Four-wave mixing and walk-off between two optical beams are! investigated For focusing Kerr media. It is shown that four-wave mixing reinforces the self-focusing of mutually trapped waves by lowering their power threshold for collapse, only when their phase mismatch is small. On the contrary, walk-off inhibits the collapse by detrapping the beams, whose partial centroids experience nonlinear oscillations.
Physical Review Letters, 2000, Vol 84, Issue 15, p. 3302-3305