We uncover a strong coupling between nonlinearity and diffraction in a photonic crystal at the supercollimation point. We show that this is modeled by a nonlinear diffraction term in a nonlinear-Schrödinger-type equation in which the properties of solitons are investigated. Linear stability analysis shows solitons are stable in an existence domain that obeys the Vakhitov–Kolokolov criterium. In addition, we investigate the influence of the nonlinear diffraction on soliton collision scenarios.
Xu, Z., Maes, B., Jiang, X., Joannopoulos, J., Torner, L., Soljacic, M. Nonlinear photonic crystals near the supercollimation point. "Optics letters", Agost 2008, vol. 33, núm. 15, p. 1762-1764.