Highly efficient directional emission using a coupled multi-channel structure to a photonic crystal waveguide with surface modification

We propose a system for achieving highly efficient directional emission using a coupled multi-channel structure to a photonic crystal waveguide with a modified surface region. A highly directional beam with about 50% transmission efficiency at large distances can be obtained. The simulation results show that the surface modes in the modified region are easy to couple to the multi-channel structure, which can generate many light beams in the channels. The interference of the light beams exiting from the channels results in a highly efficient directional emission. Additionally, the size effect of the coupled multi-channel structure on the directional emission is also considered. When the row number of the coupled multi-channel structure is larger than a certain value, a steady state of highly efficient directional emission can be obtained