Directional emission from photonic crystal waveguide terminations using particle swarm optimization

We report particle swarm optimization (PSO) of photonic crystal (PC) structures through an example of a PC waveguide termination to achieve directional emission. PC waveguide termination is optimized by using the PSO algorithm by evaluating a fitness function by the scattering matrix method. We consider two different structures, reported earlier and designed through intuition and trial and error, for our optimization and compare the results obtained. Our results show that optimizing with PSO can provide more directed and intense beams compared with designs based purely on intuition and trial and error. Compared with the two earlier reported directional emission PC structures, increases in intensity by factors of 1.25 and 2 and decreases in beam divergence by factors of 1.25 and 2.4, respectively, were achieved.