  High performance metasurfaces for thermal radiative cooling applications can
be identified using computational optimization methods. This work has
identified an easy-to-fabricate temperature phase transition VO2 nanowire array
laid atop dielectric BaF2 Fabry-Perot cavity-on-metal with total coating
thickness of 2 um. This optimized structure has ability to self-adaptively
switch between high reflectance at low temperature to high emissivity at high
temperature in the broad thermal infrared spectrum. This design demonstrates
exceptional turn-down figure-of-merit compared to previously realized
configurations utilizing VO2 metasurfaces and multilayers. The mechanism is
achieved with a sub-wavelength nanowire array effective medium that switches
between anti-reflecting gradient coating and Fabry-Perot interference. This
thin metasurface coating could impact self-cooling of the solar cells,
batteries, and electrical devices where risk presents at high temperatures.
