对称单负介质包层平面波导的模式特征

系统研究了负μ材料(MNG)作为包层的对称三层平板波导的传输特性. 研究发现,这种波导既支持快波的传播,又支持TE₀,TE₁模式的慢波传输. 其模式特性不同于左手介质波导和传统介质波导,导模存在的模折射率范围要比它们的大. MNG波导的TE₀快波模缺失,且TE_m模(m>1)的传播常数大于TM_m模的传播常数. TE_m模具有双模特征,且与波导的结构参数密切相关,导致波导中的净能流出现负值. 关键词： 单负介质 平板波导 快波与慢波 传播常数     

微波频段表面等离子激元波导滤波器的实验研究

基于理论分析, 实验研究了二维磁单负材料/双正材料/磁单负材料表面等离子波导的滤波效应. 研究表明, 该波导结构具有低通滤波性质, 引入分支缺陷之后, 由于谐振效应该波导具有带阻滤波效应. 分支缺陷相当于亚波长谐振腔, 谐振腔的长度决定带阻滤波器的中心频率, 而中心频率几乎不受缺陷位置的影响; 滤波器透射率下降的幅度由耦合距离决定. 通过引入谐振腔及改变谐振腔的长度、数量以及耦合间距等参数, 可以实现可调节的表面等离子波导滤波器. 实验结果与理论分析符合得很好, 该性质将在可调的单通道或多通道带阻滤波器件中具有潜在的应用价值. 关键词： 表面等离子激元 特异材料波导 谐振腔 滤波器     

同轴交错圆盘加载波导慢波结构高频特性的研究

采用多导体传输线分析方法, 对同轴交错圆盘加载波导慢波结构进行了理论分析, 得到了这种慢波结构的色散方程; 利用该色散方程, 得到的色散特性与HFSS仿真软件模拟结果符合良好. 分析了结构参数的变化对同轴交错圆盘加载波导慢波结构的色散特性影响. 结果表明: 增加内径和减小慢波结构的单位周期长度可以拓展慢波结构的带宽. 对同轴圆盘加载波导和同轴交错圆盘加载波导两种慢波结构的色散特性进行了比较, 结果表明: 采用圆盘交错加载方式可以减弱色散, 拓展带宽. 研究结果对同轴交错圆盘加载波导在毫米波行波管中的应用具有指导意义. 关键词： 行波管 同轴交错圆盘加载波导 慢波结构 色散特性     

曲折圆形槽波导慢波系统的高频特性

 对曲折圆形槽波导新型慢波系统的高频特性进行了研究，通过理论分析和数值计算，得到了它的色散曲线和耦合阻抗表达式，并分析了结构参数变化对色散特性和耦合阻抗的影响。研究表明：当周期变小时色散减弱，耦合阻抗增加；而增大直波导长度时色散变弱，但同时耦合阻抗也会下降。因此较小的周期有利于改善曲折圆形槽波导慢波电路的高频特性。鉴于这种电路的耦合阻抗较低，可以适当地减小直波导长度来提高耦合阻抗。曲折槽波导结合了曲折波导散热能力强、色散特性好、容易加工和槽波导单模工作、低损耗、大尺寸等优点，在毫米波及亚毫米波段的行波管中具有较好的发展前景。     

负折射率材料对Casimir效应的影响

研究了负折射率材料介质板间的Casimir效应.对于负折射率材料中由Drude-Lorentz型色散关系描述的介电常数和磁导率，色散曲线中负值频带的曲线结构由各色散吸收参数所决定，色散曲线负值频带宽度和负区域的深度等性质的变化影响了介质材料板的反射特性，进而对两材料板间的Casimir效应强弱起着重要的作用.     

