Carlos R. Paiva

All-optical pulse switching in twin-core fiber couplers with intermodal dispersion

Due to the dispersion mismatch between the two supermodes of a two-channel coupler, pulse switching cannot be analyzed without taking into account the effect of intermodal dispersion. Using full numerical simulations, we show the influence of intermodal dispersion on all-optical switching with ultrashort pulses in twin-core fiber couplers. For the nonlinear regime, however, only subpicosecond and femtosecond pulses are affected in the cross state since the parallel state remains almost unaffected.

A linear-operator formalism for the analysis of inhomogeneous biisotropic 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. >

Full-wave analysis of a nonradiative dielectric waveguide with a pseudochiral /spl Omega/-slab

This paper presents a new microwave device - a non-radiative dielectric (NRD) waveguide with a dielectric pseudochiral /spl Omega/-slab - the /spl Omega/-NRD waveguide. A rigorous full-wave analysis is presented and the modal equations for the longitudinal-section magnetic (LSM) and longitudinal-section electric (LSE) modes are derived. The dispersion curves and operational diagrams for the first hybrid LSM modes are presented. The effect of the pseudochiral /spl Omega/-medium is discussed. New interesting modal features are revealed, showing that the propagation characteristics may differ considerably from the common isotropic case.

Anisotropy without tensors: a novel approach using geometric algebra

The most widespread approach to anisotropic media is dyadic analysis. However, to get a geometrical picture of a dielectric tensor, one has to resort to a coordinate system for a matrix form in order to obtain, for example, the index-ellipsoid, thereby obnubilating the deeper coordinate-free meaning of anisotropy itself. To overcome these shortcomings we present a novel approach to anisotropy: using geometric algebra we introduce a direct geometrical interpretation without the intervention of any coordinate system. By applying this new approach to biaxial crystals we show the effectiveness and insight that geometric algebra can bring to the optics of anisotropic media.

Dispersion and Losses in Surface Waveguides Containing Double Negative or Chiral Metamaterials

In this article the in∞uence of both dispersion and losses on waveguides with metamaterials is investigated. The analysis is focused on surface waveguides (planar interfaces and grounded slabs) containing either double-negative (DNG) or chiral metamaterials. The main goal is to show how the combined efiect of material dispersion and losses with the structural dispersion afiect the solutions of the modal equations. It is shown that this interplay is essential to obtain a correct modal analysis of these waveguides. Namely, the overall behavior can qualitatively change | so that it is not possible to state that the corresponding lossy case | even when a very small amount of losses is introduced | can be interpreted as a small perturbation of the lossless case.

Modified split-step Fourier method for the numerical simulation of soliton amplification in erbium-doped fibers with forward-propagating noise

Using a modified version of the split-step Fourier method, we analyze the effect of noise on soliton propagation inside erbium-doped fiber amplifiers. In fact, noise from forward-propagating amplified spontaneous emission, associated with a Markov immigration process, is included in the analysis of soliton amplification. Moreover, this algorithm accounts for the real spectral gain profile of the fiber amplifier. The frequency jitter, induced during soliton amplification, is compared with the Gordon-Haus effect where optical amplifiers are considered as noisy point-like devices.

Effect of Losses in a Layered Structure Containing DPS and DNG Media

The problem of re∞ection and transmission of plane electromagnetic waves in a periodic multilayered structure containing double-negative (DNG) media is analyzed using a matrix formalism. A Lorentz model with a single resonance is used to describe the dispersion of the DNG medium. It is shown that the introduction of losses, in accordance with the Kramers- Kronig relations, is essential in order to obtain correct results on the performance of the structure.

ELECTROMAGNETIC WAVE PROPAGATION IN CHIRAL H-GUIDES

Guided-wave propagation in chiral H-guides is analyzed, using a building-block approach. In a flrst stage, a 2D chiral parallel-plate waveguide is studied using a lossless frequency dispersion model for the optically active medium, where the constitutive chiral parameter is assumed to be dependent on the gyrotropic parameter. In the second stage, the mode matching technique and the transverse resonance method are used to characterize the 3D structure. A full parametric study is presented for a flxed frequency. The operational and dispersion diagrams for the chiral H-guide are presented. By replacing the common isotropic slab with a chiral slab, chirality provides an extra degree of freedom in the design of new devices.

Semileaky waves in dielectric chirowaveguides.

The occurrence of semileaky waves in dielectric chirowaveguides is investigated. It is shown that a thinfilm dielectric chiroslabguide with an achiral superstrate and in which both the film and substrate are chiral can support semileaky modes radiating energy into the substrate, provided that the chirality parameters are properly chosen.

Doppler Shift from a Composition of Boosts with Thomas Rotation: a Spacetime Algebra Approach

As is well-known, Lorentz boosts do not form a group: the composite of two boosts is, in general, equivalent to the composite of a rotation — the so-called Thomas (or Wigner) rotation — and a single boost. Using spacetime algebra, the geometric algebra for Minkowski spacetime, we show in this paper how to relate the Thomas rotation to the Doppler shift experienced between two observers in relative motion. Both observers are moving away from a third observer, set in the laboratory, with relative non-parallel velocities.