Periodic structures with time-varying loads

The loading of a periodic surface with time-varying negative resistance diodes is discussed. The method predicts the transmitted and reflected power at the source frequency and the harmonic frequencies generated by the time-varying devices. The analysis uses an equivalent circuit representation at the load location in the unit cell, which is derived from the moment method solution of the periodic problem. It is therefore applicable to all angles of incidence, arbitrarily shaped surfaces, arbitrarily placed loading, lossy conductors, and surfaces supported by dielectric layers     

Periodic waveguide structures with long cells

In this paper, a class of periodic waveguide structures with stepwise constant circular cross section is analyzed by means of Hahn's method of modal field matching along transverse planes. It allows one to resolve algebraically the implicit determinant relation between the phase shift per cell and frequency and to obtain an explicit formula. Dispersion diagrams and field distributions are also calculated and plotted and convergence properties of the method are tested     

Periodic structures prepared by two-beam interference method

We present an optical interference method as the efficient tool for high-quality one- (1D) and two-dimensional (2D) periodic structure fabrication. Different types of 2D periodic structures are prepared using two-beam interference technique by double exposure. Also, the patterning of Au layer is provided using two-beam interference method. Quite homogeneous 1D and 2D structures with small periodicity were prepared in photoresist and Au layer. The experimentally prepared structures are well in agreement with the theoretically designed ones. According to experimental results, we favor two-beam interference technique using multi-exposure process as a very useful method for fabrication of 2D periodic structures and devices for integrated optoelectronics.     

Periodic slow-wave low-loss structures for monolithic GaAs microwave integrated circuits

Slow-wave structures on GaAs semi-insulating substrate, obtained by periodically loading a coplanar line with high-Q overlap capacitors, are described. They operate up to X-band, reducing significantly the signal phase velocity by a factor nearly independent of the frequency. Owing to their low transmission losses, they are particularly suitable for monolithic GaAs f.e.t. circuits.     

Description and simulation of physical effects in chiral guiding structures

Methods of mathematical simulation of chiral guiding structures are considered. A rectangular chiral waveguide is calculated with the use of the mixed-finite-element method. For a plane-parallel waveguide with a chiral filling, the fields are obtained on the basis of an analytic solution via the finite-difference method.     

Periodic structures on coupled slot resonators in the grounding layer of microstrip transmission line

The spectrum of natural frequencies of the resonator has been calculated. The specified resonator includes a microstrip transmission line with discontinuity in the form of two rectangular coupled slot resonators in the grounding layer. Based on the above spectrum and using the transverse resonance method the scattering matrix of the principal wave of the microstip transmission line on this discontinuity was calculated. The scattering characteristic of the periodic structure consisting of a finite number of cells in the form of coupled slot resonators in the grounding layer of microstrip line indicates that with due regard for their mutual coupling the losses in the first stopband can be reduced by 3–5 dB as compared with the characteristic obtained by tandem connection of the scattering matrices of separate slot resonators in the grounding layer of microstrip line.     

Periodic structures on biconically tapered optical fibers using ion beam milling and boron implantation

In this paper, the authors introduce local periodic perturbations of the cladding refractive index in the reduced diameter (waist) region of biconically tapered single-mode optical fibers by two methods. The first was focused ion beam milling to give short grooves perpendicular to the fiber axis, and the second was boron implantation, giving a phase grating in the cladding. Both structures exhibit a wavelength-dependent throughput and are highly sensitive to the environment in the waist region, which makes them potentially applicable in optical communication networks as well as in sensors. A simple corrugated slab-waveguide model is able to account for the measured spectral transmission of these structures.     

The exponent of the field singularity at the edge of structures formed by sectors of mirror-conjugated chiral media

The method of the second-order characteristic matrix is proposed for determining the exponent of the electromagnetic-field singularity at the edge of open wedge-shaped chiral structures formed by sectors of alternating mirror-conjugated media. The dispersion of the singularity exponent as a function of the chirality parameter is investigated analytically, and the dependence of the exponent on the number of sectors and the structure configurations is studied.     

Effective electromagnetic and chiral parameters of chiral composite material

The effective parameters of chiral composite are studied using a simple model, that is, randomly oriented non-interacting wire helices embedded in a nonchiral host medium. It is found that both the effective permittivity ? and permeability μ are independent on the handedness of the chiral objects while the effective chirality admittance ξ is dependent. It is also found that when the ratio of the radius of the chiral helix to its pitch is about 0.23, maximum chirality admittance is achieved. The effective parameters of equichiral sample are also discussed.     

