Tunable negative refraction of light in photonic lattices

Negative refraction is a fundamental physical phenomenon that may occur in different systems as a result of anisotropy or periodicity. Periodic structures such as photonic crystals provide an invaluable opportunity to engineer the dispersion and diffraction properties of light. When light bends at the interfaces between homogeneous and periodic media, the refraction angle depends on the effective diffraction coefficients of the Bloch waves propagating inside the periodic structures. the beam refraction associated with the top of the first band is smaller than the lattice tilt, while for the beams associated with the edges of the bragg-reflection gap, refraction is strongly increased.