  We observe experimentally two-dimensional solitons in superlattices
comprising alternating deep and shallow waveguides fabricated via the
femtosecond laser direct writing technique. We find that the symmetry of linear
diffraction patterns as well as soliton shapes and threshold powers largely
differ for excitations centered on deep and shallow sites. Thus, bulk and
surface solitons centered on deep waveguides require much lower powers than
their counterparts on shallow sites.
