填充右左手材料矩形屏蔽微带线色散特性的比较研究

运用矢量有限元法对填充右左手材料的矩形屏蔽微带线的色散特性进行比较研究,包括矩形单信号对称屏蔽微带线,矩形单信号不对称屏蔽微带线,矩形双信号对称屏蔽微带线,矩形双信号位置不对称屏蔽微带线,矩形双信号宽度不对称屏蔽微带线以及矩形双信号厚度不对称屏蔽微带线六种情况.讨论这些屏蔽微带线的主模色散特性随填充材料的变化,色散特性的研究有助于矩形屏蔽微带线和左手材料在新型微波器件中的应用.     

Analytical analysis of circular-shaped microshield and conductor-backed coplanar waveguide

In this paper, a new type of circular-shaped microshield and conductor-backed coplanar waveguide is proposed. Analytic closed-form expressions for characteristic impedance and effective dielectric constant for the new line are obtained using conformal mapping method under the assumption of pure-TEM propagation and zero dispersion. The new waveguide proposed by this paper can reduce radiation to much less than the conventional coplanar waveguide and microstrip, and can reduce the current concentration at both the edges of the strip conductor.     

Multiple scatter of vector electromagnetic waves from rough metal surfaces with infinite slopes using the Kirchhoff approximation

This paper presents calculations of a new formulation of the three‐dimensional Kirchhoff approximation which allows calculation of the scattering of vector waves from two-dimensional (2D) metal and dielectric rough surfaces containing infinite slopes. Results are presented for scattering from metal surfaces with rectangular surface structures. This type of surface has applications, for example, in remote sensing and in testing or imaging of printed circuits. Some calculations for rectangular-shaped grooves in a plane are presented for the 2D surface method and are compared to previously published results using a different method of calculation. Good agreement is found between the results for the different calculation methods.     

Rigorous analysis of novel dielectric resonator filters with printed tuning septum

This paper describes the analysis of dielectric resonator filters with printed tuning septum in waveguide sections operating below cutoff. In this design approach a thick dielectric slab of high permittivity is placed longitudinally in the waveguide. A bilateral ladder-shaped metallization determines the resonator and coupling sections (modified finline filter). In contrast to conventional dielectric resonator filters, this approach provides better passband separation and increased stopband attenuation. Furthermore, due to the bilateral tuning septum, the resonator and coupling sections can be manufactured accurately with photolithographic techniques rather than by expensive machining.     

Dispersion Characteristics of Dielectric Loaded Multiple V-Ridge Waveguide

A new kind of V-ridge waveguide is presented in this paper. The transmission problem is solved by edge element for the first time. The field patterns of the waveguide with single, double and triple V-ridge for different values of dielectric constant have been presented. Variations of the cutoff wavelength, single-mode bandwidth with the ridge dimensions for different values of dielectric constant are investigated in detail. The results will be of practical significance in designing ridge waveguide components in microwave and millimeter wave engineering.     

The conduction regime in a nematic liquid crystal with negative dielectric anisotropy at frequencies above the dielectric relaxation frequency

Due to the relaxation of the longitudinal dielectric constant, the dielectric anisotropy in a nematic liquid crystal may change sign and become negative. This gives rise to a conduction regime with negative dielectric anisotropy at high frequencies. The width and cutoff frequency of this conduction regime are calculated.     

金属覆盖介质波导在截止点附近的光学特性

本文提出一种适合于截止点附近计算含金属覆盖层介质波层的近似解析方法，详细；地讨论在截止点附近的光波导的模式传播特性 和光电调制特性，并结合有效折射率方法讨论了止型脊形波导调制器的截止条件。     

手征材料构成的简立方光子晶体光子带结构计算——平面波法

发展了适于计算由手征材料组成的光子晶体的光子带结构的平面波法。在此基础上，研究了由手征材料组成的简立方光子晶体的光子带结构。计算表明：手征材料“球形原子”在电介质中排列所组成的科立方光子晶体和电介质“球形原子”在手征材料中排列所组成的简立方光子晶体，不仅都存在光子带隙，而且存在截止频率，在该频率以下的区域无传播模存在，本语文认了这种光子晶体的潜在应用。     

