Stable (2+1)-dimensional solitons in a layered medium with sign-alternating Kerr nonlinearity

Transverse beam propagation is considered in a layered structure in which Kerr nonlinearity alternates between self-focusing and self-defocusing, which makes it possible to prevent collapse. A structure composed of alternating self-focusing layers with strongly different values of the Kerr coefficient is considered too. By means of both a variational approximation (which is implemented in a completely analytical form, including the stability analysis) and direct simulations, it is demonstrated that stable quasi-stationary (2 + 1)-dimensional soliton beams exist in these media (direct simulations demonstrate stable propagation over a distance exceeding 100 diffraction lengths of the beam). Quasi-stationary cylindrical solitons with intrinsic vorticity exist too, but they all are unstable, splitting into separating zero-vorticity beams. (C) 2002 Optical Society of America.