  We demonstrate a broadband, polarization independent, omnidirectional
absorber based on a metallic metasurface architecture, which accomplishes
greater than 90% absorptance in the visible and near-infrared range of the
solar spectrum, and exhibits low emissivity at mid- and far-infrared
wavelengths. The complex unit cell of the metasurface solar absorber consists
of eight pairs of gold nano-resonators that are separated from a gold ground
plane by a thin silicon dioxide spacer. Our experimental measurements reveal
high-performance absorption over a wide range of incidence angles for both s-
and p-polarizations. We also investigate numerically the frequency-dependent
field and current distributions to elucidate how the absorption occurs within
the metasurface structure. Furthermore, we discuss the potential use of our
metasurface absorber design in solar thermophotovoltaics by exploiting
refractory plasmonic materials.
