We report on the experimental observation of two-dimensional surface solitonsresiding at the interface between a homogeneous square lattice and asuperlattice that consists of alternating "deep" and "shallow" waveguides. Byexciting single waveguides in the first row of the superlattice, we show thatsolitons centered on deep sites require much lower powers than their respectivecounterparts centered on shallow sites. Despite the fact that the averagerefractive index of the superlattice waveguides is equal to the refractiveindex of the homogeneous lattice, the interface results in clearly asymmetricoutput patterns.
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