A comprehensive Auxiliary Functions of Generalized Scattering Matrix (AFGSM) method to determine bandgap characteristics of periodic structures

A comprehensive Auxiliary Functions of Generalized Scattering Matrix (AFGSM) method is presented on the bandgap analysis of periodic structures encountered in many engineering applications. Proposed method accurately determines the bandgaps of periodic structures with symmetric and asymmetric unit cells. In order to test the feasibility of the proposed method, numerical results are compared with Eigenvalue method (EIV) and HFSS/CST frequency domain simulations. The validity and applicability of the presented method are demonstrated by analysing the bandgap characteristics of periodically dielectric loaded rectangular waveguides, photonic crystals, helix Slow Wave Structures (SWSs) of Traveling Wave Tubes (TWTs) and excellent agreements on the simulation results are obtained. Bandgap analysis and design of different periodic structure problems can be effectively achieved using the proposed AFGSM method.     

A fast and accurate design method for broad omnidirectional bandgaps of one dimensional photonic crystals

A fast and accurate novel design method is proposed for the design of broad omnidirectional bandgaps of one dimensional (1-D) photonic crystals (PCs). Presented method is verified with various numerical examples for 1-D photonic crystals which consist of a cascade of two quasi-periodic stacks and broad omnidirectional bandgaps are achieved. Furthermore, computation time requirement of the presented method is considerably less than that required for purely numerical approaches. The proposed algorithm is quite flexible and can easily be modified to address problems involving 1-D PCs consisting of three and more cascaded stacks and specific 2D PC structures.     

周期数对一维光子晶体带隙的调制研究

利用特征矩阵法,研究了光波正入射到光子晶体时,一维光子晶体的带隙结构随周期数的变化。结果表明,对于不含缺陷层的光子晶体,随着光子晶体周期数的增加,光子晶体的带隙宽度变化不大,而带隙率变化明显。对于含缺陷层的光子晶体,在缺陷层两侧周期数相同时,周期数的增加使得光子晶体的"光谱挖孔"效果明显;在其两侧周期数不同时,只有在两边周期数接近时"光谱挖孔"才有一定的效果。     

一种新型一维微带PBG单元结构

通过对传统二维微带 PBG 结构的研究,针对微带线的传播常数是微带线相对于接地板上周期孔眼的两个主轴的位置和方向的敏感参数而不能根据实际情况任意布线的缺点,提出了一种新型一维微带 PBG(photonic bandgap)单元结构及其等效 L-C 电路模型。本文提出的 PBG 传输线可以应用于微波集成电路中,能够减小电路尺寸,且可以抑制高次谐波的产生。     

2-D Direction-of-arrival Estimation of Real-valued Sources

A new method is presented to estimate two-dimensional （2-D） Direction-of-Arrival （DOA） angles of narrowband real-valued signals impinging on a L-shape Arrays（LA）. The basic idea of the proposed method is to increase both the effective aperture size and the number of sensors by employing the conjugate invariance property of real-valued signals. Thus, the proposed method can provide a more precise DOA and detect more signals than the Cross-Correlation Matrix Method （CCMM）. Numerical simulation results are presented to support the theory.     

矩形波导中左右手材料光子晶体的色散特性研究

研究了在矩形波导E平面填充的一维周期或准周期左右手材料光子晶体中电磁波的色散特性.采用传输矩阵法推导出一种适用于任意一维光子晶体E面填充矩形波导的2×22×2阶特征矩阵.定量分析了周期光子晶体中单元结构的重复次数、光子晶体的排列方式(周期,斐波那契,Thue-Morse和Octonacci排列)、及左手/右手材料介电常...     

Applications of Self-Collimated Properties of Photonic Crystal in 3D Imaging Lidar System

Photonic crystals(PCs)are increasingly attracting attention due to their ability to control light propagation.In this paper,the dispersion properties of a two-dimensional(2D)square lattice PCs with plane-wave expansion(PWE)method are presented,the equi-frequency contours and the band structure are analyzed,and the alignment transmission characteristics are simulated by using the finite difference time domain(FDTD)method,in addition,for the wavelength of 1.55μm,a kind of application structure with the lattice constant a=405nm and the radius of air holes R=135nm which can restrict the transmission of beams in photonic crystal without defect is proposed and simulated.The structure which can collimate the output beam and compress its divergence angle is easy to design.It has wide application prospects in optical communication and three-dimensional(3D)imaging lidar systems.     

