Pulse propagation in a nonlinear dielectric slab waveguide

The evolution of an optical pulse in a single-mode, step index dielectric slab waveguide which is characterized by an intensity dependent dielectric function in the core and cladding regions is treated by means of differential equation techniques. A cubic order non-linearity is considered. The electromagnetic field distribution in the slab waveguide region satisfies a non-linear wave equation. This field can be represented in terms of even TE guided modes with a slowly varying envelope amplitude function. Then using the well known approximation, based on the slowly varying character of the amplitude function, a non linear partial differential equation is obtained for the amplitude function. As the coefficients of this equation depend on the distance across the transverse direction X, an averaging technique over x is applied to reduce the nonlinear partial differential equation into a form that is easily transformed to the so-called non-linear Scroedinger differential equation. This equation is then attacked by means of the well known Inverse Scattering method in the case of reflection less potentials. The single and double soliton solutions are obtained explicitly for a single-mode slab waveguide. Finally numerical results are presented in the time domain.     

Approximate solution for step discontinuity in dielectric slab waveguide

A simple method is presented for obtaining approximate expressions for the power reflection and transmission coefficients of surface waves scattered by a step discontinuity in a dielectric slab waveguide. The approximation is compared with Rozzi's exact solution. Agreement is quite good for a wide range of the relevant parameters.     

A novel wide-angle low-loss dielectric slab waveguide Y-branch

A new Y-branch structure for dielectric waveguides is proposed and analysed using simple geometrical optics and beam propagation methods. It is shown both qualitatively and quantitatively that the proposed structure has larger branching angles but lower radiation loss than those associated with either conventional Y-branches or structures with antenna coupled and phase front accelerators. The optimal design parameters calculated by numerical simulations are in very good agreement with those found from the geometrical optics. The simulations also reveal that the performance is fairly insensitive to fabrication errors     

Rigorous asymptotic analysis of transmission through a curved dielectric slab

A circular cylindrical dielectric layer is an idealized but rigorously analyzable model for radome covers. With a line source located on the concave side, an exact integral formulation is derived for the field transmitted to the convex side. Alternative representations are developed therefrom in terms of discrete guided modes and continuous spectra, and of ray integrals which, asymptotically at high frequencies, yield geometric optical fields that experience multiple internal reflections between the layer boundaries and also multiple reflections on the concave side. It is then shown that the higher order multiple reflected contributions can be expressed collectively as a ray field with a weighted transmission coefficient that is equivalent to the plane wave transmission coefficient for a plane parallel layer but includes a simple curvature correction. When source and observer are close to the inner and outer layer boundaries, respectively, and are also separated by a large angular interval, guided mode effects may have to be included as well. The result is a general and novel representation of the transmitted field in terms of a certain number of ordinary multiple reflected geometric optical ray fields, a single "collective" ray field, which includes in a composite manner all of the remaining internal reflections, and, possibly, the guided modes along the layer.     

Design of slot arrays in waveguide partially filled with dielectric slab

The Elliot procedure for the design of a waveguide slot array is extended to the case of partially filled radiating waveguides. The dielectric slab lies on the top of the radiating waveguide, i.e. on the slotted wall. The proposed solution prevents some of the most common drawbacks of waveguide slot arrays. Results are validated against a commercial FEM software.     

Reflection of millimeter waves by a corrugated dielectric slab waveguide

The TM wave propagation in a corrugated dielectric slab has been studied using a singular boundary perturbation procedure, which is supported subsequently by experiments in the millimeter-wave region.     

New rigorous analysis of the step discontinuity in a slab dielectric waveguide

The scattering of the even TE guided modes incident on a step discontinuity in a planner dielectric waveguide is analysed by means of a novel integral formulation. An accurate numerical solution is obtained from an iterative procedure needing a successive order of approximation in the scattering mechanism.     

New dielectric waveguide structure for millimetre-wave optical control

A new dielectric waveguide structure is presented for obtaining large attenuation for millimetre-wave optical control. It is found that the attenuation of the proposed structure is an order of magnitude larger than that of a commonly used rectangular semiconductor waveguide.     

梯形截面介质光波导的模方程

本文简化了有效折射率法和WKB法对梯形截面介质光波导传输特性的分析过程,给出了计算E_(mn)~X模有效折射率的近似模方程,并用数值计算结果和实验结果检验了该模方程的精度。     

Semiempirical relation for curved optical waveguide design in theedge-guided mode regime

A semiempirical relation has been developed for determining the minimum allowable radius of curvature of a circular waveguide with an edge-guided fundamental mode. The specified parameters are the wavelength, the effective refractive index of the waveguide, the lateral index step, and the allowable radiation loss coefficient. This relation was fitted and verified against numerically evaluated solutions of Maxwell's equations in two dimensions for lateral index steps 0.01<ΔN<0.1, for effective indices of refraction 3xGa_1-xAs system), and for radiation losses of 10^-4 <α_r<100 cm^-1. The difference between the results of solving Maxwell's equations and the semiempirical relation over these parameter ranges was determined to be less than 2%     

Nonlinear TE waves in a dielectric slab waveguide with two optically nonlinear layers

Properties of TE waves in a slab waveguide composed of five layers, including two Kerr-like nonlinear layers, are analyzed and examined. We find in particular the occurrence of an asymmetric mode, in addition to the expected symmetric and antisymmetric modes, though the waveguide geometry is symmetric. For the TE0symmetric mode, TE1antisymmetric and asymmetric modes, the dispersion curves, the relations between the effective index and the optical power density, and the variations of the transverse electric field patterns are illustrated and discussed in detail. As a result of this analysis, the regions in which the respective modes mainly reside are elucidated. We find that the effective index value of the symmetric mode at which the guide power vanishes is larger than that of the antisymmetric mode. For the case in which the effective indexes of the asymmetric and antisymmetric modes are identical, the power in the former mode is found to be larger than that in the latter.     

