Propagation characteristics of nonlinear graded-index optical waveguides

We describe a quite general and accurate approach for determining the dispersion equation of TE-polarized modes propagating in planar graded-index waveguides bounded on one side by a self-focusing nonlinear cover with finite thickness. The proposed structure appears to be appropriate for wavelength converters based on a four-wave mixing process. The dependence of the guided power flow along the proposed four-layered structure (which is different from others previously published) on the refractive-index profile parameters is investigated. The validity of the reported numerical results is confirmed by the beam-propagation-method simulation. Moreover, a particular waveguide configuration is described, one especially designed to maximize the power confinement in the nonlinear medium.