We report the first experimental demonstration of two-dimensional spatial solitary waves in second-order nonlinear optical material. When an intense optical beam is focused into a phase-matchable second-order nonlinear material, the fundamental and generated second-harmonic fields are mutually trapped as a result of the strong nonlinear coupling which counteracts both diffraction and beam walkoff.
Torruellas, W., Wang, Z., Hagan, D., VanStryland, E., Stegeman, G., Torner, L., Menyuk, C. Observation of two-dimensional spatial solitary waves in a quadratic medium.. "Physical review letters", Juny 1995, vol. 74, núm. 25, p. 5036-5039.