Two-dimensional Nonlinear Optically-induced Photonic Lattices in Photorefractive Crystals

We study theoretically and generate experimentally two-dimensional nonlinear optically-induced photonic lattices with periodic phase modulation of different geometries in a photorefractive medium, including the periodic nonlinear waves with an internal energy flow or vortex lattices. We demonstrate that the light-induced periodically modulated nonlinear refractive index is highly anisotropic and nonlocal, and it depends on the orientation of a two-dimensional lattice relative to the crystal axis. We discuss stability of such optically-induced photonic two-dimensional structures and demonstrate experimentally their waveguiding properties