Keita Morimoto

In order to develop compact and high-performance photonic devices, optimal design methods using computer simulation for photonic devices have been actively developed. In particular, topology optimal design method, which can change topology of structure, has a potential to find completely novel structures that have never been considered. On the other hand, a global optimum solution is, in general, difficult to be find out in the topology optimal design method due to its high degree of freedom, and required time for design of 3D photonic devices increases dramatically compared with 2D design problems. In this study, in order to improve the efficiency of topology optimal design of 3D photonic devices, we propose an improved effective index method (EIM) for better 2D approximation of 3D structures. The design efficiency is improved by iteratively improving the designed 2D structure based on improved EIM by using 3D analysis. In 2D design with less computational effort, we utilize a topology optimal design method by combining evolutionary method and gradient method, to search global optimal solution efficiently.