Fig. 1. Schematic of the metasurface device for generating color-selective 3D polarization structures.

Here, a 3-foil knot (knot 1), a 4-foil knot (knot 2), and a 5-foil knot (knot 3) are selected as complex polarization structures. Knots 1, 2, and 3 are predesigned polarization structures in the same observation region for the wavelengths of 650, 575, and 500 nm, respectively. The polarization directions of points on the 3D knots are denoted with yellow arrows. Both polarization and color information (wavelength) of these three knots are encoded into a single metasurface consisting of gold nanorods. a–c The measured intensity profiles upon the illumination of a horizontal LP light beam before and d–f after passing through a polarizer (analyzer). a and d are generated at λ = 650 nm, b and e at λ = 575 nm, and c and f at λ = 500 nm in the same observation plane of z = 500 μm. The intensity profiles d–f correspond to the analyzer with a transmission axis along the vertical direction