Tuning the spectrum of near-field radiative heat transfer using Mie resonance based metamaterials

Tuning the spectrum of near-field radiative heat transfer is crucial for many potential applications such as near-field thermophotovoltaic and thermophotonic power generation. Mie resonance based metamaterials are promising candidates for tuning the near-field spectra. In this manuscript, we utilize the Fourier modal method to perform nonapproximate simulations of near-field radiative heat flux between Mie resonance based metamaterials. By decomposing the electromagnetic response of the Mie resonators into contributions from various multipoles, we identify the origins of the peaks in the near-field spectra. We study the effect of the refractive index, extinction coefficient, shape, and interspacing of Mie resonators, as well as the separation distance of the metamaterials on the spectrum of near-field heat flux. Our study shows that as the refractive index of the metamaterial increases, the heat flux increases and the spectral locations of the Mie resonances redshift. As the extinction coefficient increases, the near-field heat flux increases and the damping of the Mie resonances eventually results in a broadband spectrum for the heat flux. Resonance splitting is observed when the distance between the Mie resonators approaches the nanometer scale. While the existing studies suggest that Mie resonance based metamaterials increase the near-field heat flux, the near-field heat transfer between these metamaterials is smaller than that between two thin films of the same material and thickness. However, Mie resonance based metamaterials are promising for tuning the spectrum of the near-field heat flux.