Dispersion characteristics of complex refractive-index planar slab optical waveguide by using finite element method

In this paper, finite element method (FEM) mode analyses of planar slab optical waveguide having complicated refractive index profile are presented. We try to estimate the dispersion graph, mode cut-off condition, group delay and waveguide dispersion for the case of α-power and chirped-type refractive index profile. In order to obtain the more accurate result, we have derived the higher-order polynomial, which establishes the suitable relationship between b and V for different profile of optical waveguide. On the basis of the derived polynomials, the waveguide dispersion is analyzed for different type of refractive index profile waveguide. Our study shows that the waveguide dispersion can be substantially reduced when we deployed the optical waveguide having linearly chirped-type refractive index profile. Earlier too, the arbitrary refractive index profile has been analyzed but to the best of our knowledge chirped-type refractive index profile has not been analyzed till date for the case of planar slab optical waveguide.     

X-ray focusing within a single-crystal waveguide under grazing-incidence diffraction conditions

X-ray-beam propagation through a parallel-plate waveguide is investigated with allowance for grazing-incidence Bragg diffraction at the crystalline structure of the plates. Expressions for the waveguide modes are derived. It is demonstrated that undamped waveguide modes exist at angles exceeding the critical value (total external-reflection angle), thereby making it possible to increase the angle of capture of radiation incident on the waveguide. The calculated output intensities of the waveguide are compared with the waveguide-mode intensities in absence of grazing-incidence diffraction in the waveguide material.     

星形光波导耦合器的耦合特性分析

根据TE0模光波导的本征场分布、瑞利索末菲标量衍射积分公式和激励源与光波导耦合的匹配效率公式,给出光波导端面衍射和耦合的归一化发射系数和接收系数计算公式,推导出光波导端面非接触耦合的耦合效率计算公式。光波导模场分布采用高斯函数近似表达,给出简洁的计算光波导端面非接触耦合的耦合效率函数表达式。最后,基于星形光波导耦合器结构参量的特点,将累加运算采用积分运算近似表达,给出星形光波导耦合器接收光波导总的接收效率与耦合器基本参量的关系,阐明了星形光波导耦合器的耦合特性。     

Sound propagation in two-dimensional waveguide with circular wavefront

Sound propagation through a waveguide is generally modeled by the Webster horn equation which assumes a planar pressure wavefront. However, most of the sources are non-planar in nature. In this work, a 1-D model is derived for sound propagation through a 2-D waveguide with circular wavefront. The model is derived from the 2-D Helmholtz equation using the weighted residual method. The model assumes a uniform pressure across the angular coordinate at a given radial distance. A 2-D finite element model is used to validate the results for different waveguide geometries and it shows good agreement.     

Dispersion Characteristics of Waveguide Arrays in Optical Spectrum Analyzers

Formulas for calculating the spectral characteristics of waveguide arrays, which are incorporated into waveguide spectrum analyzers based on planar waveguides, channel waveguides, and fiber optical waveguides, are derived taking into account the contribution of both the waveguide dispersion and the material dispersion to the dispersion factor. These formulas are used to study the dependence of the dispersion factor on the waveguide-system parameters for specific models of waveguide arrays. It is shown that consideration of contributions of the waveguide dispersion and material dispersion can affect profoundly the spectral characteristics of waveguide arrays.     

外开槽同轴波导传播特性

 根据满足边界条件的一系列电磁场方程,采用场匹配法,详细推导了外开槽同轴波导的特征方程。在外开槽同轴波导光滑内同轴半径等于零的情形下,即变成外开槽圆波导,得到其特征方程。数值模拟了外开槽同轴波导及外开槽圆波导中TE₀₁模式的传播特性,得到了不同尺寸外开槽同轴波导开槽间隙半张角和槽深与特征根的变化关系。结果表明:开槽越深,间隙半张角越小,特征根值越小。     

梯形截面介质光波导的模吸收损耗

本文运用微分法由梯形截面介质光波导的近似模方程导出了模吸收损耗系数的公式.并结合计算实例进行了误差分析.     

任意截面光波导的模式计算

提出了一种计算近理想形状任意截面光波导模式特性的方法。首先运用微扰理论计算出光波导的电磁场分布,然后从麦克斯韦方程出发推导出一个计算光波导传播常数的公式并由此得出其色散曲线,该方法没有繁杂的计算过程。     

Catastrophes and phase hysteresis in an optically nonlinear corrugated waveguide

Special features of propagation of light in a nonlinear corrugated optical waveguide were studied in relation to the control parameters. The phase hysteresis in the waveguide is studied, and the expressions for the phase jumps resulting from the state switching are derived.     

内外开槽同轴潘尼管波导传播特性

 推导了内外开槽同轴波导和外开槽圆波导的特征方程。数值模拟了内外开槽同轴波导及外开槽圆波导中2π模式的传播特性,研究了开槽深度与截止波数的关系及内外开槽潘尼管频率与各个半径之间的关系。结果表明：内外开槽同轴波导的特征值随内开槽深度的增加而增大,随外开槽深度的增加而减小;内槽半径对频率的影响很小,外槽半径起主要作用。     

Ray-optics analysis of the coupling efficiency from a gaussian beam to a rectangular multimode embedded strip waveguide

The modified ray-optics method is used to analyze the coupling efficiency from a Gaussian beam to a rectangular multimode embedded strip waveguide. It is convenient for analyzing the case of a simple waveguide structure because of reduced computation time. The conditions for determining which optical rays can be coupled into the waveguide to become the waveguiding modes, as well as the effective receiving area of the waveguide, are derived in this work. The data obtained by this method are compared with those calculated by the well-known overlap integral theorem and Marcatili's models for investigating the validity of the modified ray-optics method.     

