We report on the experimental observation of two-dimensional surface waves
localized at the edge or in the corner of femtosecond laser-written waveguide
arrays in fused silica. Increasing the power of the input beam allows one to
observe a clear transition from a linear diffraction pattern to localized
nonlinear surface states, which can exist at the interface only above a certain
power threshold.Comment: 13 pages, 4 figure
