Solitary-wave vortices in type II second-harmonic generation

We find families of optical bright, vortex solitary waves in bulk quadratic nonlinear media under conditions for type II second-harmonic generation. We study the main properties of the families of solitary waves, including their stability. The vortex solitary waves are found to be azimuthally unstable and their decay into sets of stable spatial solitons is shown. We calculate the growth rates of the possible azimuthal perturbations with different azimuthal index and show how those affect the pattern of output light. Numerical simulations to check the predictions of the stability analysis are also reported. (C) 1998 Elsevier Science B.V.