Coloured conical emission via second-harmonic generation
  We predict that the combination of space and time modulational instabilities occuring via parametric wave-mixing in quadratic media leads to coloured conical emission. This phenomenon should be observed under conditions usually employed in second-harmonic generation experiments. 
S. Trillo, C. Conti, P. Di Trapani, O. Jedrkiewicz, J. Trull, G.   Valiulis, G. Bellanca