Spectrally tunable nanocomposite metamaterials as near-perfect emitters for mid-infrared thermal radiation management.

Metamaterial emitters with spectrally tunable radiation in the mid-infrared region have aroused great interest in thermal management engineering applications. Nevertheless, it is still a great challenge to economically and conveniently manufacture easily scalable thermal emitters with wide-range tunable spectra. This work theoretically and experimentally demonstrates a conceptually simple and absorption-tunable design strategy for thermal emitters with tailorable spectral responses in the mid-infrared wavelength, based on the nanocomposite structure. This strategy introduces aluminum-doped zinc oxide (AZO) nanoparticles with intrinsic resonance into the top layer as an improvement to the traditional Fabry-Perot resonance system, and thereby excellent permittivity properties that are inaccessible to natural materials are obtained. With a field build-up generated in not just the middle spacer but also the top nanocomposite layer, the absorption bands can be tailored in a wider range. Moreover, according to the calculated relationship between the overall absorption and structural parameters, the tailorability of the absorption spectra can be achieved. As a proof of concept, infrared stealth and day-time radiative cooling performances are demonstrated based on spectrally different infrared emitters. This design and theoretical strategy leads to multipurpose metamaterials with tunable resonance responses for advanced thermal management engineering or even beyond infrared fields.