Directional localization of light rays in a periodic array of   retro-reflector lenses
  We show that vertical light rays in almost every periodic array of Eaton lenses do not leave certain strips of bounded width. The light rays are traced by leaves of a non-orientable foliation on a singular plane. We study the flow defined by the induced foliation on the orientation cover of the singular plane. The behavior of that flow and ultimately our claim for the light rays is based on an analysis of the Teichm\"uller flow and the Kontsevich-Zorich cocycle on the moduli space of two branched, two sheeted torus covers in genus two. 
Krzysztof Fraczek and Martin Schmoll
math.DS math-ph math.MP physics.optics