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Dynamic radiative cooling attracts fast-increasing interest due to itsadaptability to changing environment and promises for more energy-savings thanthe static counterpart. Here we demonstrate enhanced infrared emission bythermally switching the excitation of magnetic polariton with microstructuredvanadium dioxide (VO2) metasurfaces fabricated via scalable and etch-freeprocesses. Temperature-dependent infrared spectroscopy clearly shows that thespectral emittance of fabricated tunable metasurfaces at wavelengths from 2 to6 um is significantly enhanced when heated beyond its phase transitiontemperature, where the magnetic polariton is excited with metallic VO2. Thetunable emittance spectra are also demonstrated to be insensitive to incidenceand polarization angles such that the VO2 metasurface can be treated as adiffuse infrared emitter. Numerical optical simulation and analyticalinductance-capacitance model elucidate the suppression or excitation ofmagnetic polariton with insulating or metallic VO2 upon phase transition. Theeffect of enhanced thermal emission with the tunable VO2 metasurface isexperimentally demonstrated with a thermal vacuum test. For the same heatingpower of 0.2 W, the steady-state temperature of the tunable VO2 metasurfaceemitter after phase transition is found to be 20degC lower than that of areference V2O5 emitter whose static spectral emittance is almost the same asthat of the VO2 metasurface before phase transition. The radiative thermalconductance for the tunable metasurface emitter is found to be 3.96 W/m2K withmetallic VO2 at higher temperatures and 0.68 W/m2K with insulating VO2 at lowertemperatures, clearly demonstrating almost six-fold enhancement in radiativeheat dissipation.

Enhanced Infrared Emission by Thermally Switching the Excitation of Magnetic Polariton with Scalable Microstructured VO2 Metasurfaces