椭圆截面等离子体柱离子回旋频率附近的本征振荡

本文用椭圆柱座标系导出了波导管中和自由边界情况下波的色散关系,计算了椭圆截面波导管中快磁流体波和慢波的本征模。通过计算得出,在时,快波可以在等离子体的高密度区域传播,而慢波只能在低密度区域传播。     

非互易旋电材料硅基矩形波导的色散特性研究

研究设计了基于光通信C波段旋电材料的矩形波导,利用有效折射率法对波导有效折射率及横向电场分布进行求解,得到矩形波导中E_(mn)~x导模的色散方程.研究了在外磁场作用下表面磁等离子体激元的非互易传播特性.还研究了结构参数和材料折射率对非互易色散关系、时延特性的影响.结果表明:其色散曲线随波导宽度的递增逐渐趋向平面波导;群速度v_g与波导宽度、传播常数、工作波长相关;矩形波导芯区宽度在140—233.5 nm范围内的波导工艺容差较大; v_g与矩形波导y方向包层材料折射率成正相关,当材料为金属银时慢光效应最明显,传输速度最小可以达到2.8×10~(–3)c.     

负介电常数材料和负磁导率材料的双层结构中电磁波模式分析

研究了双层单负材料结构中电磁波的模式,主要分析了不同模式的产生条件,讨论了这些模式与材料参数之间的关系.当材料参数满足平均介电常数和磁导率为零时出现隧穿模式.当满足波导模产生条件时,波导模式的电磁波在材料两边的半无限真空中以消逝波存在,在双层单负材料的界面处也可以出现较强的局域场. 关键词： 单负材料 传播模式 隧穿模式 波导模式     

光子晶体波导慢光特性研究

基于二维三角晶格空气孔光子晶体,通过在光子晶体单线缺陷波导两侧引入不同的耦合腔,设计了慢光特性较好的波导结构.利用平面波展开法计算波导的色散曲线,并分析慢光模式的群速度和群速度色散特性.耦合腔采用单缺陷腔时,适当调节波导宽度可以获得在零色散点群速度为0.0128c的慢光模式,对应在1.55 μm波长处的带宽为409 G...     

基于Drude-FDTD算法的单负介质组合填充波导传播特性研究

提出了电单负介质和磁单负介质组合填充矩形波导结构,通过理论分析和修正的3D-Drude-FDTD算法进行数值仿真,分析了电磁波在其中的传播特性.仿真结果表明,新结构波导中存在异于传统介质填充波导的亚波长导模,且传播常数基本不随频率的变化而变化,可以用于宽带微波器件和天线的设计. 关键词： 单负介质 传播常数 截止频率 时域有限差分法     

Specific features of the propagation of electromagnetic waves in a waveguiding structure with superconducting film and metamaterial

The propagation of electromagnetic waves in a rectangular waveguide containing layers of common dielectric and metamaterial with a negative refractive index separated by a thin film of a superconductor of the second type in the mixed state is considered. The possibility of amplifiying waves at frequencies lower than the cutoff energy due to the energy of an Abrikosov vortex lattice moving in the superconductor is demonstrated.     

Surface waves guided by magnetic metamaterials

We consider electromagnetic waves guided by slabs of anisotropic resonant magnetic metamaterials in free space and in metal waveguides. It is shown that wave propagation is possible in a waveguide below cutoff with an insert of such a metamaterial. The dependence of the dispersion properties of waves on the geometric sizes of the insert and the waveguide are studied. The obtained results can be used for miniaturization of electrodynamic systems. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 7, pp. 618–625, July 2006.     

Trapping of electromagnetic wave in single-negative metamaterial waveguides

We study the trapping properties of transverse magnetic (TM) waves in single-negative metamaterial waveguides including epsilon-negative (ENG) metamaterial and mu-negative (MNG) metamaterial. The relationship between effective refractive index and reduced core width is analyzed when the permittivities of ENG and MNG metamaterials are different, and the inflection on this curve can be regarded as the trapping point. Simulation results show that the properties in an ENG–MNG–ENG metamaterial waveguide are contrary to that in a MNG–ENG–MNG metamaterial waveguide. The sensitivity of trapping point to the change of permittivity makes the single-negative metamaterial waveguides to be an effective method to detect the permittivity variation and can be used as a new kind of waveguide sensor.     

Surface modes in an asymmetrical waveguide with dispersive single-negative metamaterial

We study the group-velocity of surface modes which indicates the direction of power propagation by analysis of the dispersion curves in an asymmetrical waveguide with dispersive epsilon-negative (ENG) metamaterial. The expressions of transverse magnetic (TM) surface mode and its magnetic field distribution are derived based on which simulation results are given to discuss the influence of electromagnetic parameters of the constructive material and the configuration of the waveguide on the propagation direction of surface modes.     

