Multicharged vortex evolution in seeded second-harmonic generation

We show the dynamics of the evolution of screw phase dislocations in the wa ve fronts of Gaussian beams with nested multiple-charged vortices that prop agate in quadratic nonlinear crystals under conditions for seeded second-ha rmonic generation. The number of existing vortices is shown to depend on th e input light and material conditions, including the topological charge, th e width and intensity of the pump and seed signals, and the propagation len gth inside the crystal. A closed-form model, which holds for arbitrary topo logical charges of the pump and seed inputs under conditions of negligible depletion of the pump beam, is developed to predict the number of vortices that exist at any instant in the propagation. It is discovered that differe nt combinations of input charges yield a fascinating variety of vortex patt erns. (C) 2000 Optical Society of America [S-740-3224(00)00407-0].