VARIATIONAL APPROXIMATIONS AND MODE-STABILITY IN PLANAR NONLINEAR WAVE-GUIDES

In a previously published paper we used a variational method with simple trial functions to find accurate approximations for the modes of waveguides in which the nonlinearity is confined mainly to the core. Systems in which the nonlinearity occurs in the cladding present more difficulties because the solution at a particular power may not be unique. There may be two, or more, nonlinear modes with quite different intensity profiles and stability properties corresponding to the one linear mode. We apply our variational method to planar waveguides with this more general distribution of nonlinear material and also investigate the relationship between the stationary properties of our solutions and modal stability.