FDTD Simulation of Near-Field Radiative Heat Transfer between Thin Films Supporting Surface Phonon Polaritons: Lessons Learned

Abstract

Abstract We present the numerical simulation, using the finite difference time domain (FDTD) method, of the radiative heat transfer between two thin SiC slabs. We aim to explore the ability of the FDTD method to reproduce the analytical results for the Surface Phonon Polariton (SPhP) assisted near field radiative energy transfer between two SiC slabs separated by a nano/micro-metric vacuum gap. In this regard, we describe the key challenges that must be addressed for simulating general near-field radiative energy transfer problems using the FDTD method. FDTD is a powerful technique for simulating the near-field radiative energy transfer because it allows simulating arbitrary shaped nano-structured bodies, like photonic crystals, for which an analytical solution is not readily obtained. Key words : Near-Field Radiative Heat Transfer, Fluctuation Electrodynamics, Thermal Radiation, Surface Phonon Polariton, FDTD 1. Introduction When two bodies are located at short distance (in the nano/micro scale) the evanescent modes can tunnel between each other and contribute to the radiative energy transfer, which can exceed the black body radiation by several orders of magnitude [1–3]. Besides, at nano-metric distance, the excitation of surface plasmon polaritons (SPP) in metals or surface phonon polaritons (SPhP) in polar materials, produce even further enhancement of the radiative energy transfer at the resonance frequencies [4–7], allowing for quasi-monochromatic near-field radiative heat transfer. These phenomena have got rising attention in the recent years due to the strong development of nano/micro-technologies, where near-field effects have to be considered in the thermal analysis. Some of the key applications that has been proposed so far are nano-lithography [8], near-field imaging [9], thermophotonic heat pumping [10], and thermophotovoltaic (TPV) energy conversion [3], [11–16] . Most of the theoretical studies on near-field radiative heat transfer presented so far are based on fluctuation electrodynamics theory [17–19]. This theoretical framework assumes that the origins of thermal radiation are the fluctuating currents originated by the random motion of charges within the material, and the problem can be solved analytically by means of the Green’s functions [20], which provides the spatial transfer function between current sources and the corresponding electro-magnetic fields in a given location of the space. However, the complexity of Green’s function formalism limits the theoretical development on near-field radiative heat transfer to relatively simple geometries; mainly infinite extended multilayered structures [19], for which a closed analytical solution is available.