Asymmetric CycleGANs for inverse design of photonic metastructures

Using deep learning to develop nanophotonic structures has been an active field of research in recent years to reduce the time intensive iterative solutions found in finite-difference time-domain simulations. Existing work has primarily used a specific type of generative network: conditional deep convolutional generative adversarial networks. However, these networks have issues with producing clear optical structures in image files; for example, a large number of images show speckled noise, which often results in non-manufacturable structures. Here, we report the first use of cycle-consistent generative adversarial networks to design nanophotonic structures. This approach significantly reduces the amount of speckled noise present in generated geometric structures and allows shapes to have clear edges. We demonstrate that for a given input reflectance spectra, the system generates designs in the form of images, and a complementary network generates reflectance spectra if an image containing a shape is provided as an input. The results show a higher Frechet Inception Distance score than previous approaches, which indicates that the generated structures are of higher quality and are able to learn nonlinear relationships between both datasets. This method of designing nanophotonics provides alternative avenues for development that are more noise robust while still adhering to desired optical properties.