  The flatness, compactness and high-capacity data storage capability make
metasurfaces well-suited for holographic information recording and generation.
However, most of the metasurface holograms are static, not allowing a dynamic
modification of the phase profile after fabrication. Here, we propose and
demonstrate a dynamic metasurface hologram by utilizing hierarchical reaction
kinetics of magnesium upon a hydrogenation/dehydrogenation process. The
metasurface is composed of composite gold/magnesium V-shaped nanoantennas as
building blocks, leading to a reconfigurable phase profile in a hydrogen/oxygen
environment. We have developed an iterative hologram algorithm based on the
Fidoc method to build up a quantified phase relation, which allows the
reconfigurable phase profile to reshape the reconstructed image. Such a
strategy introduces actively controllable dynamic pixels through a
hydrogen-regulated chemical process, showing unprecedented potentials for
optical encryption, information processing and dynamic holographic image
alteration.
