢波SSP色散模式基本没有影响; 减小金属栅侧面宽度能增大模式之间的间隔, 从而能有效避免模式竞争的发生. 本文对基于SSP的矩形金属光栅色散特性的研究将为进一步研究SSP与电子束的相互作用, 形成高效、宽带的新型太赫兹源奠定良好的理论基础.     

Microscopic modes in a Fermi superfluid. II. Dispersion relations

This is the second of two papers in which microscopic expressions for the amplitudes and dispersion relations for hydrodynamic modes in an isotropic Fermi superfluid are derived. In this paper we obtain approximate solutions to the linearized kinetic equations for the bogolon spin density and total density for the case of long-wavelength disturbances after long times when a fluctuating superfluid velocity is present. In so doing, we obtain microscopic expressions for the amplitude and dispersion relations for the spin diffusion mode, the two shear modes, and the four longitudinal modes (two first-sound modes and two second-sound modes).