Role of nanoparticles in wavelength selectivity of multilayered structures in the far-field and near-field regimes

Abstract

Microscopic thin films have shown wavelength selectivity in the context of radiative heat transfer. We propose a methodology to shift the wavelength selectivity in the desired location. This work deals with the far-field and near-field radiation from thin films embedded with nanoparticles. The calculations of emission spectra are performed using the Fresnel equations in the far-field limit, and using the dyadic Green's function formalism for transmissivity between the closely spaced objects in the near-field regime. For the media doped with nanoparticles, an effective dielectric function using the Maxwell-Garnett-Mie theory is used to calculate emissivity and radiative heat transfer. It has been shown that the wavelength selectivity in the emission spectra can be influenced by varying the size and/or the volume fraction of nanoparticles. We characterize the wavelength selectivity using real and imaginary parts of the effective refractive index. We show that the influence of nanoparticles on wavelength selectivity is different depending on whether the particles are of polar materials or are metallic.

Photonic Metamaterials: Controlling Nanoscale Radiative Thermal Transport

“…where Θω ; T ðÞ ¼ ℏω=2 ðÞ coth ℏω=2k B T ðÞ is the energy of harmonic oscillator at frequency ω and temperature T, ℏ is the reduced Planck constant, and k B is the Boltzmann constant. The function T 1!2 ω; L ðÞ is known as the spectral transmissivity in radiative transfer between media 1 and 2 separated of distance L [26,32,36,55] and is expressed as…”

“…is ignored as separation between the two half spaces is much larger than the thermal wavelength L ≫ λ th ðÞ . The hemispherical emissivity of the active component can be expressed as [32] e ω ðÞ ¼…”

“…Spectral control has been studied to affect radiative heat transfer in both the far-field as well as near-field. Customization of absorption/emission spectra is often achieved by the use of multilayer thin film structures [29], nanoparticles [30,31], dielectric mixtures [32,33], photonic crystals [34,35], 1-D/2-D gratings [36] and metamaterials [37,38]. Absorbers that utilize Fabry-Perot cavities [39,40], Salisbury screens [41] and Jaumann absorbers [42] and ultra-thin lossy thin films bounded by transparent substrate and superstate [43][44][45] have been investigated for decades.…”

High Contrast Far-Field Radiative Thermal Diode

“…The terms due to evanescent waves are ignored as separation between the two half spaces is much larger than the thermal wavelength (). The hemispherical emissivity of the active component can be expressed as 32 …”

“…Customization of absorption/emission spectra is often achieved by the use of multilayer thin film structures 29 , nanoparticles 30, 31 , dielectric mixtures 32, 33 , photonic crystals 34, 35 , 1-D/2-D gratings 36 and metamaterials 37, 38 . Absorbers that utilize Fabry-Perot cavities 39, 40 , Salibury screens 41 and Jaumann absorbers 42 and ultra-thin lossy thin films bounded by transparent substrate and superstate 43–45 have been investigated for decades.…”