We report on the experimental observation of two-dimensional solitons located in defect channels at the surface of a hexagonal waveguide array. The threshold power for the excitation of solitons existing owing to total internal reflection grows with decrease of the refractive index in negative defects and vanishes for sufficiently strong positive defects. Negative defects can also support linear surface modes existing owing to Bragg-type reflections.
Szameit, A., Kartashov, Y.V., Heinrich, M., Dreisow, F., Pertsch, T., Nolte, S., Tunnermann, A., Lederer, F., Vysloukh, V.A., Torner, L. Observation of two-dimensional defect surface solitons. "Optics letters", Març 2009, vol. 34, núm. 6, p. 797-799.