Directional emitter and beam splitter based on self-collimation effect

We present a self-collimation-based directional emitter and compact beam splitters in a two-dimensional photonic crystal by using the surface modification method. The simulation results show that highly directional emission with a small angular divergence is achieved over a relative bandwidth of about 10.2%. Furthermore, by only modifying the monolayer structure of the output surface, the compact beam splitters, including the Y-shaped, one-to-three, and one-to-five structures are realized. Such beam splitters have remarkable properties such as symmetrical energy distribution and high transmission.