周期性谐振腔的稳定性

详细分析了一般周期性谐振腔的稳定性，发现对一每周期合ｍ根激光棒的Ｎ周期谐振腔，共存在ｍ个稳定区，并在每一稳定区内存在（Ｎ—１）个奇异点，在这些奇异点处，谐振腔处于介稳状态，对失周期性很敏感；另外，还讨论了周期性谐振腔的热稳条件问题。     

Periodic multielement strip gratings

A method of analysis for strip gratings with more than one conducting strip per period is given. The method is then applied to a periodic twin-strip grating with two unequal gaps. The scattering parameters are found from a set of linear equations which may be solved numerically.     

Periodic receiving broad-band antenna arrays

The principle of the periodic receiving antenna array composed of arbitrary antenna units has been developed. A generalization of the well-known principle of log-periodic antennas is presented and applied also to antenna units formed by the system of dipoles with active networks. This reveals the potentialities for the exploitation of this principle in the miniaturization of directional antenna systems.     

周期相位调制光束的放大

为研究周期相位调制光束的放大特性,在分析激光放大介质跃迁谱线线型对损耗、受激辐射截面及饱和能量密度等参量影响的基础上,改进了原先的脉冲放大模型。以Nd∶YLF放大器为例,实验中获得的时间波形调制周期约为300ps,与计算结果330ps吻合较好;同时依据该模型计算分析了影响放大输出时间波形的主要因素,入射光场中心频率与跃迁谱线中心频率的匹配能有效降低相位调制-振幅调制(PM-AM)效应,为抑制该效应提供了依据。     

Theory of Periodic Dielect Waveguides

The propagation of electromagnetic waves along open periodic, dielectric waveguides is formulated here as a rigorous and exact boundary-value problem. The characteristic field solutions are shown to be of the surface-wave or leaky-wave type, depending on the ratio of periodicity to wavelength (d/lambda). The dispersion curves and the space-harmonic amplitudes of these fields are examined for both TE and TM modes. Specific numerical examples are given for the cases of holographic layers and for rectangularly corrugated gratings; these show the detailed behavior of the principal field components and the dependence of waveguiding and leakage characteristics on the physical parameters of the periodic configuration.     

Stress-Aware Periodic Test of Interconnects

Journal of Electronic Testing - Safety-critical systems have to follow extremely high dependability requirements as specified in the standards for automotive, air, and space applications. The...     

周期性结构的边缘元分析

本文用边缘元、模匹配以及多模网络相结合的方法分析周期性结构。计算了ＮＲＤ波导周期结构和介质镜象线周期结合两个具体实例。数值结果表明这种方法用于分析周期性结构不仅是有效的，而且上仍很高的计算精度和效率。     

Image theory for chiral bodies

Image theory for a chiral body over a perfect electric or magnetic conducting ground plane is developed using the chiral volume equivalence theorem and conventional image theory for electric and magnetic currents. It is shown that the image of the chiral body has the same material parameters as the original body, except that the chirality admittance of the image is the negative of the original. In essence the mirror image of a chiral object is that object, such as a helix, with the opposite handedness. Alternatively, the same results can be obtained using tensor analysis     

Homogenisation of densely-distributed chiral spheres

A homogenisation theory for densely-distributed chiral spheres is developed by introducing the concept of quasicrystalline approximation with coherent potential. Coherent interaction of the inclusions is taken into account. Numerical results for the effective propagation constants are presented     

Uniaxial chiral quarter-wave polarisation transformer

The uniaxial chiral medium is a generalisation of the well-studied isotropic chiral media. It is obtained when microscopic helices with parallel axes are positioned in a host dielectric in random locations. Solutions for the dispersion equation and for the eigenwaves for a uniaxial chiral medium were recently found. Here the authors consider the polarisation properties of a transverse wave propagating through a uniaxial chiral slab. The results give a simple possibility for constructing a polarisation transformer for changing the polarisation of a propagating plane wave.<>     

Consideration of chiral optical fibres

Circular birefringence is a property of chiral materials. In this work, we consider the use of chiral materials in optical fibres to produce circularly birefringent optical fibres and in fibres where a contrast in circular birefringence contributes to forming the waveguide. (-)-menthyl methacrylate is also investigated as a possible material for the fabrication of such fibres.