一种多层波导光传播计算的新方法

提出了一种新的简单的一光学方法，可以使用在多层波导的光传播计算中，尤其是在光探测器的设计中。把设计值与目前普遍采用的ＢＰＭ法进行比较，结果吻合较好。与ＢＰＭ法相比，此法最大的优点是在计算中考虑了材料对传播光的吸收，而在光场达到稳定分布后再考虑吸收，故在理论上此方法更加接近实际。作为例子用这种方法计算了一种新型的探测器的尺寸。这种探测器与Ｓｉ波导的集成器件正在制作 中。     

A novel cavity resonator measurement method for leaky waveguides

The authors present a method for measuring the phase and leakage constants of leaky waveguides in which power is sent in transversely, in a reversal of the leakage process itself. The cavity therefore requires no coupling holes, and the method is accurate and convenient to use, as shown in an illustrative example     

A new equivalent network method for analyzing discontinuityproperties of open dielectric waveguides

A novel network approach is proposed for analyzing interacting discontinuities on open planar dielectric waveguides by accurately taking account of both surface modes and waves with continuous spectra. In this approach, a continuum of the radiation wave is recomposed into a set of the newly defined spectral composite modes, each of which carries a finite magnitude of radiation power. These new modes, in conjunction with surface modes, construct the complete orthonormal set for expressing an arbitrary local field on a dielectric slab waveguide. This leads to an equivalent network approach effective for solving discontinuity problems, even on an open waveguide using the conventional method for closed-waveguide problems. A number of numerical results are shown to demonstrate the usefulness of the proposed approach     

平面传输线上漏波的仿真研究

介绍了平面传输线的漏波特性,对平面传输线上由delta-gap源激励的漏波的电磁场分布进行了仿真分析,包括槽线上的二次表面漏模和空间漏模,以及双面槽线上(CBSL)的主漏模和表面漏模。场分布通过时域内的数值计算进行仿真。仿真结果给出了由delta缝隙源激励的漏波的特性,同时给出了研究漏波的一个有用的工具。     

The method of lines applied to planar transmission lines incircular and elliptical waveguides

The method of lines (MOL) is utilized to analyze a class of planar transmission lines with circular or semicircular/elliptical metallic shielding. The authors show how the general MOL principles can be modified so that curved boundary structures can be included. Dispersion diagrams are presented for microstrip and slotline structures with curved metallic shielding as well as for their suspended counterparts in circular and elliptical waveguides. Results show that some of the structures have potential applications at millimeter-wave frequencies because losses in circular waveguide enclosures are generally lower than those in rectangular waveguides     

Prism-coupling of light into narrow planar optical waveguides

The efficiency and selectivity of the prism-coupler for exciting single modes in narrow planar optical waveguides is investigated both theoretically and experimentally. A previously published calculation of the coupling efficiency between a plane input wave with finite cross section and a number of waveguide modes, as a function of both the incidence angle and the skew angle, is extended to include the effects of diffraction, which are shown to play a dominant role for small focal widths of the input beam. The theoretical predictions are compared with experimental results obtained at 633 nm on an embedded ridge-type waveguide structure. A number of mechanisms reducing coupling selectivity and stability are discussed, and some practical rules are given for obtaining good stability and selectivity     

A MATRIX METHOD FOR SOLVING PLANAR DIELECTRIC OPTICAL WAVEGUIDES

A matrix method used in multilayer stack of dielectric films is applied-to planar dielectric optical waveguides. A simple and applicable method for obtaining characteristic equation is presented.     

A variational finite-difference method for analyzing channel waveguides with arbitrary index profiles

A variational, finite-difference method for computing the normalized propagation constants and the normalized field profiles of channel waveguides with arbitrary index profiles as well as aspect ratios is presented. Mode dispersion curves and the field profiles of the fundamental mode of channel waveguides having profiles of practical interest are included.     

A refined WKB method for symmetric planar waveguides withtruncated-index profiles and graded-index profiles

An accurate method is proposed, based on a modified version of the WKB method in quantum mechanics, for evaluating the propagation constants and field distribution of symmetric planar waveguides with a truncated-index and graded-index profile. Simple formulas are given for calculating the dispersion characteristics including those for the truncated parabolic and exponential profile, and results are much more accurate than those of the ordinary WKB method, especially in the near cutoff regions. This method also can be extended to other more complicated cases     

The method of lines for the analysis of lossy planar waveguides

The method of lines is extended to calculate the losses of waveguide structures. Ohmic losses in metallizations (with frequency-dependent, extremely high dielectric constants) and dielectric losses are simultaneously considered. Despite the high ratios of the dielectric constants of the metallizations and the dielectrics, the analysis and numerical treatment are carried out accurately. Using nonequidistant discretizations the results are computed efficiently, and an approximate value of the propagation constant close to the exact value is found by extrapolation. The phase constant deviates less than 0.5%. The attenuation may deviate up to 2%. The advantages of the method of lines are a small computation time and, due to the analytical solutions of the fields in one direction, a very good approach to the fields inside the strip as well as to the strong fields directly adjacent at the edges. The results for a single microstrip line are shown and compared with those of other authors     

Fundamental properties of radiation from a leaky mode excited on a planar transmission line

By using a specific normalization, it is shown that the TM/sub 0/ radiation field from a leaky mode that is excited by a source on any printed-circuit structure can be represented in a unified manner. The general properties of the normalized leaky-mode radiation field are examined in detail for a variety of phase and attenuation constants, as well as distances from the source, and for different types of source excitations. The normalized leaky-mode radiation field is compared to similarly normalized geometrical-optics and far-field radiation expressions to provide further insight into the nature of the radiation fields in the near- and far-field regions. The results provide a general view of leaky-mode radiation properties independent of the type of planar transmission line or background structure.     

