Fig. 1. Working principle of the dynamic metasurface pixels.

(A) Schematic of hydrogen-responsive Mg nanorods (200 nm × 80 nm × 50 nm), which are sandwiched between a Ti (5 nm)/Pd (10 nm) capping layer and a Ti (3 nm) adhesion layer. (B) Measured scattering spectra of such a nanorod in Mg (on) and MgH₂ (off) states. Before hydrogenation, the Mg nanorod exhibits a strong plasmonic resonance (red curve), whereas after hydrogenation (10% H₂) the MgH₂ rod shows a nearly featureless spectrum (blue curve). The process is reversible through dehydrogenation using O₂ (20%). a.u., arbitrary units. (C) Simulated phase delay for the different phase levels. The orientation of the nanorod at each phase level is shown.