  Structural colors generated due to light scattering from static
all-dielectric metasurfaces have successfully enabled high-resolution,
high-saturation and wide-gamut color printing applications. Despite recent
advances, most demonstrations of these structure-dependent colors lack
post-fabrication tunability that hinders their applicability for front-end
dynamic display technologies. Phase-change materials (PCMs), with significant
contrast of their optical properties between their amorphous and crystalline
states, have demonstrated promising potentials in reconfigurable nanophotonics.
Herein, we leverage a tunable all-dielectric reflective metasurface made of a
newly emerged class of low-loss optical PCMs with superb characteristics, i.e.,
antimony trisulphide (Sb$_2$S$_3$), antimony triselenide (Sb$_2$Se$_3$), and
binary germanium-doped selenide (GeSe$_3$), to realize switchable,
high-saturation, high-efficiency and high-resolution structural colors. Having
polarization sensitive building blocks, the presented metasurface can generate
two different colors when illuminated by two orthogonally polarized incident
beams. Such degrees of freedom (i.e., structural state and polarization) enable
a single reconfigurable metasurface with fixed geometrical parameters to
generate four distinct wide-gamut colors suitable for a wide range of
applications, including tunable full-color printing and displays, information
encryption, and anti-counterfeiting.
