Dark solitons in weakly saturable nonlinear media

Exact explicit analytical solutions of dark (gray and black) solitons to the quintic nonlinear Schrodinger equation that includes the first high order nonlinear saturable term are presented. The dark solitons in the weakly saturable self-defocusing media are shown to be stable to a small perturbation (noncollision type) and, as in the case of a Kerr nonlinearity, the two black solitons launched in parallel repel with propagation distance. However, when the two dark solitons are launched towards each other in tilted angles heading for a collision, the solitons in the saturable nonlinear media could not survive through a collision above a critical background intensity (although they survive below that critical intensity value). This is in contrast to the Kerr law nonlinearity.