Free space radiation mode analysis of rectangular dielectric waveguides

The free space radiation mode (FSRM) method is used to provide a new closed-form transcendental equation for the scalar mode propagation constant of a uniformly buried rectangular dielectric waveguide. Results are readily and rapidly obtained and are shown to be very accurate over the range of practical interest.     

Coupled mode analysis of light modulation in dielectric waveguides

A detailed analysis of electrooptic light modulation in optical waveguides is presented. Several important problems of a waveguide modulator, such as the difference of waveguide axes from crystalline electrooptic ones, the distribution of transverse and longitudinal field components of light modes, and the traveling-wave property of the modulating field, are discussed. The analysis is based on the coupled mode theory, regarding the modulation as the coupling among sidebands of unperturbed waveguide modes. The coupled mode equation is derived for the modulation in optical waveguides. It can be solved if the normal modes of the waveguide are given. Actually the equation is solved for the modulation in dielectric slab waveguides and the mechanism of modulation is discussed. The results of the analysis are applied to designing two types of waveguide modulators. In an example (10.6 μm modulator with a GaAs slab waveguide) a new efficient crystal orientation is found. The calculated phase retardation with this orientation is 0.13 rad/(V·cm) with a 1 μm thick slab. Another example of a 0.633 μm modulator using a LiTaO₃ crystal as a substrate is also described.     

Coupled-mode analysis of periodic dielectric waveguides

The coupled-mode formalism is used to describe the behavior of a corrugated dielectric waveguide. Explicit expressions for the dispersion near the Bragg regime are given. These are compared with the results of an “exact” analysis.     

A new approach for analysis of closed dielectric waveguides

The dispersion characteristics of a class of closed dielectric waveguides are investigated by the method which combines the building-block approach of mul timode network theory with rigorous mode matching procedure. Several numerical examples for different guiding structures have been given by the approach. The same structures are also analyzed with the finite element method and the EDC method for comparison. The calculations show that the present approach yields as highly accurate results as the finite element method while almost retaining the simplicity of the EDC method, and justify the utility of the present method     

FDTD analysis of point-defected periodical dielectric waveguides

In this paper, we utilize the finite-difference time-domain method to analyze the transmission characteristics of the point-defected periodical dielectric waveguides (point-defected PDWGs). Each point-defected PDWG contains a defected cylinder distinct from the others. It is found that the optical transmittance becomes worse due to the shorter defected cylinder but it is not affected by the longer one. Moreover, the optical transmission is very sensitive to the radius of the defected cylinder whatever it is larger or smaller than that of the other cylinders.     

Optical characteristic analysis of ridge dielectric waveguides

The optical characteristics of the ridge weak absorptive dielectric waveguide are analysed by using both the equivalent index method and the differentiation method. The approximate expressions are derived for calculating the mode loss coefficients. The computations are carried out for SiO₂/GaAs/AlGaAs waveguides. It is shown that the method given in this paper is very accurate, and the results computed by this method are in good agreement with the numerical results of the mode complex eigenvalue equations.     

Experimental analysis of metal coated dielectric waveguides

This paper concerns the experimental characteristics of metal coated dielectric waveguides with a rectangular surface corrugation. Waveguide are designed to operate at a second Bragg frequency of 90 GHz. The period, height and the duty cycle of a rectangular grating were calculated using the chosen frequency. A metallic layer of aluminum is sputtered on one side of the slab waveguide. The purpose of the metallic layer is to simulate a layer of high density plasma on the surface of the waveguide similar to that obtained by optical excitation of semiconductor structures. Experiments were performed to examine the far field radiation pattern, attenuation constant and the dispersion relation. Due to the presence of the plasma layer there will be an angular shift in the far field radiation pattern. We have observed angular shifts of about 20 in the radiation pattern of the waveguide before and after coating. Measurements are made in the frequency range of 88–95 GHz. This waveguide structure can be used to design an electronically steerable antenna and an electronic phase shifter operating in the millimeter-wave frequency band.Supported in part by the Army Research Office.     

Leaky mode analysis of circular optical waveguides

A leaky mode is a bound mode below its cut-off frequency. It attenuates in the direction of propagation and approximates the portion of the radiation field within the optical waveguide that is significant far from the source. The characteristics, including attenuation coefficients, of leaky modes on the circular fibre are compared with those of the more familiar slab waveguide. Except for the HE_1m leaky modes, leaky modes attenuate much faster on the slab than on the circular fibre. The greater the /(azimuthal field variation) the smaller the attenuatioN. Thus, theI?1 leaky modes are important even at great distances from the source. An effective cut-off frequency is proposed. Above this frequency the mode is either weakly leaky or trapped. An expression for the number of weakly leaky and trapped modes is given. The power of leaky modes due to illuminating one end of the fibre is determined. The effect of material absorption is considered.     

Numerical analysis of dispersion characteristics of flat dielectric waveguides

A method is proposed for calculation of the dispersion characteristics of flat gradient dielectric waveguides. The method is based on numerical integration of a system of ordinary differential equations obtained by differentiation of solutions of the initial boundary-value problem with respect to a parameter.Samara State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 36, No. 2, pp. 143–147, February, 1993.     

Analysis of open dielectric waveguides using the finite-element penalty method

This paper analyzes open dielectric waveguides using the vector finite-element method and boundary integral equations derived from the second Green's theorem. This finite-element formulation, together with the boundary operator, is solved using a penalty function method. Comparison with previously published results shows good agreement for the analysis of the rectangular dielectric waveguide.     

