Shaping solitons by lattice defects

Abstract

We demonstrate the existence of shape-preserving self-localized nonlinear modes in a two-dimensional photonic lattice with a flat-topped defect that covers several lattice sites. The balance of diffraction, defocusing nonlinearity, and optical potential induced by lattices with various forms of defects results in novel families of solitons featuring salient properties. We show that the soliton shape can be controlled by varying the shape of lattice defects. The existence domains of fundamental and vortex solitons in the semi-infinite gap expand with the defect amplitude. Vortex solitons in the semi-infinite gap with rectangular intensity distributions will break into dipole solitons when the propagation constant exceeds a critical value. In the semi-infinite and first-finite gaps, we find that lattices with rectangular defects can support stable vortex solitons which exhibit noncanonical phase structure.