Design characteristics of photonic antennas for wireless optical communication

We present and extend simple design criteria to investigate the radiation characteristics of photonic antennas, which transfer the energy of a beam out of an optical waveguide. As applicable examples, we evaluate gratings having symmetric or asymmetric groove shape and offer their explicit formulas for the leakage parameters of photonic antennas. The results covered only TE modes reveal that, by judiciously designing the grating profile, it is possible to achieve high directional operation of photonic antennas in the range of optical frequency. Especially, particular attention is given to asymmetric triangular profiles because the directional efficiency is averagely over 80% and becomes 99% at a specific condition.