Radiative heat transfer between multilayer hyperbolic materials in both near-field and far-field

Hyperbolic materials have attracted much attention in nanophotonics and thermal radiation because they can support high-wavevector modes. The near-field radiative heat transfer between single hyperbolic materials has been studied extensively, however, the radiative heat transfer (RHT) between multilayer hyperbolic materials in both near-field and far-field has seldomly been investigated. In this paper, we investigate the RHT between stacked structures consisting of two different hyperbolic materials in the near-field and far-field, taking uniaxial hBN, and biaxial α-MoO3 for instance. The influence of the arrangement and thicknesses of the two materials on the RHT have been fully studied. The numerical results demonstrate that the RHT is dominated by the substrate material of the stacked structures in the far-field, and the contribution of the hyperbolic film is limited. However, in the near-field, the RHT is dominated by the hyperbolic film. Besides, when the substrate material is hBN, the addition of α-MoO3 will greatly enhance the RHT. When the substrate is α-MoO3, the addition of hBN will be greatly suppressed. The performance of RHT in different cases is attributed to the coupling of hyperbolic polaritons supported by hBN and α-MoO3, which is verified by investigating the energy transmission coefficients. Our results in this work may guide us in designing the emitter and receiver based on hyperbolic materials when considering the RHT in both near-field and far-field.