Nonlinear photonic lattices in anisotropic nonlocal self-focusing media
  We analyze theoretically and generate experimentally two-dimensional nonlinear periodic lattices in a photorefractive medium. We demonstrate that the light-induced periodically modulated nonlinear refractive index is highly anisotropic and nonlocal, and it depends on the lattice orientation relative to the crystal axis. We discuss stability of such induced photonic structures and their guiding properties. 
Anton S. Desyatnikov, Dragomir N. Neshev, Yuri S. Kivshar, Nina   Sagemerten, Denis Traeger, Johannes Jaegers, Cornelia Denz...