Tunable beam propagating characteristics of two-dimensional rectangular-rod photonic crystals based on self-collimation effect

The light beam transmission characteristics of the two-dimensional photonic crystal structures consisting of a square lattice of rectangular dielectric rods are studied. Through optimizing the parameters of the structure, the self-collimated light propagation within a large frequency region is achieved, and the corresponding light propagation direction can be altered through rotating the rectangular rods in the square lattice, which is explained by the analysis of the equi-frequency surface contours. A compound structure composed of rectangular rods with different rotating angles is proposed in this paper, which has different kind of functions depending on the incident light beam's spatial width and incident location. The single-channel collimating propagation with different forward directions, two-branch-channel splitting with adjustable energy ratio, three-branch-channel splitting with different output beams' propagation directions can all be achieved. These kinds of devices can help expand the application of energy beam splitters in the optical circuits system and realize miniaturization integration.