Stability of solitons in nonlinear fiber couplers with two orthogonal polarizations

Abstract

In T. Lakoba, D. Kaup, and B. Malomed [Phys. Rev. E 55, 6107 (1997)], the stationary solitons of the nonlinear directional coupler (NLDC) with two polarizations in each core were studied and detailed by means of the variational method. In the present work, we show how one can analytically determine the stability of all the various solitons found in that previous work in the limit of large soliton energy. We emphasize that our analysis is not based on the variational approximations for the solitons, but rather on their asymptotically exact forms in the limit of large energy. We find that in all but one case, the stability of those solitons in this model, which are analogs of any soliton of the NLDC, is the same as that of the corresponding NLDC soliton. We also discuss how our results, valid for large soliton energies, can be extended to finite values of energy.