Numerical modeling of second harmonic generation in opticalwaveguides using the finite element method

A numerical study of second harmonic generation (SHG) in optical waveguides is presented using the finite element method (FEM) and the Crank-Nicholson split-step procedure. Results are given for a Cherenkov radiation scheme in both planar and channel waveguides. Also presented are results obtained on frequency doubling for guided modes in both planar and channel waveguides, using the quasi-phase-matching scheme     

Numerically efficient spectral domain approach to the quasi-TEManalysis of supported coplanar waveguide structures

A numerically improved technique for the quasi-TEM analysis of supported coplanar waveguides is presented. The spectral domain method is combined with a special set of basis functions, to facilitate an accurate and efficient solution. The resulting integrals are evaluated using closed-form expressions instead of numerical integration scheme which leads to short CPU time. In this study, numerical results for the characteristic impedances of coplanar waveguides are presented. Comparisons are also made between the computed results and available ones. The charge density distributions on the center signal strip as well as on the ground plane are examined     

A numerical study of erbium doped active LiNbO3waveguides by the beam propagation method

A numerical investigation of active waveguides realized on lithium niobate crystals using erbium as active element is presented. A software package is implemented to simulate the propagation of electromagnetic waves in graded-index active waveguides using an active vectorial beam propagation method (ABPM), which enables to calculate the optical field evolution along the propagation axis. A comparative study of the optical signal gain evolution as function of erbium concentration profiles obtained by various doping methods is presented. The optimal doping method, leading to the maximum gain, is determined     

A fast mode analysis for waveguides of arbitrary cross section with multiple regions by using a spectrum of two-dimensional solutions and asymptotic waveform evaluation

A fast mode analysis for waveguides of arbitrary cross section with multiple regions is presented in this paper. The analysis is based on a spectrum of two-dimensional (2-D) solutions with application of asymptotic waveform evaluation, which requires only several 2-D solutions in searching for the propagation modes and calculating the field distribution of the modes in waveguides. The boundaries of waveguides can be modeled by perfect electric conductors, perfect magnetic conductors, dielectric materials, and asymptotic strip boundary conditions. By this modeling, one can also analyze the waveguides with the soft and hard surfaces. The method is excitation dependent, which provides a tool to analyze the response of different modes to different excitations. No existence of spurious modes is experienced by using this method. The verification and comparison of the numerical results with analytical, published data, and measurements are also presented in this paper.     

Transmission and attenuation of the dominant mode in uniformly bentcircular hollow waveguides for the infrared: scalar analysis

A numerical evaluation is conducted of electric field distributions, phase constants, and attenuation constants of the lowest eigenmode in the general class of uniformly bent circular hollow waveguides. The analysis is based on a scalar equation, and numerical results are compared with those of existing approximate theories. Normalized forms of attenuation constants are presented for the parallel and perpendicular polarizations to the bending plane by using structural and material parameters. For sharply bent waveguides, useful and simple expressions are derived for the attenuation constants of the TE and TM modes in the corresponding slab geometry with suitable weighting parameters     

The novel boundary integral equation method for solving arbitrary cross-section waveguides

A novel method for solving arbitrary cross-sectionn waveguides is presented. The novel method is a modification of the eigen-weighted boundary integral equation method; the EWBIEM is modified by using the eigenfunction of a fictitious regular boundary as weighting function, whose eigenvalue may be the known value, and meanwhile using the domain-bases. To confirm the validity of the novel method, numerical analysis are presented for circular groove guide as an example.     

Finite Element Analysis Waveguides of Optical

A finite element program for the analysis of anisotropic optical waveguides is described. The appearance of spurious numerical modes, due to the fact that the functional is nonpositive definite is discussed and a possible solution to the problem is presented. For isotropic waveguides it is shown that both EH- and HE-type modes can be very accurately approximated by two different scalar finite element programs. Finally, a method for calculating the attenuation of leaky modes in a single material integrated optic waveguide using this scalar finite element method is proposed.     

