WAVE COLLAPSE IN BULK MEDIA WITH QUADRATIC AND CUBIC RESPONSES

The mutual influence of quadratic and cubic nonlinearities on the prop agation of coupled fundamental and second harmonic waves in optical me dia is studied. Particular attention is paid to the self-focusing of C W Gaussian beams in bull media. Such beams are found to self-focus unt il collapse, whenever their power exceeds a threshold value. We determ ine this threshold power and find its dependence on the strength of th e quadratic and cubic nonlinearities and on the phase mismatch. (C) 19 98 Elsevier Science B.V.