Paul Lagasse

Beam-propagation method: analysis and assessment

A method for the calculation of the propagation of a light beam through an inhomogeneous medium is presented. A theoretical analysis of this beam-propagation method is given, and a set of conditions necessary for the accurate application of the method is derived. The method is illustrated by the study of a number of integrated-optic structures, such as thin-film waveguides and gratings.

Calculation of radiation loss in integrated-optic tapers and Y-junctions

Mode conversion and radiation loss in integrated-optic tapers and Y-junctions are calculated by means of the beam propagation method combined with the effective refractive-index method. Simple design rules for the tapers and Y-junctions are derived from the obtained results.

Loss calculation and design of arbitrarily curved integrated-optic waveguides

Radiation losses in arbitrarily curved integrated-optic waveguides are computed numerically by means of the beam-propagation method. From the results obtained, design rules for bends and S-shaped curves connecting two straight waveguides are derived.

Integrated optic devices based on nonlinear optical polymers

An examination is made of the state of the art of nonlinear optical polymeric materials in view of their potential advantages. It is shown that these organic materials have many attractive features compared to LiNbO/sub 3/ and III-V semiconductors with regard to their use in integrated optic circuits, especially since the level of integration is ever increasing. Considering more specifically electro-optic devices, a description is given of some of the theoretical background and basic properties. These polymers have already demonstrated a very high and extremely fast electro-optic effect compared to LiNbO/sub 3/. It is also shown how low-loss waveguides can be fabricated by using easy techniques such as direct UV bleaching. The performance of phase modulators, Mach-Zehnder interferometers, and 2*2 space switches built with such polymers is already very promising. >

Acoustic surface waveguides - Analysis and assessment

The properties of acoustic surface waveguides are reviewed, with particular reference to topographic structures in which guiding is achieved by drastic deformation of the substrate surface. A numerical technique, capable of computing efficiently and with high accuracy the mode spectrum of an anisotropic piezoelectric heterogeneous waveguide of arbitrary cross section, is described. Characteristics of both the ridge guide and the recently discovered wedge waveguide are discussed in some detail. Techniques for the fabrication of and transduction onto acoustic surface waveguides are discussed, and a preliminary assessment is made of potential linear and nonlinear waveguide applications. A number of experimental devices are described.

Mixed potential integral equation technique for hybrid microstrip-slotline multilayered circuits using a mixed rectangular-triangular mesh

In this paper, a mixed potential integral equation (MPIE) formulation for hybrid microstrip-slotline multilayered circuits is presented. This integral equation is solved with the method of moments (MoM) in combination with Galerkins method. The vector-valued rooftop functions defined over a mixed rectangular-triangular mesh are used to model the electric and magnetic currents on the microstrip and slotline structures. An efficient calculation technique for the quadruple interaction integrals between two cells in the system matrix equation is presented. Two examples of hybrid microstrip-slotline circuits are discussed. The first example compares the simulation results for a microstrip-slotline transition with measured data. The second example illustrates the use of the simulation technique in the design process of a broadband slot-coupled microstrip line transition. >

Coupled wave analysis of obliquely incident waves in thin film gratings

The problem of a guided wave obliquely incident on a grating etched in a thin film guide is considered. Two-dimensional coupled wave equations for the incident and reflected beams are derived for the cases of TE-TE, TE-TM, and TM-TM coupling. Two methods, a ray optic approximation and a coupled beam method, are proposed for the numerical solution of the coupled wave equations. Both methods are illustrated by a number of calculated examples.

Longitudinal analysis of semiconductor lasers with low reflectivity facets

An analysis is made of longitudinal effects in semiconductor lasers with low facet reflectivities. For this purpose, a self-consistent model is used based on the beam propagation method, which takes into account both the lateral and longitudinal dimension. The calculations show that longitudinal effects have a significant influence on the output fields in the laser.

High‐reflectivity GaAs‐AlGaAs mirrors: Sensitivity analysis with respect to epitaxial growth parameters

High‐reflectivity multilayer structures, consisting of a periodic stack of quarter‐wavelength GaAs and AlGaAs layers, have been investigated concerning their optical behavior with respect to various deficiencies in the epitaxial growth process. Theoretical curves are compared with experimental ones from structures grown by metalorganic chemical vapor deposition. These layer structures are also shown to be useful in the characterization of thickness uniformity of an epitaxial growth process.

Application, design, and evolution of WDM in GTS's pan-European transport network

A pan-European transport network must cope with enormous traffic inflation by introducing appropriate network solutions. WDM technology is the solution adopted by GTS, driven by capacity requirements, infrastructure availability, flexibility, and cost. The deployment of this new technology presents specific technical issues, but more important, it lays the foundation of future optical networking. We describe the motives underlying the deployment of WDM technology in the long-haul and short-haul areas of GTSs operational transport network. Next, after presenting the use of WDM as the multiservice platform for SDH and IP overlay networks as well as native WDM services, we focus on the design of SDH-over-WDM and IP-over-WDM networks. Finally, we discuss future WDM networking and management requirements to better serve the needs of a pan-European carrier such as GTS.