Fig. 4. Metasurface-based dynamic geometric codes.
(A) Chart of the geometric codes for 0 to 9. (B) Reconstructed holographic image of 1. Each Arabic number in the chart can be expressed by a specific holographic image reconstructed from the same metasurface multiplexed by three sets of pixels: P1 (Mg/Pd), P2 (Au), and P3 (Mg/Pd/Cr). To achieve holograms with uniform intensity distributions, P2 is used twice in each unit cell. (C) Helicity of light, H2, O2, and reaction duration constitute multiple keys to generate the numbers 0 to 9, which are transformable with the same metasurface. The centrosymmetry point is indicated by a white circle in each plot, highlighting the location of the zero-order reflected light. A coding rule is defined that each number corresponds to a union set of the two holographic patterns in zones I and II.