Fig. 12
From: Planar metasurface-based concentrators for solar energy harvest: from theory to engineering
(a) (I) Schematic showing the production of meta-lenses at low cost and high yield using existing photolithographic stepper technology. The pattern of the meta-lens contained in the reticle was then projected using the stepper, and rapidly replicated over the face of the wafer by repeatedly exposing and incrementally stepping the wafer position. An SEM of the meta-lens center (center right) shows the microscopic posts. (II) The fabricated meta-lens for imaging. (III) Image of focal spot with 7 mm Gaussian illumination at 1550 nm. (b) (I) Fabrication process of the designed meta-lens using the selective etching process. (II) Zoom-in SEM image (tiled) of nanopillars of the meta-lens with a sidewall angle of 2.85°. (III) Top view SEM image near the center, and the inset shows the image of the edge of the lens. (IV) Image of 45 fabricated 1 cm meta-lenses on a 4-in.-diameter SiO2 wafer, focusing incident light on a white sheet of paper. (a) Reproduced with permission [206]. Copyright 2018, OSA. (b) Reproduced with permission [219]. Copyright 2019, ACS