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

Dynamic radiative cooling attracts fast-increasing interest due to its adaptability to changing environment and promises for more energy-savings than the static counterpart. Here we demonstrate enhanced infrared emission by thermally switching the excitation of magnetic polariton with microstructured vanadium dioxide (VO₂) metasurfaces fabricated via scalable and etch-free processes. Temperature-dependent infrared spectroscopy clearly shows that the spectral emittance of fabricated tunable metasurfaces at wavelengths from 2 to 6 μm is significantly enhanced when heated beyond its phase transition temperature, where the magnetic polariton is excited with metallic VO₂. The tunable emittance spectra are also demonstrated to be insensitive to incidence and polarization angles such that the VO₂ metasurface can be treated as a diffuse infrared emitter. Numerical optical simulation and analytical inductance-capacitance model elucidate the suppression or excitation of magnetic polariton with insulating or metallic VO₂ upon phase transition. The effect of enhanced thermal emission with the tunable VO₂ metasurface is experimentally demonstrated with a thermal vacuum test. For the same heating power of 0.2 W, the steady-state temperature of the tunable VO₂ metasurface emitter after phase transition is found to be 20 °C lower than that of a reference V₂O₅ emitter whose static spectral emittance is almost the same as that of the VO₂ metasurface before phase transition. The radiative thermal conductance for the tunable metasurface emitter is found to be 3.96 W/m²K with metallic VO₂ at higher temperatures and 0.68 W/m²K with insulating VO₂ at lower temperatures, clearly demonstrating almost 6-fold enhancement in radiative heat dissipation.