Fig. 2

Schematics of the metalens. (a) Schematic illustration of the optical behavior of the proposed see-through reflective metalens. (b) Schematic illustration of a unit cell of the metalens, consisting of a Si nanofin on the sapphire substrate with fixed length L, width W, height H, and period P, but varying rotation angle θ according to the Pancharatnam-Berry phase. (c) 1st order diffraction efficiencies of the reflected light, as the length and width of the nanofins vary while the height is fixed to be 230 nm. (d) 0th order transmission spectra of the meta-grating-cell, with the corresponding length × width of each nanofin labeled in the legends