Enhanced stability of nonlocal solitons in saturable focusing media

In many optical systems the nonlinear response of the medium is actually a spatially nonlocal function of the wave intensity. This means that the index change in a particular point depends on the light intensity in a certain neighborhood of this point. This occurs, for instance, when the nonlinearity is associated with some sort of transport processes, such as heat conduction, diffusion of charge carriers or atoms or molecules in vapors. It is also the case in systems exhibiting a long-range interaction of constituent molecules or particles, such as in nematic liquid crystals or dipolar Bose Einstein condensates. Nonlocality is thus a feature of a large number of nonlinear systems leading to novel phenomena of a generic nature.