Topology optimization for transient response of photonic crystal structures

An optimization scheme based on topology optimization for transient response of photonic crystal structures is developed. The system response is obtained by a finite-element time-domain analysis employing perfectly matched layers as an absorbing boundary condition. As an example a waveguide-side-coupled microcavity is designed. The gradient-based optimization technique is applied to redistribute the material inside the microcavity such that the Q factors of a monopole and a dipole mode are improved by 375% and 285%, respectively, while maintaining strong coupling. This is obtained by maximizing the stored energy inside the microcavity in the decaying regime of the transient response. Manufacturable designs are achieved by filtering techniques capable of controlling minimum length scales of the design features. (C) 2010 Optical Society of America