全电极脊形波导光传输特性

给出一种较为简便的全电极脊形波导的分析方法,即采用有效折射率方法把此金属包层脊形波导化成一个二维等效平板波导,然后利用微分法得到模的有效折射率满足的方程和吸收损耗系数的解析表达式.作为一个特例,用这种方法对SiO2全电极脊形波导光传输特性如光传播常数和损耗进行了计算, 并得到一些有益的结论.     

Existence of negative dispersion and band gap in a helically inner cladded annular circular waveguide

Helical waveguide, a different type of waveguide structure, has been considered for analysis of modal dispersion characteristics. This paper deals with the study of a new type of annular waveguide, in which the inner cladding is made by the helical windings i.e. sheath helix and the outer cladding is as usual simple step-index cladding. Using vector approach, the general characteristic equation for the proposed waveguide has been derived. The modal dispersion characteristics for the lowest order modes for different pitch angles and thickness are determined and analyzed. We have found that there is an existence of the negative dispersion curve in the helically inner cladded annular circular waveguide. It means that the inner cladding is responsible for the negative dispersion which is generally obtained in a photonic band gap.     

基于复数电压分布的波导缝隙天线的改进设计

 针对波导缝隙阵列,提出了一种基于复数电压分布的改进的波导缝隙阵列天线的设计方法。 针对Elliott 对于波导缝隙阵列的设计只适用于实数的电压分布,从而不能设计出有任意形状的方向图的天线的问题,对此方法进行了改进,将其扩展到了任意的复数电压分布,并且考虑了缝隙之间互耦的影响。最后,利用改进的方法设计了一个有16个缝隙的端馈线阵方向图,与商业软件Ansoft HFSS的仿真结果比较,证明了方法的有效性。     

Waveguide invariance structure for low frequency monostatic bottom reverberation mitigation in shallow water

The stable range-frequency interference structure(waveguide invariance) of the low frequency monostatic bottom reverberation in shallow water is derived theoretically in this paper by using ray-normal mode coherent reverberation model and separable bottom scattering model.And combined the concept of spectral subtraction,a reverberation forecasting and mitigating method based on the waveguide invariance is presented.According to the waveguide invariance,the reverberation intensity for a detecting range can be estimated from the reverberation returns scattered from some other range cells nearby the detecting range with frequency shift.Then the reverberation component for the detecting range in the echo can be canceled mostly by using the estimated reverberation intensity,so as to enhance the echo-to-reverberation ratio and improve the detection capability of the active sonar.Simulations in typical horizontal layered shallow water environment show the stability of waveguide invariance structure in the low frequency monostatic bottom reverberation and the efficiency of the reverberation forecasting and mitigating method based on the waveguide invariance.     

太赫兹波段折叠波导行波管的线性分析和计算

给出了太赫兹波段折叠波导行波管中考虑管壁欧姆损耗的带电子束扰动的色散方程。求解该方程可以得到器件中小信号增益的值。通过编制Matlab程序,分析计算了不同工作点、不同折叠波导结构参数和不同工作频段时小信号增益的变化特性。计算结果表明:适当选取工作点和结构参数,可以获得最佳增益值;考虑损耗后,除了前向增长的辐射场外,还会出现反向传输的静态波;随着工作频段向高频方向延伸,前向波的增益显著降低,而反向波强度则增大。因此,工作频率提高时,为了达到一定大小的增益,需要的折叠波导的周期数也相应增加。     

On the theory of transition radiation in a waveguide

The transition radiation from a particle that intersects the waveguide perpendicular to its axis is considered. The expressions are derived for the radiation fields and intensities. The example of a rectangular waveguide is used to investigate the properties of the radiation, and the conditions which determine the Vavilov-Cerenkov radiation spectrum are derived.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 15, No. 2, pp. 191–195, February, 1972.     

Lossy double negative guiding layer optical sensors

We proposed a three-layer waveguide as an optical sensor for homogeneous sensing applications. A guiding layer of the proposed structure is considered as lossy left-handed material (LHM) with simultaneously the complex negative electric permittivity ɛ and the complex negative magnetic permeability μ. We also assume a cladding layer to have an intensity-dependent refractive index. Sensitivity of the proposed optical waveguide sensor is derived and its dependence on different parameters of a waveguide is studied.     

EM Wave Propagation in Ferrite-Filled Transversely Magnetized Circular Waveguide

This paper presents a rigorous method of solving Maxwell's equations for ferrite-filled transversely magnetized circular waveguide. Solutions for cylindrical coordinate system are derived by using power series expansion of the field's potentials. Complex propagation constants are obtained by applying boundary conditions and representing fields in partial cylindrical modes. Plane wave representation of propagation is also considered. Numerical calculations of the propagation constants as well as the dominant waveguide mode reflection and transmission from a ferrite-filled waveguide section are presented.