基于纳米多孔薄膜的对称平面光波导湿度传感器

通过在对称平面玻璃光波导上下表面各制备一层纳米多孔TiO2薄膜,形成了一种简单新颖的光学湿度传感器。其原理为,导波光在平面对称光波导中的传播损失依赖于纳米多孔Ti02薄膜的平均折射率,后者依赖于薄膜内部的水分子吸附量,而薄膜的水分子吸附量随着周围相对湿度的变化而变化,通过实时测量导波光传播损失的变化就能够感知外围的相对...     

Scattering and mode conversion by a screen-like inhomogeneityinside a dielectric slab waveguide

In this paper, the interaction of surface guided waves with a perfectly conducting scatterer shaped as a part of a circular screen and placed into a dielectric slab waveguide is investigated in mathematically correct manner. Due to the geometry of screen the original boundary value problem is reduced to dual series equations treated further by means of the Riemann-Hilbert Problem technique. Based on this approach, the numerical solution can be obtained, theoretically, with any desired accuracy. The reflection, transmission, and radiated-field quantities are computed for both single-mode and multimode slab guides containing cavity-shaped and strip-shaped scatterers     

Vector analysis of optical dielectric waveguide bends usingfinite-difference method

A full-vectorial analysis of optical dielectric waveguide bends using the finite-difference method has been developed. The formulation was based on the transverse electric field components, E_r and E_z. To set up the boundary conditions at each dielectric interface, the continuity of E_&thetas;, H_&thetas;, and the tangential component of the electric field, and the discontinuity of the normal component of the electric field were satisfied. The finite-difference scheme was modified to satisfy these boundary conditions. The results of the analysis using the current method is compared with previous results. The optimal offset for 90° bends was obtained, and the losses for these optimal bend structures are also presented     

Theory of an ultra-broad-band optical dielectric waveguide coupler system

A technique is described for operating a prism to dielectric thin-film waveguide system over a wide frequency band from a conventional broad-band source of the dye-laser type. The continuous coupling bandwidth can extend, typically, over a frequency range of twice to three times the center frequency. The experimental tolerances have been established and are shown to be within the capability of present-day technology.     

Analysis of propagation characteristics of whispering gallery modes in a dielectric disk or a curved rectangular dielectric waveguide

The finite-element method is applied to the analysis of whispering gallery modes in curved optical waveguides. Numerical examples for whispering gallery modes in a dielectric disk with rough boundaries are given. It is demonstrated that the whispering gallery modes and the normal guided modes in a curved rectangular dielectric waveguide are analyzed consistently with this approach, and that the normal guided mode approaches the whispering gallery mode with the increase of waveguide width. The minimum width of the rectangular waveguide needed to support a whispering gallery mode is evaluated.<>     

Birefringence in curved single-mode optical fibers due to waveguide geometry effect--Perturbation analysis

The field deformation in curved step-index single-mode circular fibers and the birefringence induced by the curved waveguide geometry are analyzed by a perturbation method. We find that the values of the birefringence are proportional toa^{2}/R_{0}^{2}and are much less than those induced by stress. A square optical waveguide is also investigated. We find birefringence values of roughly the same order of magnitude as those for the circular waveguide.     

Finite-element analysis of the discontinuities in a dielectric slab waveguide bounded by parallel plates

A method for the solution of the discontinuity problem of TE modes and TM modes in a dielectric slab waveguide bounded by parallel plates is described. The approach is a combination of the finite-element and the analytical method. Results are compared with those given by previous authors.     

Fast and accurate analysis of 3-D curved optical waveguide couplers

The structure-related (SR) finite-difference beam-propagation method is applied to integrated optical couplers employing curved waveguide sections. A general nonorthogonal coordinate system is introduced that matches the local structure geometry, yielding a more accurate analysis with coarser meshes than standard schemes, thus providing significant computational resource savings. Furthermore, the algorithm is easily interfaced with conventional schemes. Examples of curved two-dimensional and three-dimensional directional waveguide couplers are examined to show the advantages and generality of SR schemes as well as to explore the role of the extra degrees of freedom offered by nonorthogonal meshing.     

Rigorous TE solution to the dielectric wedge antenna fed by a slab waveguide

A rigorous TE solution to the dielectric wedge antenna fed by a slab waveguide of the same material is presented. The method of solution involves modeling the wedge as a sequence of step discontinuities and uses an iterative procedure to track forward and backward partial wave fields, expressed as modal expansions, to obtain the rigorous field solution. Radiation patterns of directive gain are presented. All patterns smoothly decrease from a maximum in the endfire direction and exhibit extremely low side lobe levels. Longer length wedges or smaller dielectric constant materials are shown to produce higher directivity and smaller half-power beamwidths. For slender, gradually tapered wedges, the reflection coefficient of the guided (surface) wave at the input to the wedge is very small indicating a low VSWR for tapered dielectric antennas and there appears to be no gain limitation with antenna length for these antennas.