Fig. 2. Unit cell and design plots for a multiwavelength metaoptic based on nanoposts.

a Schematic of a bilayer metasurface unit cell consisting of amorphous silicon nanoposts vertically stacked in close proximity. The nanoposts have a height of 750 nm and are arranged in a square lattice with a period of 600 nm and embedded in a PDMS layer. The transmission coefficient (t) of the bilayer is calculated as the product of the transmission coefficients of each individual layer (t₁ and t₂). b, c Design plots showing the corresponding radii in layer 1 (r₁) and layer 2 (r₂), as indicated by the color bars, for achieving all possible combinations of ϕ(λ₁) (the phase at 1180 nm) and ϕ(λ₂) (the phase at 1680 nm). d, e Corresponding transmission values (|t₁t₂|²) at 1180 nm d and 1680 nm e