Analysis of discontinuities in planar dielectric waveguides: aneigenmode propagation method

The eigenmode propagation method is proposed to analyze the discontinuity problems in planar dielectric waveguides. This recursive algorithm is based on the numerical mode matching method, but it uses less computation time and computer memory, which makes the analysis of multiregion, vertically stratified media much more effective. With this algorithm, the required computer memory is independent of the number of regions in the problem, and the computation time is linearly proportional to the number of regions. Therefore, it is particularly suitable for the analysis of planar waveguide discontinuities and waveguide bends. Using this method, larger problems can be analyzed which are impractical with the finite element method. Numerical examples are given to demonstrate that the computation time is linearly proportional to the number of discontinuities, while the computer memory is almost a constant independent of the number of discontinuities     

Minimization of reflection error caused by absorbing boundarycondition in the FDTD simulation of planar transmission lines

Residual reflection from absorbing boundaries introduces considerable error in the frequency-domain parameters of open-region planar transmission line components simulated in the time-domain. Various dispersive and super-absorbing boundary conditions have been developed to minimize this reflection. In this paper, a computationally efficient method, termed as geometry rearrangement technique (GRT), is proposed to correct the dominant reflection from absorbing boundaries by superposition of two subproblems with different source or boundary locations. The computational improvement of GRT is demonstrated by the FDTD simulation of dispersion in microstrip and coplanar transmission lines. A new method is discussed to accurately estimate the boundary reflection, and then applied to correct the characteristic impedance of planar transmission lines for boundary reflection     

A new method for analyzing the security of cryptographic protocols

A formal method for analyzing the security of cryptographic protocols is presented. This method is based on an original representation of the participants' knowledge. The author proves the probabilistic properties of the cryptographic protocols and models the possible attacks on these protocols. This method is applied to well-known protocols like the Kerberos authentication protocol and the X.509 standard     

The new method of time-domain analysis of a planar transmission line with discontinuity

In this paper, the new technique of time-domain analysis of discontinuities in a planar transmission line is presented. In the process of time-domain analysis, the analysis model of system and the concept of transfer function are employed and the frequency-domain method of lines and the technique of the fast Fourier transform are used. The results of time-domain data and frequency-domain characteristics for the shielded microstrip with step discontinuity are given and compared with the published results of other authors.     

Multiple scattering among vias in lossy planar waveguides using SMCG method

Large-scale full-wave multiple scattering among cylindrical vias in planar waveguides is modeled using the Foldy-Lax equation. The formulation includes the skin effects of the conducting power/ground plane. Numerical solution of the Foldy-Lax equation with large number of unknowns is computed efficiently using the sparse-matrix canonical-grid method. In this method, interactions among vias are decomposed into the strong interactions part and the weak interactions part. The calculation of the weak part is carried out using two-dimensional (2-D)-fast Fourier transform (FFT) by translating the locations of the vias onto the uniform grids. The final solution of the Foldy-Lax equations is calculated by an iterative method. The results show O (N log N) CPU efficiency and O (N) memory efficiency. This makes large scale via problems possible for computer simulation.     

A Planar transversal junction of two planar waveguides

A rigorous analytic method is used to solve the wave-propagation problem for a planar transversal junction of two planar waveguides. The problem is reduced to an iteratively solved system of integral equations of the second kind. Dependences of the transmission and reflection coefficients of guided waves, radiation patterns, and the power of the radiation field on the ratios of the waveguide thicknesses and the waveguide permittivities are obtained.     

A new method for producing graded index PMMA waveguides

We report a new method for producing graded index polymethyl methacrylate (PMMA) waveguides using optical densification by angled X-ray exposure. The resulting larger refractive index near the surface of the waveguide serves to better isolate the guided light from potentially absorbing or scattering substrates than in waveguides of constant refractive index. We calculate that a 65° angle exposure in 6-μm-thick planar PMMA waveguide shifts the peak of the fundamental mode profile ~0.5 μm away from the substrate. Consistent with this result, we measure a reduction in the propagation loss of PMMA planar waveguides on a Ni substrate from 1.5 dB/cm to 0.5 dB/cm after angle X-ray exposure     

A linear-operator formalism for the analysis of inhomogeneousbiisotropic planar waveguides

Using the theory of linear operators, guided electromagnetic wave propagation in inhomogeneous (nonreciprocal) biisotropic planar structures is analyzed in terms of a 2×2 matrix differential operator. Based on the concept of adjoint waveguide, a new biorthogonality relation for the guided hybrid modes is derived. For the special case of reciprocal biisotropic media or chiral media, the linear-operator formalism leads to a self-adjoint problem. As an application example, a general analysis of the radiation modes of a grounded chiroslabguide is also presented     

Bent planar waveguides and whispering gallery modes: a new methodof analysis

A matrix method for analyzing bent planar optical waveguides is discussed. The method is a modification of an earlier method which yields bend loss directly, inasmuch as a nonuniform refractive index is approximated by a series of linear profiles rather than a series of uniform profiles. The method can be used with absorbing or leaky structures. The effect of whispering gallery modes has also been studied. It appears that a whispering gallery explanation given by H.J. Harris and P.F. Castle (1986) may not be adequate