Metasurfaces as artificial crystals for electromagnetic polarization handling

Metasurfaces acting on electromagnetic fields have emerged as powerful tools that can address all the wave's degrees of freedom: amplitude, phase and polarization. It is especially with respect to polarization that their role is steadily growing: metasurfaces can indeed perform, by design, operations that would usually require very specific, delicate and expensive natural or synthetic ordinary crystals. Here, I will first briefly review the history of light polarization, and its connection with ordinary crystals. Subsequently, I will highlight in which sense metasurfaces are artificial quasi-two-dimensional crystals, evidencing their potential as future polarization-handling (meta) materials.