Bloch wavepacket control in truncated modulated optical lattices

We study the reflection of Bloch wavepackets at the interface of optical lattice possessing a shallow longitudinal out-of-phase refractive index modulation in adjacent waveguides. We show that the relation between the transmitted and reflected energy flows can be efficiently controlled by tuning the frequency and the depth of the modulation. Thus, complete beam reflection may be achieved for a set of resonant modulation frequencies at which light tunneling between adjacent guides of modulated lattice is inhibited.