Fig. 4: Distributed Gradient-based optimization improvement of metalens design.
From: Low-overhead distribution strategy for simulation and optimization of large-area metasurfaces
a Lens efficiency versus optimization iteration, where lens efficiency is defined as the ratio of the power within a circle of radius 3 × FWHM in the focal plane to the power incident on the metasurface. The initial metasurface is a 30 μm × 30 μm metalens with focal-length 20 μm designed from the low aspect-ratio scatterer library used in Fig. 3b using the traditional periodic-approximation metasurface design approach. The metalens is designed and optimized for x-polarized light only. In 35 optimization iterations, the metalens efficiency is almost doubled. The inset shows the intensity of the X-component of the electric field in the focal plane before optimization (left) and after optimization (right). b Schematic of the cylindrical metasurface scatterers after optimization. c Histograms of the distance between the final scatterer positions and the initial scatterer positions (left) and the absolute radius difference between the final scatterer cylinders and the initial scatterer cylinders (right). As can be seen in these histograms, both the scatterer positions and radii change as a result of the optimization.