Full-wave design and realization of multicoupled dual-mode circularwaveguide filters

A new full-wave method for the design and realization of dual-mode circular waveguide filters is presented. The rigorous CAD is a combination of the mode-matching and the finite-element techniques, which permits obtaining the Generalized Scattering Matrix for all the blocks that compose the structure (rectangular slots, cross-irises, and screws). The finite thickness of the irises, the higher order mode interaction, as well as the coupling and tuning screws are rigorously taken into account. A systematic design process for the different elements is described. A full prediction of resonant out-of-band spurious modes is accomplished prior to the filter construction. Special attention is devoted to the circuital model in order to save a great deal of computational effort in the final adjustment. A four-pole elliptic circular waveguide cavity filter has been designed and constructed. The experimental filter results show excellent agreement with theory     

介电常数对比和填充率对光子晶体中光子禁带和局域态的调节

用有限时域差分法(FDTD)和Padé近似分析了二维光子晶体的能带结构和缺陷引起的局域态.针对介电常数对比和填充率对完整光子晶体中光子禁带以及缺陷态的影响作了研究.计算了不同缺陷的光子晶体模式的振荡频率和质量因子.数值模拟的结果表明通过改变介电参数对比和填充率可以实现对光子禁带的位置、宽度、数目以及对缺陷态的调整.     

A novel method for designing one dimensional photonic crystals with given bandgap characteristics

A novel method is presented for determining the dimensional parameters of one-dimensional (1-D) photonic crystals (PCs) with specified bandgap characteristics. Conventionally, the bandgaps are determined by solving an eigenvalue equation on a fine frequency mesh. This approach requires considerable computation time and is therefore not suited for use in the optimization cycles needed in dimensional design.     

1维微纳米周期结构的散射测量建模

为了研究散射测量的正向测量依据,采用严格耦合波分析理论,对1维矩形面型周期性结构衍射建模,在MATLAB环境下实现严格耦合波分析算法,并讨论了1维周期结构高度、线宽和占空比的测量特性,理论上线宽的测量可以达到纳米级分辨率。结果表明,严格耦合波分析理论精确和高效,对1维微纳米周期结构表现出了良好的测量特性。这为散射测量提供了科学性和可行性依据。     

用特征散射方向图预估电大平面阵的散射

利用平面照射波在无限大周期阵列上感应电流的周期特性，对无限阵列格林函数加窗的方法得到了有限阵列的格林函数，从而将电大有限阵列的分析缩减到单个的阵元上。进而由矩量法得到单个阵元上的电流分布和散射场，并定义为单元的特征散射方向图。仿照阵列综合理论，整个阵列的散射归结为特征散射方向图和阵因子的乘积，极大的简化了电大有限阵列的散射分析，并通过算例验证了该方法的有效性。     

Electric field distributions of waveguide arrays for local tumor hyperthermia

Total electric field distributions in muscle and fat tissues, due to colinear rectangular waveguide arrays at 2.45 GHz and 915 MHz were calculated. The effect of phase difference between incident phases on the field pattern is shown. Phase adjustment is capable of furnishing control of either field-size or focused-field performance of the multi-element, direct-contact applicator. The tissue-applicator junction is analyzed by means of the Generalized Scattering Matrix (GSM) of the generalized 2-port discontinuity, assuming that the lossy homogeneous tissue is immersed in a large waveguide. This method provides an exact calculation of multimodal fields, as well as reflection and coupling coefficients in the apertures.     

Size Reduction of Mushroom-Type EBG Surfaces by Using Edge-Located Vias

Periodic surfaces made of patches with metallized via holes or grounding pins (ldquomushroomsrdquo) have been shown to have bandgaps in their dispersion diagrams, inside which surface waves cannot propagate. These bandgaps are defined in all directions in the surface structure. The purpose of this work is to show how by changing the position of the metallic via of the mushroom from its center to its edge, the bandgap moves towards lower frequencies. This allows an easy structure size reduction which is critical in many applications. Results prove a size reduction of the unit cell size by approximately 20% by only moving the via position. The conclusions have been validated with measurements.     

