Interaction between multiple spatial solitons in the diffraction catastrophe region upon focusing a high-power laser beam in a nonlinear medium

When a high-power laser beam is focused in a nonlinear Kerr medium, beam se lf-diffraction by induced inhomogeneities of the refractive index is observ ed. A method for calculating the field amplitude and phase in the focal reg ion with regard for self-diffraction by self-induced inhomogeneities is dev eloped. Computer analysis of saturable Kerr media showed that the optical-f ield region with the least cross section of the focal pattern is followed b y that of chaotically radiating "splashes" and long filaments. The latter r adiate outward from the region of the caustic waist over long distances. Th ey represent bright spatial solitons, which channel a significant portion o f the primary beam energy. No less than 8-12 clear-cut solitons traveling i n the positive z direction and moving apart in the transverse (x, y) plane are observed in the cross section. The field amplitude oscillates along eac h of the solitons. Various parameters of the saturable Kerr medium are take n into account. (C) 2001 MAIK "Nauka/Interperiodica".