  Plasmonic color generation utilizing ultra-thin metasurfaces as well as
metallic nanoparticles hold a great promise for a wide range of applications,
including color displays, data storage, and information encryption due to its
high spatial resolution and mechanical/chemical stability. Most of the recently
demonstrated systems generate static colors; however, more advanced
applications such as data storage require fast and flexible means to tune the
plasmonic colors, while keeping them vibrant and stable. Here, a surface-relief
aluminum metasurface that reflects polarization-tunable plasmonic colors is
designed and experimentally demonstrated. Excitation of localized surface
plasmons encodes discrete combinations of the incident and reflected polarized
light into diverse colors. A single storage unit - a nanopixel - stores a
multiple-bit piece of information in the orientation of its constituent
nanoantennae. This information is then reliably retrieved by inspecting the
reflected color sequence with two linear polarizers. It is the broad color
variability and high spatial resolution of the proposed encoding approach that
supports a strong promise for rapid parallel read-out and encryption of
high-density optical data. Our method also enables the robust generation of
dynamic kaleidoscopic images with no detrimental "cross-talk" effect. The
approach opens up a new route for advanced dynamic steganography, high-density
parallel-access optical data storage, and optical information encryption.
