Broadband near-field radiative thermal emitter/absorber based on hyperbolic metamaterials: Direct numerical simulation by the Wiener chaos expansion method

Baoan Liu,Sheng Shen

doi:10.1103/physrevb.87.115403

Abstract

In the near field, radiative heat transfer can exceed the prediction from Planck's law by several orders of magnitude, when the interacting materials support surface polaritons in the infrared range. However, if the emitter and absorber are made from two different materials, which support surface polariton resonances at different frequencies, the mismatch between surface polariton resonance frequencies will drastically reduce near-field radiative heat transfer. Here, we present a broadband near-field thermal emitter/absorber based on hyperbolic metamaterials, which can significantly enhance near-field radiative heat transfer with infrared surface-polariton-resonance materials and maintain the monochromatic characteristic of heat transfer. Instead of using an effective medium approximation, we perform a direct numerical simulation to accurately investigate the heat transfer mechanisms of metamaterials based on the Wiener chaos expansion method.

Highlights

In the near-field, when the gap distance between objects is smaller than the dominant thermal wavelength predicted by Wien’s displacement law, radiative heat transfer can be greatly enhanced by photon tunneling through evanescent electromagnetic waves[1,2,3]
We present a broadband non-resonant heat emitter/absorber based on hyperbolic metamaterials[17,18,19], which can significantly enhance near-field radiative heat transfer between metals and infrared surface-polariton resonances (IR-SPRs) thermal emitters, and maintain the monochromatic characteristic of the IR-SPR based near-field radiation
We described a hyperbolic metamaterial based heat emitter/absorber made of metal wire arrays (MWAs), which can greatly enhance near-field heat transfer with IR-SPR materials

Summary

Introduction

In the near-field, when the gap distance between objects is smaller than the dominant thermal wavelength predicted by Wien’s displacement law, radiative heat transfer can be greatly enhanced by photon tunneling through evanescent electromagnetic waves[1,2,3]. The IR-SPR based near-field heat transfer is dominated by the contribution from the TM waves that have a purely imaginary kz and a large surface wave vector K ( K > k0 )[1] These waves are evanescent in vacuum but can be converted into propagating waves by hyperbolic metamaterials for arbitrarily large K. Plot of the expression Im[rTM ]exp(−γ d ) to estimate the photon local density of state (LDOS) at d = 100nm above the surface of semi-infinite (a) SiC, (b) Au, and (c) limiting case of metal wire arrays (MWAs)

Wiener-chaos expansion method

Simulation results

10-11 Blackbody

Conclusion