Numerical modeling of multimode doped optical waveguides

Abstract

In recent years, several papers have addressed the modeling of wave propagation through doped optical fibers and micrometer waveguides. These devices exhibit gain and are essential for optical processing applications. Recently, an efficient self-consistent numerical scheme for modeling short doped optical waveguides was published in the literature. Given an input pump and signal beams, a set of three-level rate equations are solved for modeling the interaction between the optical waves and the active doped media. This result is used to compute the permittivity profile accurately, which in turn is used to compute, by means of a finite element code, the associated modes for the pump and signal beams. Next, these updated beams are used in the solution of the rate equations and so on, until a self-consistent convergence is reached. However, this scheme only takes into account monomode waveguides. On the other contrary, in order to obtain higher gain levels, highly confined modes might need to be launched—the pump in particular—and consequently, higher order modes may be excited. In this work we extend the self-consistent scheme for multimode waveguides, therefore, substantially enlarging its range of practical applications. Comparisons with other numerical schemes and experimental results, confirm the efficiency and accuracy of our model.