Enhanced tunneling distance of near field radiative energy with high-index dielectric resonators

Abstract

By placing high-index dielectric resonators on surfaces supporting surface plasmons in the near field, strong magnetic resonance can be observed in the high-index dielectric resonators with appropriate heights around the surface plasmon resonance frequencies. The strong magnetic resonance allows strong thermal photon tunneling across a 1 μm gap, which is one order longer than the previous demonstrations of near field radiation with surface plasmons. The thermal photon tunneling happens when the horizontal wavenumber is kx∼4πw with w is the width of the high-index resonators. The height of the high-index dielectric resonators should provide enough retardation of the electric field between the top and bottom of the resonator to form a displacement current loop. Therefore, similar magnetic field resonance occurs in the resonator when we triple rather than double the height of the high-index dielectric resonators. The usage of dielectric resonators to amplify the thermal electric field in the near field domain can be a potential method to increase the quasi-monochromatic radiation distance of an emission domain by one order or more at the frequencies of the surface waves.

Amplification of near field radiation at surfaces of pure dielectric domain with anti-reflection films and photonic crystal structures

“…Several different methods have been established to numerically calculate near-field radiative heat transfer. For convenience, we adopted a combination of the scattering matrix method and the Wiener-Chaos expansion method demonstrated in previous studies to solve Maxwell's equations having fluctuating thermal currents semi-analytically [8,13]. In this method, plane wave expansion is applied to decompose the electromagnetic fields into transverse electric (TE) and transverse magnetic (TM) modes.…”

“…It is well known that near-field thermal electric fields can be amplified at metallic surfaces at near infrared (IR) wavelengths with surface plasmon polariton, which can be harvested with PV cells. [7,8] However, metallic surfaces can suffer from oxidation even under a vacuum environment when temperatures are close to (or higher than) 1000 K. [9] Dielectric materials, on the other hand, can be chemically stable under high temperatures. However, intrinsic dielectric material does not support surface waves at near-infrared (near IR) wavelengths.…”