Unidirectional light propagation in heterojunction photonic crystals

In this paper, we report numerical studies of unidirectional light propagation in a heterojunction photonic crystal waveguide (PCW). The proposed structure consists of two square- lattice photonic crystals and a coupling region. By careful design of this region placed at the interface of the PCs, the light wave propagation in one direction can be significantly enhanced and improved. Two line defects of different shapes are introduced along the interface to control and modify the propagation of the light. The findings may be implemented in integrated optical systems.