  We discover that at the edge of optical lattice imprinted in saturable
nonlinear media one-dimensional surface solitons exist only within a band of
light intensities, and that they cease to exist when the lattice depth exceeds
an upper threshold. We also reveal the generation of arrays of two-dimensional
surface solitons mediated by transverse modulational instability of
one-dimensional solitons, a process that is found to exhibit specific features
associated to properties of the optical lattice.
