Fig. 18. Freeform all-area optimization methods and the design flows.
a Comparison between conventional (left) and freeform (right) design schemes. Reproduced with permission189. Copyright 2022, The Authors, published by De Gruyter. b A grid representation (left) approaching a faithful representation that coincides with the whole device design space (right). In a faithful representation (middle). Reproduced with permission189. Copyright 2022, The Authors, published by De Gruyter. c Metasurface design procedure using couple-mode-theory (CMT) and adjoint optimization. Reproduced with permission191. Copyright 2020, The Authors, published by Springer Nature. d Schematic of a global population-based optimizer for metagrating optimization. Reproduced with permission193. Copyright 2019, American Chemical Society