Apparent Spectral Shift of Thermally Generated Surface Phonon-Polariton Resonance Mediated by a Nonresonant Film

Abstract

Near-field radiative heat transfer between dissimilar materials is important in thermal management and energy-harvesting, but an in-depth physical analysis is needed. Using fluctuational electrodynamics, this study shows that the spectral redshift or blueshift of thermally generated surface phonon-polaritons (SPhPs) can be mediated by a nonresonant layer. The apparent shift is due to multiple reflections within the subwavelength gap separating resonant and nonresonant layers, which generate gap modes and decrease thermal emission around the SPhP resonance---valuable insight for applications based on near-field thermal radiation, such as thermophotovoltaics and thermal rectification.