1,990 research outputs found
Ultra-wideband THz/IR Metamaterial Absorber based on Doped Silicon
Metamaterial-based absorbers have been extensively investigated in the
terahertz (THz) range with ever increasing performances. In this paper, we
propose an all-dielectric THz absorber based on doped silicon. The unit cell
consists of a silicon cross resonator with an internal cross-shaped air cavity.
Numerical results suggest that the proposed absorber can operate from THz to
mid-infrared, having an average power absorption of >95% between 0.6 and 10
THz. Experimental results using THz time-domain spectroscopy show a good
agreement with simulations. The underlying mechanisms for broadband absorptions
are attributed to the combined effects of multiple cavities modes formed by
silicon resonators and bulk absorption in the substrate, as confirmed by
simulated field patterns. This ultra-wideband absorption is polarization
insensitive and can operate across a wide range of the incident angle. The
proposed absorber can be readily integrated into silicon-based platforms and is
expected to be used in sensing, imaging, energy harvesting and wireless
communications systems.Comment: 6 pages, 5 figure
Full light absorption in single arrays of spherical nanoparticles
In this paper we show that arrays of core-shell nanoparticles function as
effective thin absorbers of light. In contrast to known metamaterial absorbers,
the introduced absorbers are formed by single planar arrays of spherical
inclusions and enable full absorption of light incident on either or both sides
of the array. We demonstrate possibilities for realizing different kinds of
symmetric absorbers, including resonant, ultra-broadband, angularly selective,
and all-angle absorbers. The physical principle behind these designs is
explained considering balanced electric and magnetic responses of unit cells.
Photovoltaic devices and thermal emitters are the two most important potential
applications of the proposed designs.Comment: (e.g.: 18 pages, 5 figures
Noble-metal-free sunlight harvesting meta-surface for water evaporation
We present ultrathin multilayer metamaterial absorbers based on abundant, low-cost materials, to effectively harness solar energy for heating and evaporation of water
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Advances and challenges in commercializing radiative cooling
Radiative cooling (RC) dissipates terrestrial heat to outer space through the atmospheric window, without external energy input and production of environmental pollutants. More and more efforts have been devoted to this clean promising cooling technology; thus diverse radiative coolers have emerged. However, the performance, cost, and effectiveness of various radiative coolers are not exactly the same. In addition, the large-scale application of RC technology is impeded by the low energy density, uncontrollable cooling power, and limited sky-facing area. Here, we critically review the recent progress of RC technology, evaluate the cooling performance of various radiative coolers, and discuss the challenges and feasible solutions to commercialize RC technology. Furthermore, valuable insights are provided to make new breakthroughs in this field
Wavevector Selective Metasurfaces and Tunnel Vision Filters
Metasurfaces offer unprecedented flexibility in the design and control of
light propagation, replacing bulk optical components and exhibiting exotic
optical effects. One of the basic properties of the metasurfaces, which renders
them as frequency selective surfaces, is the ability to transmit or reflect
radiation within a narrow spectral band that can be engineered on demand. Here
we introduce and demonstrate experimentally in the THz domain the concept of
wavevector selective surfaces -- metasurfaces transparent only within a narrow
range of light propagation directions operating effectively as tunnel vision
filters. Practical implementations of the new concept include applications in
wavefront manipulation, observational instruments, vision and free-space
communication in light-scattering environments, as well as passive camouflage
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