Cooling Metals via Gap Plasmon Resonance.

We report highly emissive and radiatively cooled metallic surfaces that sustain multiple and high-amplitude gap plasmon cavity modes within the principal thermal radiation spectrum at room temperature (i.e., 8-13 μm). A square-lattice array of Cu/ZnS/Cu gap plasmon cavities with five different widths was designed to avoid the near-field coupling between adjacent cavities and the anticrossing of a cavity mode and the first diffraction mode. The gap plasmon cavities fabricated on a Si substrate exhibited an effective emissivity of >0.62, up to an incidence of 60°. Outdoor solar heating experiments showed that the Cu/ZnS/Cu multicavity array lowered the Si substrate temperature by 4 °C at a maximum solar irradiance of 800 W/m2, which is equivalent to a near-one-sun intensity, relative to a planar Cu/ZnS/Cu multilayer. Such mid-infrared spectrum management of metals enables heat dissipation via radiation, which will be further utilized for designing electrodes that cool optoelectronic devices with the same metal/dielectric/metal configuration.