Inverse Design Strategies for Large Passive Waveguide Structures

Inverse design in photonics, the automated design of components by performance target specification, suffers from heavy computational requirements and extensive parameter spaces for large photonic components. Due to larger dimensions of the devices, the parameter space increases so that the optimization method has to tackle with an increased amount of local optima. Here, two inverse design strategies with the focus to improve inverse design for large passive waveguide structures are presented: Adaptive Threshold Binarization and Hybrid Optimization. Both reduce the probability of converging to poor local optima. With the presented design strategies inverse design is now applicable on waveguide structures with mode field diameters > 1~ mm and lengths of several hundred micrometers. In order to demonstrate its capability, the inverse design method is applied to the InP waveguide platform for the first time. As an example, a polarization mode filter design with -19.4 dB polarization extinction ratio (PER) is presented.