Ultra-refraction phenomena in Bragg mirrors
  We show numerically for the first time that ultra-refractive phenomena do exist in one-dimensional photonic crystals: we exhibit the main features of ultra-refraction, that is the enlargement and the splitting of an incident beam. We give a very simple explanation of these phenomena in terms of the photonic band structure of these media. 
Didier Felbacq, Brahim Guizal, Frederic Zolla