Near- to far-field coherent thermal emission by surfaces coated by nanoparticles and the evaluation of effective medium theory

Near-field thermal radiation may play significant role in the enhancement of energy harvesting and radiative cooling by new types of designer materials, which in turn can be crucial in the development of future devices. In this work, we present a case study to explore near- to far-field thermal emission and radiative flux from a thin polar SiC film coated by different size and shape nanoparticles. The same geometry with nano-particles is also considered as a layered medium, which is analyzed using Effective Medium Theory (EMT). A significant enhancement of emission, particularly at the far infrared, is observed when nanoparticles are placed on the surface of a SiC film with certain periodicities, which shows potential use of these structures for radiative cooling applications. Yet, these enhancements are not observed when the EMT approach is adapted, which is questioned for its accuracy of predicting near-to-far field transition regime of radiation transfer from corrugated surfaces.