Scattering of surface magnetostatic waves by periodic slot gratings

Scattering of the magnetostatic surface waves generated in thin films by the gratings formed from slots in a metal screen is theoretically analyzed. A boundary-value problem for the Maxwell equations is formulated and solved in the static approximation. An algorithm of numerical solution of the boundary-value problem is proposed. Scattering of magnetostatic surface waves by 2D periodic slot gratings that are infinite along one coordinate and finite along the other coordinate is studied for an arbitrary orientation of slots and an arbitrary angle of incidence of the magnetostatic wave. The band structure of gratings is studied. The possibility of formation of magnonic crystals based on slot gratings is demonstrated.     

Application of Photonic Crystals in Semiconductor Lasers

Photonic crystals(PCs) have attracted much considerable research attention in the past two decades. They are artificially fabricated periodic dielectric structures. The periodic dielectric structures have photonic band gap(PBG) and are referred to as photonic band gap materials. This paper mainly introduces one-dimensional (1-D) and 2D PCs applied in the semiconductor lasers.     

Photo-Responsive Azobenzene-Containing Inverse Opal Films for Information Security

Stimuli-responsive photonic crystals (PCs) have attracted increasing attentions owing to the unique optical feature in regulating the propagation of light and tunable structural colors in response to external stimuli, emerging application potential on diverse fields. However, the development of stimuli-responsive PCs with wide visible light range, broad shift of bandgaps, and adjustable responsive rates for counterfeiting remains challenging. Herein, a simple strategy for the preparation of photo-responsive azobenzene-containing inverse opal (AzoIO) films is reported. First, azobenzene-containing composites are generated by filling functional monomers into voids of silica colloids crystals. Followed by the thermal polymerization and subsequent etching, a series of AzoIO films are successfully fabricated with adjustable structural colors in wide visible wavelength. Upon irradiation with linearly polarized visible light (LPVL), a slowly broad blueshift of bandgaps (≈138 nm, 3200 s) is observed due to the anisotropic shrinkage of the periodic PC structures. However, UV light irradiation contributed to a fast broad blueshift of bandgaps (≈131 nm, 10 s), owing to the photoisomerization merit of azobenzene moiety. The proof-of-concept study on the applications in light-modulated multicolored writable paper, encryption films, and fast writing/erasing demonstrated the potential for information security. This work paves an avenue for developing promising optical anti-counterfeiting materials.     

一种新型一维周期DGS单元结构特性研究

该文设计了一种新型一维周期地面缺陷(Defected Ground Structure, DGS)单元结构,该DGS单元结构提高了等效电感。增加的等效电感可以容易控制DGS平面电路的截止频率特性。设计的周期DGS单元结构有非常好的截止和带阻特性。为了显示改进的等效电感,该文设计了3个周期相同而单元尺寸不同的DGS电路。DGS电路的测试结果显示截止和带阻的中心频率特性由该DGS单元结构的物理尺寸决定。     

Bandwidth Enhancement for SSN Suppression Using a Spiral‐Shaped Power Island and a Modified EBG Structure for a λ/4 Open Stub

This paper proposes a spiral‐shaped power island structure that can effectively suppress simultaneous switching noise (SSN) when the power plane drives high‐speed integrated circuits in a small area. In addition, a new technique is presented which greatly improves the resonance peaks in a stopband by utilizing λ/4 open stubs on a conventional periodic electromagnetic bandgap (EBG) power plane. Both proposed structures are simulated numerically and experimentally verified using commercially available 3D electromagnetic field simulation software. The results demonstrate that they achieve better SSN suppression performance than conventional periodic EBG structures.     

Scattering of volume magnetostatic waves by periodic slot lattices

Scattering of volume magnetostatic waves excited in thin films by the lattices composed of metal ribbons and slots in a metal screen is analyzed. A boundary value problem for the Maxwell equations is formulated and solved in the static approximation. An algorithm for the numerical solution of this boundary value problem is proposed. Scattering of volume magnetostatic waves by 2D periodic lattices of slots that are infinite along one coordinate and finite along the other coordinate is studied for an arbitrary orientation of slots and an arbitrary angle of incidence of the magnetostatic wave. The energy-band structure of lattices is analyzed. The possibility of formation of magnon crystals based on the slot lattices is demonstrated.