Near-field radiative thermal transfer between a nanostructured periodic material and a planar substrate

Abstract

This paper provides a method based on rigorous coupled wave analysis for the calculation of the radiative thermal conductance between a layer that is patterned with arbitrary, periodically repeating features and a planar substrate. This method is applied to study the transfer from an array of beams with a rectangular cross section. The impact of the structure size and spacing on the thermal conductance are investigated. These calculations are compared to an effective medium theory, which becomes increasingly accurate as the structure sizes fall well below the relevant resonance wavelengths of materials and structures. Moreover, comparisons are made with a modified proximity approximation and the far-field approximation, which become valid for small and large spacings, respectively. Results show that new levels of control over the magnitude and spectral contributions to thermal conductance can be achieved with corrugated structures relative to planar ones. Specifically, we show for SiC arrays with rectangular cross sections and with the same filling fraction that the use of a smaller periodicity leads to a lowered far-field thermal transfer and an increased near-field thermal transfer. INTRODUCTION:

Focused thermal emission from a nanostructured SiC surface

“…There are already some calculations in this regard available in the literature 42 . Here, we leverage our previous works on thermal transfer calculations 43,44 to obtain an expression for the thermal emission pointing outward from the nanostructure at different heights from its surface. The presented analysis is valid for periodic structures.…”

“…By taking the limit of loss going to zero, we obtain the thermal emission of the periodic structure at this height. This provides a way to calculate the thermal emission at the height of interest based on the method that has already been developed for thermal transfer calculations between an arbitrarily shaped periodic structure and a planar substrate 43 . However, the final result can be further simplified by analytically taking the limit of zero loss in the hypothetical planar body.…”

“…For the general case of periodic structures (See Fig. 3), we can express the electromagnetic Green functions, representing the electromagnetic response of the system to electric dipoles, in terms of the response of the system to plane waves by using the modified version of Sipe's formalism 43,45 . We assumed the z direction to be toward the planar body and normal to its plane.…”

Enhancing near-field heat transfer between composite structures through strongly coupled surface modes

“…Because of the tunneling effect of evanescent waves, near-field thermal radiation can exceed the blackbody radiation limit, which is administrated by the well-known Planck's Law, by several orders of magnitude [1][2][3], especially when surface plasmon polaritons (SPPs) or surface phonon polaritons (SPhPs) are excited [4][5][6][7]. The enhancement and further manipulation of near-field heat transfer (NFHT) show promising wide-range applications, such as near-field thermophotovoltaics [8][9][10][11], noncontact refrigeration [12][13][14], near-field nanoimaging [15][16][17], and information processing [18,19].…”

Near-Field Thermal Radiation between Metasurfaces

“…However, theoretical investigations of macroscopic objects have been limited to planar or effectively planar geometries due to the lack of computing techniques, [29][30][31][32][33][34] until recently when patterned nanostructures are considered based on exact theories. [35][36][37][38][39][40][41][42][43][44] If bulk surface modes such as surface plasmon polaritons (SPPs) and surface phonon polaritons (SPhPs) are excited, the radiative heat flux can be further increased to be orders of magnitude higher than the far-field limit governed by the Stefan-Boltzmann law. 3 However, the frequency band of the resonance-based surface modes is narrow, inhibiting this simple configuration from achieving higher heat flux in certain applications including thermal management, although the efficiency of thermophotovoltaic devices could be better by using narrowband surface modes.…”