Fig. 3
Broken translational symmetry in thermal photonics. a Aperiodic multilayers for radiative cooling applications. Non-zero imaginary refractive indexes in HfO2 and SiO2 layers are responsible for a large emissivity in the atmospheric window. b Quasicrystalline-structured silicon films-based broadband absorber. c The bull’s eye structure and its angular-dependent emissivity. The highly directional and narrow emission peak (black line, right panel) is observed in the normal direction. d Alumina nanoparticles bonded nanosilk fabrics for daytime radiative cooling applications. e SiO2 microsphere doped polymer for daytime radiative cooling applications. The color map in the left panel shows the directional scattering of a single SiO2 microsphere. Figures adapted from: a, ref [40]; b, ref [47]; c, ref [50]; d, ref [52]; e, ref [53]