Third-order nonlinear integrated device based on an effective graded-index waveguide for all-optical multistability

We present a theoretical study of all-optical multistability in an integrated device composed by a step-index nonlinear Kerr waveguide with a variable width film, providing an effective graded-index profile. The self-and cross-action of nonlinear Gaussian counterpropagating beams in this structure and a feedback controlling mechanism based on transverse modal coupling generate a multistable behavior. The results have been obtained and explained on the basis of the exact solutions of the variational problem for the counterpropagating Gaussian beams. Finally, in order to make clear the possibilities of this device, novel applications of the all-optical multistable integrated device are proposed for smart sensing.