The properties of the multi-quadratic-soliton generation process have been investigated both theoretically and experimentally near and on phase-match in non-critically-phase-matched, periodically poled, potassium titanyl phosphate (PPKTP). It was found that multi-soliton generation occurs primarily due to asymmetry in the input beam and at phase-matching. The number of solitons generated depended on the input intensity in a non-trivial way.
Polyakov, S., Jankovic, L., Kim, H., Stegeman, G., Carrasco, S., Torner, L., Katz, M. Properties of quadratic multi-soliton generation near phase-match in PPKTP. "Optics express", Juny 2003, vol. 11, núm. 11, p. 1328-1337.