Anomalous refraction and diffraction in discrete optical systems

Phys Rev Lett. 2002 Mar 4;88(9):093901. doi: 10.1103/PhysRevLett.88.093901. Epub 2002 Feb 12.

Abstract

We experimentally prove that light propagation in a discrete system, i.e., an array of coupled waveguides, exhibits striking anomalies. We show that refraction is restricted to a cone, irrespective of the initial tilt of the beam. Diffraction can be controlled in size and sign by the input conditions. Diffractive beam spreading can even be arrested and diverging light can be focused. The results can be thoroughly theoretically explained.