Interface solitons in two-dimensional photonic lattices

We analyze localization of light at the interfaces separating square and hexagonal photonic lattices, as recently realized experimentally for two-dimensional laser-written waveguides in silica glass with self-focusing nonlinearity [Opt. Lett.33, 663 (2008)]. We find the conditions for the existence of linear and nonlinear surface states substantially influenced by the lattice topology, and study the effect of different symmetries and couplings on the stability of two-dimensional interface solitons.