外磁场与温度对低温超导光子晶体低频禁带特性的影响

文中用传输矩阵法(TMM)分析了TM波垂直入时,超导光子晶体的低频禁带特性,并讨论了外磁场与温度对禁带的影响.分析结果表明:超导光子晶体存在频率从0开始的低频禁带;当没有外磁场作用时,由于超导中正常态电子的影响,低频禁带的截止频率与温度无关;有外磁场作用时,温度才对截止频率具有可调性.外加恒定磁场时,低频禁带的截止频率随温度升高而减小;而在正常态电子的作用下,温度对处在超导态超导光子晶体禁带截止频率的调节范围相对忽略正常态电子情况下减小.恒温下,通过调节外磁场来控制带隙时,正常态电子的贡献很小可忽略不计;外磁场强度增大禁带截止频率减小.当超导体完全处于正常态时,低频禁带消失.     

Phase-matching condition between acoustic and optical waves in doped fibers

A new technique, recently proposed [1] for achieving phase-matching in Brillouin scattering in a dielectric fiber doped by three-level Λ-type ions, can lead to a dramatic increase of efficiency of ponderomotive nonlinear interaction between electromagnetic waves and holds promise for applications in quantum optics. In this paper, we investigate possibilities to establish phase-matching condition for acoustic modes in confined geometries that exhibit nonzero cutoff frequencies.     

A Cutoff Waveguide ICRF Coupler for Large Tokamaks

This paper proposes a cutoff waveguide Ion-Cyclotron Range of Frequencies (ICRF) coupler in heatings of fusion plasma for large tokamaks. Structures of tokamaks do not permit enough aperture areas for using cylindrical waveguides in the propagative region. However, if the power source to excite the coupler is located near its aperture, electromagnetic power is expected to pass through the cutoff region as a tunnel effect and radiate into the fusion plasma. We calculate characteristics of the normalized radiation power and the input impedance for this cutoff waveguide coupler, regarding its aperture as a slot. Numerical results show that the cutoff waveguide coupler has a few million watts handling power when the effective dielectric constant of the plasma is between 60 and 100. Experiments for a one-tenth model of actual size are performed using air and water instead of the fusion plasma. Measured input impedance showed a fine agreement with the theory for typical ones. Furthermore, experiments verify that its input impedance can be controlled by the location of a short-circuiting plunger. All these results suggest that the cutoff waveguide coupler is very attractive for ICRF heating.     

Dispersion characteristics of two-dimensional unmagnetized dielectric plasma photonic crystal

This paper studies dispersion characteristics of the transverse magnetic (TM) mode for two-dimensional unmagnetized dielectric plasma photonic crystal by a modified plane wave method. First, the cutoff behaviour is made clear by using the Maxwell--Garnett effective medium theory, and the influences of dielectric filling factor and dielectric constant on effective plasma frequency are analysed. Moreover, the occurence of large gaps in dielectric plasma photonic crystal is demonstrated by comparing the skin depth with the lattice constant, and the influence of plasma frequency on the first three gaps is also studied. Finally, by using the particle-in-cell simulation method, a transmission curve in the \Gamma -X direction is obtained in dielectric plasma photonic crystal, which is in accordance with the dispersion curves calculated by the modified plane wave method, and the large gap between the transmission points of 27~GHz and 47~GHz is explained by comparing the electric field patterns in particle-in-cell simulation.     

Vacuum energy in the presence of dielectric and conducting surfaces

The polarization of the electromagnetic vacuum is examined in the neighborhood of dielectric and conducting surfaces and the energy associated with this polarization is shown to depend on a cutoff related to the microstructure of the boundary. The appearance of the cutoff permits the vacuum energy to be expressed in terms of a surface tension and certain higher shape tensions. For the case of a dielectric boundary the surface tension reproduces the Schmitt-Lucas formula which accounts reasonably for the observed surface tensions of many materials. The curvature tension is also calculated and it seems the effect of this energy may well be accessible to experimental verification. For the case of perfectly conducting surfaces the first four shape tensions are calculated. It is shown that previous calculations of the vacuum energy due to perfectly conducting surfaces are in error and these errors are corrected.     

