Design of two-dimensional photonic crystals with large absolute band gaps using a genetic algorithm

A two-stage genetic algorithm (GA) with a floating mutation probability is developed to design a two-dimensional (2D) photonic crystal of a square lattice with the maximal absolute band gap. The unit cell is divided equally into many square pixels, and each filling pattern of pixels with two dielectric materials corresponds to a chromosome consisting of binary digits 0 and 1. As a numerical example, the two-stage GA gives a 2D GaAs structure with a relative width of the absolute band gap of about $19%.$ After further optimization, a new 2D GaAs photonic crystal is found with an absolute band gap much larger than those reported before.