Anomalous dispersion and group velocity properties in subwavelength uniaxial metamaterial waveguide with metal cladding

We investigate propagation behavior of electromagnetic waves in a slab uniaxial metamaterial waveguide with metal cladding and discuss the dispersion relation, group velocity and energy flux distribution of transverse electric guided modes in two kinds of uniaxial metamaterial waveguides with different orientations of optical axis in detail. The numerical results show that there exist anomalous dispersion properties such as backward modes existing in low-frequency range, and the group velocity can be negative or approach zero. If the orientation of optical axis is selected properly, each guided mode has two dispersion curves—one is normal dispersion and another belongs to anomalous dispersion and shows a transition from a backward mode to a forward one with the angular frequency increasing. In addition, the condition of the existence of cutoff frequency is clarified. These properties may have potential applications in optical information storage, optical communication, integrated optics and nanophotonic devices.     

Enhancement of single mode operation in coaxial optical waveguide using DB boundary conditions

In this study, a competent numerical strategy to compute the dispersion of optical waveguides is presented and propagation of electromagnetic waves in a coaxial optical waveguide with DB boundary conditions is instigated. For this intend, cylindrical coordinates are here being used to derive the DB boundary conditions and to obtain field components for the modes. The propagation constant for the waveguide to be studied is determined by solving the Bessel and the modified Bessel functions. The cutoff frequencies for various lower order modes have been calculated and their dispersion characteristics are plotted correspondingly. The behavior of the coaxial optical waveguide under DB boundary conditions is shown to be significantly different from that of coaxial optical waveguide and conventional optical waveguide under traditional or tangential boundary conditions. Finally, the effect of waveguide dimensions on the mode cutoff frequencies and fabrication issues are also addressed.     

Phase constant peculiarities of cylindrical zero-index anisotropic metamaterial waveguide

Here, we present the phase constant dependencies of propagating eigenmodes of an open cylindrical anisotropic metamaterial waveguide when the metamaterial permittivity and permeability tensor components may accept values close or equal to zero. Dispersion characteristics of rod and hollow-core waveguides with the radii 0.5, 2.5, and 5 mm at the left-handed polarization of the microwave are shown here. There are unusual shapes of eigenmode dispersion characteristics and anomalous sectors of the characteristics at certain frequencies. The first eigenmode of the rod waveguide with the lowest cutoff frequency is a particularly important mode because it is a single one in the frequency range 1.0?C1.9 GHz, and some small variations on the frequency produce large changes in the phase constant. We can observe packages of dispersion characteristic branches when their cutoff frequencies closed to the metamaterial electric and magnetic plasma frequencies between 1.9 and 3.5 GHz. There are only three modes in the hollow core anisotropic metamaterial waveguide at the frequency range 1.4?C2.8 GHz.     

Transmission characteristics of wave modes in a rectangular waveguide filled with anisotropic metamaterial

In this paper, transmission characteristics of wave modes in a rectangular waveguide filled with lossless anisotropic metamaterial are theoretically investigated. The wave equation and dispersion relations for TE and TM modes in the waveguide are obtained and analyzed. It is shown that the negative constitutive parameters of the filling anisotropic metamaterial can be used to control the wave magnitude and the phase velocity direction in the waveguide over the entire frequency domain, both below and above the cutoff frequency. Particularly, not only backward waves, but also forward waves can propagate below the cutoff frequency in the waveguide. Furthermore, a typical example is calculated to demonstrate transmission characteristics of waves inside the waveguide. Numerical results are obtained in the paper and compared with theoretical predictions: a good agreement is found.     

Metamaterial layer in rectangular waveguide

The changes in the dispersion characteristics of modes of isotropic metamaterial layer in a rectangular waveguide have been analyzed. It is shown that metal walls significantly affect the mode dispersion due to the redistribution of energy fluxes and broaden the waveguiding properties of the layer to the propagation range of fast waves. A variation in the waveguide parameters makes it possible, in particular, to implement an interesting class of eigenmodes with fast forward and slow backward waves.