Asymmetric light propagation in transverse separation modulated photonic lattices.

We investigate, both theoretically and numerically, the asymmetric light propagation in transverse separation modulated photonic lattices. The theoretical results show that the transmission contrast η of the structure is determined only by the coupling strengths between the chirped lattice and the two boundary uniform lattice portions. The numerical studies demonstrate that η is independent of the separation modulation function of the chirped lattice, which is in good agreement with the theory.