All Dielectric Mode Order Transformation Photonic Structure Design by Evolutionary Optimization Approach

In this manuscript, an evolutionary algorithm is applied to design a mode order converter photonic crystal structure for achieving transformation of the propagating fundamental mode to the higher order mode. In order to transform incident light mode from an even mode to an odd mode, predefined mask object functions are employed. The cross-sectional field profiles at the output face of the optimized structure are utilized to evaluate the optimization cost function to achieve mode order transformation task. In the study, the optimized structure composed of dielectric alumina (Al2O3) rods and time domain analyses of the optimization process are done by using finite-difference time domain method. Furthermore, numerical results are confirmed by experiments for designed structure at the microwave frequencies. It is shown that the numerical calculations and experimental measurements agree well with each other.