Manipulating thermal emission with spatially static fluctuating fields in arbitrarily shaped epsilon-near-zero bodies

Abstract

The control and manipulation of thermal fields is a key scientific and technological challenge, usually addressed with nanophotonic structures with a carefully designed geometry. Here, we theoretically investigate a different strategy based on epsilon-near-zero (ENZ) media. We demonstrate that thermal emission from ENZ bodies is characterized by the excitation of spatially static fluctuating fields, which can be resonantly enhanced with the addition of dielectric particles. The "spatially static" character of these temporally dynamic fields leads to enhanced spatial coherence on the surface of the body, resulting in directive thermal emission. By contrast with other approaches, this property is intrinsic to ENZ media and it is not tied to its geometry. This point is illustrated with effects such as geometry-invariant resonant emission, beamforming by boundary deformation, and independence with respect to the position of internal particles. We numerically investigate a practical implementation based on a silicon carbide body containing a germanium rod.

Viscoelastic optical nonlocality of low-loss epsilon-near-zero nanofilms

“…The result is the enhancement of the normal electric-field component inside the film and the formation of an absorption peak in the spectrum 31 . Recently, a growing number of applications have been identified for ENZ materials, including structural color formation by metallic-network ENZ metamaterials 32 , enhanced absorption in thin-film photovoltaics 33 , record-efficient plasmonic photocatalysis for hydrogen production 34 , thermal radiation engineering 35 , and broadband perfect absorption in gap-plasmon metasurfaces 36 . So far, these phenomena have been discussed within the local approximation of the film’s dielectric constant, in which the relative permittivity depends only on the frequency, i.e., ε L (ω)= ε ′( ω ) + iε ′′( ω ).…”

Strong self-induced nonreciprocal transmission by using nonlinear PT-symmetric epsilon-near-zero metamaterials

“…2, where the linear transmission and reflection spectra of the proposed metamaterial are computed by using COMSOL Multiphysics, a commercial full-wave simulation software. The dispersion of the materials is neglected, since we focus our study only in a narrow wavelength range around The ENZ response in real materials, such as transparent conductive oxides (TCOs) and SiC, is not ideal (lossless) due to a moderate optical loss [17][18][19][20][21]. Figure 3 shows the backward reflectance Fig.…”

“…In the results shown in Fig. 5, SiC is used as the ENZ material with Im( ) 0.03 ENZ   at its mid-IR ENZ response [19][20][21]. The thickness of the ENZ media is decreased to coefficient  value is much larger compared to the lossless ENZ media but still in a practical feasible range [22,23].…”

“…where t A a b  is the total area of the ENZ and defect, The ENZ response in real materials, such as transparent conductive oxides (TCOs) and SiC, is not ideal (lossless) due to a moderate optical loss [17][18][19][20][21]. Figure 3 4.…”

Polaritonic hybrid-epsilon-near-zero modes: engineering strong optoelectronic coupling and dispersion in doped cadmium oxide bilayers

“…Such epsilon-near-zero (ENZ) phenomena occur near the frequency where the real part of the dielectric function changes sign and are characterized by electromagnetic modes with light wavelengths in the ENZ medium diverging toward infinity, along with decoupled spatial and temporal electromagnetic fields. [1] Harnessing this behavior has recently become a major objective in nanophotonics research; examples include resonant perfect light absorption in deeply sub-wavelength thin films, [2,3,4,5] length-invariant antenna resonances, [6] wave-front engineering, [7] controlled thermal emissivity, [8,9] and extraordinary transmission by supercoupling. [10] Practically, an ENZ condition can be realized in any material or system where the real part of the effective dielectric function passes through zero, and thus occurs naturally in materials such as doped semiconductors [3,5,11] and polar crystals.…”