Tunable negative refraction in optical lattices

Propagation of beams in photonic structures with a periodic modulation of the refractive index is defined through the diffraction properties of the extended eigenmodes in the form of Bloch waves. At the boundaries of the structure, beams experience refraction. In this work, we study theoretically and demonstrate experimentally the control over the refraction of beams by a tilted optical lattice of variable depth. We realize dynamic tunability of beam refraction and perform controlled beam steering.