Characteristics analysis of metal-clad and absorptive dielectric waveguides by a simple and accurate perturbation method

We present a simple and accurate method for characteristic analysis of metal-clad dielectric waveguides and absorptive waveguides. The real partN of the complex modal indexN=N + iN is obtained by solving the corresponding real eigenvalue equation, and the imaginary partN is given by (n/), where= + i is the complex dielectric constant of the absorptive layer, and N/ is obtained by numerical differentiation. The method is straightforward, and the cumbersome solution of complex transcendental equations is completely eliminated. Results for simple structures are in good agreement with those obtained by exact analysis.     

二维光子晶体波导与单模平面介质波导间的喇叭波导接头

提出并优化了用于二维介质柱光子晶体波导与单模平面介质波导对接的基于分布布拉格反射波导的喇叭波导接头，提高了这两种波导之间的传输效率.二维时域有限差分仿真结果表明，在大部分光子晶体波导导模的频谱范围内，传输效率高于98％.传输效率最高可以达到99.85％. 关键词： 光子晶体波导 平面介质波导 时域有限差分     

Approximate analysis of mode dispersion in diffused-channel waveguides

We propose an approximate mode analysis using the effective index method for calculating mode dispersion in diffused channel waveguides. The method uses the minimum computing time and gives good agreement with other published results.     

Vectorial wave-matching mode analysis of integrated optical waveguides

For mode fields of integrated optical waveguides with piecewise constant and rectangular permittivity profile, Maxwell's equations reduce to the two-dimensional Helmholtz wave equation, supplemented by continuity requirements on the boundaries between different media. Two basic components of the mode field are expanded into factorizing harmonic or exponential functions, separately on each rectangular region. We determine approximations for guided modes and propagation constants by means of a minimization procedure based on a least squares expression for the mismatch in the continuity requirements. Results for the hybrid mode fields of typical sample waveguides classify this approach as competitive with and superior to alternative methods for vectorial mode analysis, although some open questions remain.     

涂覆石墨烯的非对称并行电介质纳米线波导的模式特性分析

采用多级展开方法,对涂覆石墨烯的非对称并行电介质纳米线波导的模式特性进行了分析.首先对这种波导中的表面等离子模式进行分类,然后对七种低阶模式的有效折射率和传播长度随工作频率、几何结构参数和石墨烯费米能的依赖关系进行详细的分析.结果表明,通过改变工作频率、几何结构参数和石墨烯的费米能,可以在较大范围内调节模式的特性.与有限元法进行的对比表明,基于多级方法的半解析结果与有限元法的数值结果非常符合.研究结果可为涂覆石墨烯的非对称并行电介质纳米线的设计和制作提供一定的理论基础.     

Simple approximation formulae for elliptical dielectric waveguides

A simple method to obtain accurate explicit approximation formulae for the properties of an elliptical dielectric waveguide is explained. As examples, expressions for the propagation constant, geometric birefringence, and generalized two-dimensional Petermann spot-size are derived for step refractive index profiles.     

Scalar analysis of arbitrarily shaped optical waveguides by full guided mode expansion method and optimized sine method

This paper shows that the full guided mode expansion method and the optimized sine method, with a rather rigorous procedure of determing the dimensions of reference waveguides, provide simple, fast and accurate way for the scalar analysis of arbitrarily shaped optical waveguides. Use of a smaller matrix results in good agreement with previous works.     

Low-loss, compact waveguiding with TE mode in metal/dielectric waveguides for planar lightwave circuit

We propose a low-loss metal/dielectric waveguide for compact planar lightwave circuit. The basic waveguide structure is a metal-defined high-index-contrast strip waveguide based on silicon/silica. As the guide is designed for TE single mode waveguiding, extremely low propagation loss (e.g. <0.04 dB/cm), very low bend loss (e.g. 0.0043 dB/90°-turn) and small waveguide pitch of zero-crosstalk are theoretically achievable, and can be further improved by compromising with component size and density. Examples of multi-bends and device integration are demonstrated with numerical simulations. The proposal is compatible with silicon technology and appealing for development of silicon-based planar lightwave circuit.     

The bidirectional mode expansion method for two-dimensional waveguides: the TM case

The mode expansion propagation method is a modelling technique for a large variety of waveguide components. Until now only the case with TE modes has been reported; we give details on the mode expansion propagation method for TM modes. Instead of one type of overlap integral in the TE case, a TM analysis requires two kinds of overlap integrals. The inclusion of radiation modes in this method is discussed. The modifications in the algorithm to include waveguides with gain or loss structures are also considered.As an example, the method was used for analysing a grating-assisted codirectional coupler. In particular, the radiation loss is calculated and compared with calculations when TE modes, instead of TM modes, propagate through the codirectional coupler. The radiation losses are found to be much higher for TM modes.     

Full-vectorial mode solver for anisotropic optical waveguides using multidomain spectral collocation method

A full-vectorial mode solver in terms of the transverse magnetic field components for optical waveguides with transverse anisotropy is described by using the multidomain spectral collocation method based on Chebyshev polynomials. The waveguide cross section surrounded by the perfectly matched layers is divided into suitable number of homogeneous rectangles, and then connected with by imposing the continuities of the longitudinal field components at the dielectric interfaces shared by the adjacent rectangles, resulting in a generalized matrix eigenvalue problem. To validate the established method, results of an anisotropic square waveguide and a magnetooptic rib waveguide are presented and compared with those from the full-vectorial finite difference method, full-vectorial beam propagation method, and the experimental data.