Discrete and surface solitons in photonic graphene nanoribbons

We analyze localization of light in honeycomb photonic lattices restricted in one dimension which can be regarded as an optical analog of (``armchair'' and ``zigzag'') graphene nanoribbons. We find the conditions for the existence of spatially localized states and discuss the effect of lattice topology on the properties of discrete solitons excited inside the lattice and at its edges. In particular, we discover a novel type of soliton bistability, the so-called geometry-induced bistability, in the lattices of a finite extent.