Transmission properties of Fibonacci quasi-periodic one-dimensional superconducting photonic crystals

The transmission properties of Fibonacci quasi-periodic one-dimensional photonic crystals (1DPCs) containing superconducting material are theoretically investigated based on the transfer matrix method. It is shown that the 1DPCs can possess a same photonic band gap property as the periodic structure superconducting PC. The results of transmittance spectra show that the cutoff frequency can be manipulated through the thicknesses of the superconductor and dielectric layers as well as the ambient temperature of the system. It is observed that the shift of cutoff frequency becomes more noticeable by adjusting the thickness of the superconductor layer than that of the dielectric one. Furthermore, the cutoff frequency becomes very sensitive when the system temperature is tuned to close vicinity of the critical temperature of the superconductor.     

Analysis of Circular Dielectric Waveguide with Chiral Cladding

The propagation characteristics of a circular dielectric waveguide with chiral media filled in the cladding are investigated. The relation between the cutoff frequency and the chiral admittance, the dispersion curves for some modes with different angular mode numbers and the transverse distribution of fields are presented. Some new features different from the ordinary circular dielectric waveguide are resulted. The results show that the cladding chirality may lead to a single-mode operation in the circular dielectric waveguide.     

Design and analysis of a gallium lanthanum sulfide based nanoplasmonic coupler yielding 67% efficiency

In this paper, we propose a novel ultra-compact nanoplasmonic coupler using gallium lanthanum sulfide (GLS) which yields an efficiency of 67% at the optical communication wavelength. The analysis has been done numerically using the finite-difference time-domain method. Our proposed coupler can operate at a broad frequency range and easier to fabricate than couplers with multi-section tappers since it is a simple rectangular-shaped coupler with no variation along the whole length.     

Analysis of the spatial filter of a dielectric multilayer film reflective cutoff filter-combination device

The experiment setup of a reflecting combination device, which has more advantages than a transmitting combination device, is designed in this study. To achieve angular spectrum selectivity, only one type of reflective component is needed,so difficulties of design and preparation are reduced. A dielectric multilayer film is applied to the reflective component, and the long wave-pass coating stacks of the structure are designed. To achieve high stopband transmittance and reduce electric field intensity at a wavelength of 1053 nm, an objective function is proposed for designing an optimized coating. The final optimized coating has good spectral characteristics and a high laser-induced damage threshold. A dielectric multilayer film with high reflectance plays an important role in preparing and applying a dielectric multilayer film reflecting cutoff filter-combination device.     

Theory of negative-refractive-index response of double-fishnet structures

A theory is presented of the negative refractive index observed in the so-called double-fishnet structures. We find that the electrical response of these structures is dominated by the cutoff frequency of the hole waveguide whereas the resonant magnetic response is due to the excitation of gap surface plasmon polaritons propagating along the dielectric slab. Associated with this origin, we show how the negative refractive index in these metamaterials presents strong dispersion with the parallel momentum of the incident light.     

THE THEORETICAL INVESTIGATION OF THz ELECTROMAGNETIC WAVES IN A ROD DEGENERATE PLASMA-WAVEGUIDE

By using the Fourier components of dielectric tensor elements of cold collisionless degenerate plasmas, the dispersion relation of electromagnetic waves in a cylindrical metallic waveguide with a degenerate plasma column protected by an annular dielectric layer are obtained. The permissible frequency regions for slow and fast waves in E-mode (TM) are presented. Furthermore, the graph of cutoff frequency versus the radius of plasma column for the fast waves is investigated. In addition, the time growth rate for excitation of symmetric slow E-modes (TM) by a thin annular relativistic electron beam (TAREB) is studied. The graph of time growth rate respect to radius of dielectric layer and accelerating voltage are presented. PACS No. 52.25.     

Design and synthesis of a modified band-pass optical filter

The reflection and transmission coefficients of two-component and three-component dielectric multilayered periodic structures (2CODMS and 3CODMS) are derived using the transfer matrix method. The width of the high reflectance zone in the case of two-and three-component systems is derived and computed using suitable parameters. Numerical calculations for long-and short-wavelength cutoff band-pass filters of various structures are shown in a three-component system. Comparison is also done for 2CODMS for long-and short-wavelength cutoff filters. Spectral properties of interference reflection filters of the type [G(XY)A], whose components represent long-wavelength cutoff [X] and short-wavelength cutoff [Y], are also studied. The reflection and transmission bandwidth of the high reflectance zone is presented. Optimization is done in three-component systems to make it suitable for ideal long-and short-wavelength band-pass filters.