Controlling thermal emission with refractory epsilon-near-zero metamaterials via topological transitions

Abstract

Control of thermal radiation at high temperatures is vital for waste heat recovery and for high-efficiency thermophotovoltaic (TPV) conversion. Previously, structural resonances utilizing gratings, thin film resonances, metasurfaces and photonic crystals were used to spectrally control thermal emission, often requiring lithographic structuring of the surface and causing significant angle dependence. In contrast, here, we demonstrate a refractory W-HfO2 metamaterial, which controls thermal emission through an engineered dielectric response function. The epsilon-near-zero frequency of a metamaterial and the connected optical topological transition (OTT) are adjusted to selectively enhance and suppress the thermal emission in the near-infrared spectrum, crucial for improved TPV efficiency. The near-omnidirectional and spectrally selective emitter is obtained as the emission changes due to material properties and not due to resonances or interference effects, marking a paradigm shift in thermal engineering approaches. We experimentally demonstrate the OTT in a thermally stable metamaterial at high temperatures of 1,000 °C.

Numerical study of a wide-angle polarization-independent ultra-broadband efficient selective metamaterial absorber for near-ideal solar thermal energy conversion

“…[27][28][29][30][31][32][33][34] However, as shown in Fig. 3(c), it is interesting to note that, the HMM waveguide arrays depicted in Fig.…”

“…In this work, W and SiO 2 are chosen as the base materials of the solar absorber owing to their thermal stability at high temperatures. 28,39 The nanopores of the structure are to reduce the effective refractive index of this absorber, which can achieve a better impedance match to free space. The rst SiO 2 layer coated onto the structure is operating as an antireective material, which is to further reduce the impedance mismatch.…”

“…Clearly, in this work, the HMM waveguide arrays, with electric eld along direction parallel to metal/dielectric waveguide, play a major role in the absorption enhancement of the original proposed absorber. Therefore, compared with the conventional tapered HMM (or sawtooth anisotropic metamaterial) absorbers, [27][28][29][30][31][32][33][34] which is related to the slow-light effect, our nanoporous HMM structures may have a completely different absorption mechanism.…”

Dynamic Thermal Emission Control Based on Ultrathin Plasmonic Metamaterials Including Phase‐Changing Material GST

“…The ability to control thermal emission contributes to a wide range of applications including radiative cooling, thermophotovoltaics, and adaptive camouflage . Plasmonic nanostructures have unique potentials in the control of thermal emission.…”

Tunable wideband-directive thermal emission from SiC surface using bundled graphene sheets

“…Precise control of its electromagnetic properties is challenging but highly aspired in many research and industrial applications such as solar energy harvesting [1][2][3] , thermophotovoltaics [4][5][6] , midinfrared incandescent light emitters [7][8][9] , spectroscopy 10 , and imaging 11 . Over the past decades, extreme control over spectral selectivity 8,[12][13][14][15][16][17][18][19][20] , emissivity [21][22][23][24] , and directionality [25][26][27][28][29][30][31] of thermal radiation have been achieved using micro and nano structures on top of hot surfaces 32 . For example, one-dimensional 18,33,34 and twodimensional photonic crystals 35 , nano-scale gaps [36][37][38] , hyperbolic metamaterials 37 , and polar materials with surface phonon polariton (SPhP) resonance 24,26,39,40 have been utilized to manipulate one or more electromagnetic properties of thermal radiation from a hot surface simultaneously …”