基片集成波导带通滤波器的设计与实现

基片集成波导技术使得包括平面电路、接头和矩形波导在内的完整电路可以以平面形式集成在印刷电路板上;首先简要介绍基片集成波导这一新技术,然后把矩形波导带通滤波器的设计方法引入基片集成波导中,设计了一个中心频率为35 GHz,相对带宽为2.7%的基片集成波导带通滤波器,CST的数值计算结果显示该途径是成功的。     

Forming flat-topped element patterns in antenna arrays of two-mode waveguides

The results of numerical simulation are presented for an array of two-mode slot-coupled parallel plate waveguides excited by TEM modes through dominant mode waveguides and two-step junctions. It is shown that flat-topped element patterns formed by this simple structure are no worse than those of a known array with power dividers and directional couplers.<>     

圆形槽波导的一种简单分析方法

把圆形槽波导等效成横向传输线网络,用不同的均匀传输线等效圆形槽及两边的平行平板区域,根据横向谐振条件,利用Runge-Kutta数值计算方法,分析了波导的色散关系.得到了归一化截止波长λc/2a与归一化波导尺寸2c/2a,以及传播常数β与频率的关系曲线.该分析过程简单明了,数值分析的结果与相关文献的结论吻合较好,表明这...     

圆波导结构中TM0和TE0模式传输特性的时域分析法

本文提出了一种适合于求解各类复杂圆波导结构ＴＥ０和ＴＭ０模式的截止频率和色散曲线的ＦＤＴＤ分析方法，并可在一维空间中加以处理，大大提高了计算效率和减少了存贮量。本文对圆波导中ＴＥ０和ＴＭ０模式的截止频率和色散曲线进行了计算和分析，同时分析了网络剖分对计算结果精度的影响，并与已知的理论结果进行了比较，证实了这一方法的可靠性。作为实例，计算和分析了表面波圆波导结构的色散曲线，所得结果与实验结果和其它数     

Calculation of the fundamental mode sizes in optical channelwaveguides using Gaussian quadrature

A fast numerical method using Gaussian quadrature, which takes only seconds on a microcomputer, is presented for calculating the fundamental mode sizes in optical channel waveguides. Variational expressions for the square of the propagation constant, β² , of the TE- and TM-like modes are derived using the vector wave equations. For channel waveguides with gradual refractive index distributions, these expressions approach the variational expression obtained using the scalar wave equation. To show the usefulness of the numerical technique the authors present the results for titanium indiffused lithium niobate channel waveguide which are commonly used in integrated optical circuits. Since these waveguides have gradual refractive index distributions, both types of expressions give the same results; however, it takes less time to compute the mode sizes when using the variational expression obtained from the scalar wave equation. The authors find the calculated mode sizes are in good agreement with published measurements. From the comparison process, best fit parameters are obtained, which give mode sizes close to the values published in the literature. For one special case the authors are able to obtain an analytical variational expression and they use it to test the accuracy of the numerical method. They find that the values of β² given by both methods agree to six significant figures     

Coupling tolerances of high-index silicon-oxynitride waveguides with small bending radii

Silicon-oxynitride waveguides gained by plasma-enhanced chemical vapour deposition are very attractive for the fabrication of passive optical components used in optical networks. The low-loss and compact devices with small bending radii are achieved with a new high-index waveguide design. At the same time this feature increases the requirements on the fibre-to-chip coupling compared to common fibre-matched waveguides. In this paper, we discuss the junction of the high-index optical components to fibre systems and their coupling tolerances. The presented solution is based on using high numerical aperture fibres. Furthermore, the option of higher automation and reliability is given by the coupling with tapered fibres because they allow better positioning tolerances.     

