5 μm Level Long Photon Tunneling Distance in Near Field Thermal Radiation Through Metallic Patterns With/Without Dielectric Structures

Abstract

By integrating wave-type analysis and fluctuation-dissipation theorem, the enhancement of photon tunneling distance in near field thermal radiation through metallic nanopatterns with/without dielectric structures is theoretically studied. When metallic patterns are in the immediate proximity of the conductive emitter, substantial thermal electric enhancement at surface plasmon frequency is observed between the metallic patterns and the emitter when the periodicity of the thermal electric field along the emitter surface is around integer times of the period of the metallic patterns. The mechanism of field amplification is similar to Fabry-Perot type resonance between two reflecting surfaces. The strong thermal electric field from resonance allows long-distance photon tunneling observed in near field radiation at a ~5 µm separation distance when the same metallic patterns are placed on the collector surfaces. This value is nearly 50 times longer than that with bared emitter surfaces. This long-distance photon tunneling can also happen at a broader range of parallel wavenumbers at the surface plasmon frequency when the periodic metallic patterns' sizes are different each period. However, increasing the range of parallel wavenumbers in long-distance photon tunneling with this approach can reduce the strength of photon tunneling. The reduced tunneling strength can be brought up by attaching high refractive index dielectric resonators on top of the metallic patterns through additional Mie-type resonance when displacement current is induced at the interface between the metallic patterns and the high refractive index dielectric.

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.…”

Analysis of near field radiation among lithography-free metal-dielectric-metal perfect absorbers with a combined numerical method

“…Based on the semi-analytical solution, spectral radiation flux q ′ ′ 1−2 (ω, T) from a semi-infinite domain 1 to a collector 2 through an intermediate region can be expressed as [4,5]…”

“…) can be considered as directional spectral emissivity in TM mode. F TE (k x , 0) and F TM (k x , 0) values can be determined with the RCWA method [4,[21][22][23][24].…”

“…Fewer near-field emitter/absorber configurations have been studied compared to far-field perfect light absorbers. Similar to far-field emitters/absorbers, the near-field emissivity of a surface and the associated photon tunneling distance can be significantly improved with optical resonances [4,5]. Thus, a farfield perfect absorber using optical resonance has the potential to be a near-field emitter/absorber, providing long-distance photon tunneling and strong near-field radiation.…”

“…With the integrated analysis, we then study the near-field radiations spectrum of recently demonstrated lithography-free metal-dielectric-metal (MIM) structures showing far-field broadband and wide-angle perfect light absorption [3,19,20]. The angular insensitive property is desired in near-field radiation, considering that most demonstrated long-distance photon tunneling structures show strong dispersion relations between the frequency and the parallel wavenumbers, preventing them from high-intensity quasi-monochromatic energy transport desired in many energy applications [4,5]. Suppose the material can have strong photon tunneling throughout all parallel wavenumbers for a specific wavelength.…”