Multilayer Waveguide Structure Research Articles

Calculations of nonlinear waves in multilayer waveguides applied to polyalkylthiophenes, including linear and two-photon absorption

The TE waves in a weakly nonlinear multilayer waveguide structure are studied theoretically; linear and two-photon absorption are included in the analysis. The nonlinear material is taken to be a polyalkylthiophene. The Jacobian function model is extended to the complex plane to describe the electric field in an absorbing structure, and the results are compared with those of perturbation theory. Both the Jacobian model and perturbation theory are found to be applicable in this problem; the Jacobian model fails only for strong two-photon absorption. A figure of merit is defined to describe the capability of nonlinear operation in various optical components, and its behavior is studied. The need to reduce linear absorption remarkably and to avoid two-photon absorption is established.

Method of lines for the analysis of multilayered gyrotropic waveguide structures

The method of lines has been proved to be very efficient for calculating the characteristic properties of quasiplanar waveguides used in integrated microwave and millimetre wave circuits or in integrated optics. In the paper, it is shown how the method of lines can be applied to the analysis of quasiplanar waveguides with gyroelectric or gyromagnetic layers. The procedure described is very general. All directions of magnetisation parallel to one of the axes are taken into account. >

A boundary element technique applied to the analysis of waveguides with periodic surface corrugations

A boundary integral formulation is used to characterize Floquet-Bloch modes of two-dimensional multilayered periodic waveguides. A technique for matching fields inside the grating to those external to the grating region is described. Although a simple four-layer structure is used to illustrate the method, an extension to multilayer waveguide structures is straightforward. The mathematical formalism has been simplified, allowing for more efficient computations using fast Fourier transform algorithms. >

Cherenkov second-harmonic generation in multilayer waveguide structures

A model is presented that calculates the features of Cerenkov second-harmonic generation (SHG) in planar dielectric waveguides with an arbitrary index profile. These waveguides are represented by a stack of homogeneous layers of biaxially birefringent media. The model describes type I SHG in channel waveguides within a few approximations, such as the assumption of a quasi-slab channel geometry. Furthermore, this study comprises results of previous step-index models given in the literature, as a particular case of a one-layer structure. These results are in close agreement with measurements of the SHG efficiency in Rb-exchanged erfc waveguides in KTP materials, and in proton-exchanged step waveguides in LiNbO/sub 3/ as functions of the pump wavelength. >

Optical bistability in an excited nonlinear corrugated waveguide

An analysis is made of anomalous reflection of light from the surface of a corrugated waveguide when the refractive index of the waveguide layer depends on the radiation power. It is shown that bistable reflection of light is possible if the deviation from the optimal excitation of the waveguide is selected suitably. Estimates are obtained of the power required for bistable operation in multilayer waveguide structures composed partly of GaAs–AlGaAs superlattices.

Planar and strip optical waveguides utilizing GaAs epitaxial films and GaAs1 –xPxsolid solutions

Base multilayer epitaxial waveguide structures made of GaAs and GaAs1 – xPx solid solutions were developed and investigated. They should be suitable for integrated optical systems utilizing strip optical waveguides. An investigation and optimization of the parameters of strip waveguides made of these structures was carried out. Strip waveguides with a practically homogeneous refractive index of the base planar waveguide and almost vertical side walls of the guiding strip are fabricated. At the wavelength of 1.3 μm the losses in such waveguides were less than 1 dB/cm. An analytic expression was obtained for the effective format of a strip optical waveguide and a study was made of the influence of the parameters of a base planar or strip waveguide on its effective format for the fundamental mode.

Experimental observation of waveguide diffraction of light by Sezawa surface acoustic waves

An acoustooptic interaction was investigated in a film waveguide made of zinc oxide deposited on a thermally oxidized silicon substrate. Diffraction of laser radiation by Sezawa surface acoustic waves in the resultant multilayer waveguide structure was much stronger than that by quasi-Rayleigh waves. The acoustic and optical parameters of the structure were determined, including the acoustooptic coupling coefficients.

Non-linear waves in a multilayer waveguide: application to SiO x N y with organic overlayer

The field distribution and propagation constant are solved for a multilayer waveguide structure including a non-linear layer. Jacobian elliptic functions are found suitable as the non-linear solutions, because they lead to a numerical solution for a large variety of parameters, covering the range of non-linearity from zero to about the largest values found in any material. SiOxNy was chosen for the waveguide material and the organic conjugated polymers and liquid crystal MBBA for the overlayer. The effect of various waveguide parameters is studied and the potential applications are discussed.

Unified approach for calculating the number of confined modes in multilayered waveguiding structures

A general formalism is developed in order to find the number of modes and mode cutoff conditions in multilayer waveguiding structures. An explicit expression is presented for the number of confined modes that allows the modes to be counted without having to analyze the specific eigenvalue equation of the structure. The method is illustrated by its application to several structures: the buried layer, the directional coupler, and the three-guide symmetrical arrangement. By a suitable extension of the formalism, the number of well-confined modes is found for a four-layer structure.

Investigation of grating structures in composite waveguides

An investigation was made of mode matching in multilayer waveguide structures using inclined volume phase grating structures and methods of recording these were compared. An analysis was made of the feasibility of using these structures to match waveguides having different refractive indices on a single substrate. A study was made of the influence of the interface between the waveguides on their matching efficiency. A matching efficiency of ~80% was achieved.

Multilayer gyrotropic waveguide structures with azimuthal magnetization

An algorithm to obtain the dispersion equation and to determine the field configuration in the case of an arbitrary number of layers is developed by the successive joining of tangential components of the eigenwave electromagnetic field of a regular waveguide with concentric azimuthally magnetized gyrotropic layers. The electrical and magnetic field components in each layer are represented in the form of a linear combination of four particular analytic solutions of the system of generalized wave equations. By using an electronic computer the phase and dissipation characteristics of circular and coaxial waveguides with azimuthally magnetized ferrite-dielectric layers are computed for variations in their material and geometric parameters.

Improved coupled mode analysis of corrugated waveguides and lasers

Corrugated waveguides and lasers in resonant and non-resonant situations are analyzed by an improved coupled mode theory based on a set of the coupled mode equations for guided modes and radiation continuum. The distributed feedback (DFB) coefficient and the radiation loss coefficient are given in closed forms. The formulation can be applicable to arbitrarily shaped gratings and multilayer waveguide structures. The accuracy of the theory is examined by comparing it with Tamir's exact calculation for a nonresonant situation and also with Streifer's one for a DFB structure. Reasonable accuracy is obtained by the proper choice of the unperturbed waveguide parameter. The dependence of the two coefficients on the grating depth, the grating period, the guide layer thickness, and the refractive index difference between core and cladding layers is obtained for all Bragg orders up to the fourth, and for four typical grating shapes, namely, for rectangular, sinusoidal, symmetric triangular, and sawtooth gratings. Both the threshold gain of DFB lasers utilizing higher order Bragg reflection and the output coupling efficiency of grating beam couplers are also calculated for these parameters. A new multilayer structure for controlling the radiation loss is proposed and analyzed. This structure is suitable for the suppression of the radiation loss in DBR reflectors as well as for the improvement of the output coupling efficiency in grating beam couplers.