最小二乘边界配点法在电磁场边值问题数值分析中的应用

进行了最小二乘边界配点法在电磁场边值问题数值分析中的应用研究。对ＴＥＭ传输线和波导本片值等问题进行了计算，计算结果与其它方法的计算相结果吻合。应用ＬＳＢＰＭＭ进行电磁场边值问题数值分析有概念明确，占用计算机内存少、节省机时和使用方便等优点。     

Vector finite element solution of saturable nonlinear strip-loaded optical waveguides

A numerical solution is given for nonlinear optical waveguides with power confinement in both transverse dimensions. Self-consistent solutions are obtained by using an accurate vector-finite-element formulation along with the penalty technique. Numerical results for the first quasi-transverse-magnetic power-dependent mode are presented for strip-loaded waveguides with saturable self-focusing media. The variations with total power are illustrated for the modal index and for the fraction of the total power carried by different regions, showing interesting abrupt power switching for realistic geometries. It is shown that the switching effect is maintained in the presence of saturation and over a range of two-transverse-dimensions geometries. This switching effect can be controlled with variation of some of the parameters of the guide.<>     

A field-based numerical method for three-dimensional analysis of optical waveguide discontinuities

A field-based numerical method for simulation of field scattering at discontinuities along three-dimensional optical waveguides of arbitrary index profiles is presented. Different from the previous work based on directly diagonalizing the characteristic matrices, we developed a robust and efficient iterative scheme by using an improved Neumann series. Superb performance of the scheme in terms of accuracy and efficiency is demonstrated and verified.     

Analysis of Open Dielectric Waveguides Using Mode-Matching Technique and Variational Methods

The mode-matching technique is employed for computing the propagation constants and field distributions of an inverted strip dielectric waveguide. The results derived in this manner are further improved by using variational formulas expressly designed for open dielectric waveguides. Illustrative numerical results are presented and compared with an experimental measurement as well as those based on approximate methods found in the literature.     

Diffraction of electromagnetic waves by the interface of two isotropic planar waveguides

The problem of excitation of the rectilinear interface of two semiinfinite planar waveguides by an eigenmode of one of these waveguides incident onto the interface at an arbitrary angle is considered. Planar waveguides shaped as a dielectric plate coated by thin isotropic films (e.g., gratings with spacings small as compared to the wavelength) are analyzed. A model of this structure in which films are described by means of two-sided impedance boundary conditions and parameters of the planar waveguide are varied by varying the film impedance is constructed. Solution to the electromagnetic problem by the Wiener-Hopf technique is presented. Closed-form expressions for scattering parameters of the analyzed structure are obtained. Results of the numerical solution are presented. Comparison with available results obtained for particular values of the film impedance is performed.     

Enhancement of power transfer in periodic array of optical waveguides via intermediate Bloch states

A directional coupling mechanism between different waveguides in a periodic array of waveguides is suggested. The optical power transfer between two different waveguides is mediated by the coupling between zero-order modes of two of the waveguides and the second band of the periodic structure. Analytical solutions for the no-detuning (narrow band) and far-from-resonance cases are presented. The far-from-resonance case is shown to resemble a simple two-mode system with complete optical power transfer between the two waveguides, coupled by localized gratings. The transfer is mediated by the second band of the periodic structure. The transition length depends strongly on the shape of the perturbation, and depends exponentially on the distance between the waveguides, yet it allows us to transfer power from one waveguide to another at such distances, for which the transition via conventional directional tunneling mechanism is impossible. Our analytical results are supported by numerical calculations carried out for a model problem with realistic parameters.     

Computer-aided design of E-plane waveguide passivecomponents

The newly developed numerical analysis method for the inductive discontinuities in rectangular waveguides is presented. It can be used to analyze the scattering properties of E-plane uniform conductor-dielectric inserts in rectangular waveguides. These inserts are of arbitrary cross section and number. The calculation accuracy and speed are improved by a combined analytical-numerical approach. Some practical applications are given demonstrating its engineering usefulness