Nonlinear polarization dynamics of counterpropagating waves in an isotropic optical fiber: Theory and experiments

The nonlinear interaction between two intense counterpropagating laser beams in an isotropic optical fiber may lead to spatiotemporal polarization instabilities of both waves. Experiments with various mutual polarization arrangements and different powers of the two counterpropagating input beams showed that nonlinear birefringence may lead to significant polarization cross switching of both beams. In the case of two counter-rotating circular input waves, the cross-polarization interaction of the beams led to the generation of a polarization kink or domain wall soliton. This soliton is formed by a superposition of counterpropagating waves that represent switching of the state of polarization of light between two domains where both waves are circularly polarized and corotating. The experimental observations are found to be in good agreement with the theoretical predictions.