Omnidirectional, polarization-independent, ultra-broadband metamaterial perfect absorber using field-penetration and reflected-wave-cancellation

Abstract

In this work, we present the result of nickel (Ni)-based metamaterial perfect absorbers (MPA) with ultra-broadband close-to-one absorbance. The experimental broadband characteristic is significantly improved over the past effort on metamaterial perfect absorbers. An in-depth physical picture and quantitative analysis is presented to reveal the physical origin of its ultrabroadband nature. The key constituent is the cancellation of the reflected wave using ultra-thin, moderate-extinction metallic films. The ultra-thin metal thickness can reduce the reflection as the optical field penetrates through the metallic films. This leads to minimal reflection at each ultra-thin metal layer, and light is penetrating into the Ni/SiO₂ stacking. More intuitively, when the layer thickness is much smaller than the photon wavelength, the layer is essentially invisible to the photons. This results in absorption in the metal thin-film through penetration while there is minimal reflection by the metal film. More importantly, the experimental evidence for omni-directionality and polarization-insensitivity are established for the proposed design. Detailed measurement is conducted. Due to the ultrathin metal layers and the satisfactory tolerance in dielectric thickness, the broadband absorption has minimal degradation at oblique incidence. Such a wide angle, polarization-insensitive, ultra-broadband MPA can be very promising in the future, and the optical physics using sub-skin-depth metal film can also facilitate miniaturized high-performance nano-photonic devices.

97 percent light absorption in an ultrabroadband frequency range utilizing an ultrathin metal layer: randomly oriented, densely packed dielectric nanowires as an excellent light trapping scaffold

“…In a recent study, it was theoretically and experimentally demonstrated that the use of planar unpatterned metal-insulator (MI) pairs can provide an ultra-broadband light absorption where the absorption bandwidth can extend to longer wavelengths by adding up the number of pairs. 40 After the study, a wide variety of MI combinations including W-Al 2 O 3 , 41 Cr-SiO 2 , 42 Ag-Si, 43 and Ni-SiO 2 44 were later utilized to improve the absorption capability of this architecture. A substantial enhancement in the light absorption capacity of these MI multilayer designs was achieved by the introduction of tapered configuration.…”

Strong Interference in Planar, Multilayer Perfect Absorbers: Achieving High-Operational Performances in Visible and Near-Infrared Regimes

“…However, these modifications do not adequately improve the absorption upper edge. Even using a larger number of [MI] N pairs (e.g., 16 pairs) cannot significantly substantiate the BW [32]. In a recent article, our group revealed an extraordinary optical response of bismuth (Bi) metal in lightperfect absorption [46].…”

Semiconductor Thin Film Based Metasurfaces and Metamaterials for Photovoltaic and Photoelectrochemical Water Splitting Applications

“…Different metal–insulator combinations were utilized to obtain ultrabroadband light absorption from these multilayer designs. W‐Al 2 O 3 , Cr‐SiO 2 , W‐SiO 2 , Mo‐SiO 2 , Ag‐Si, Bi‐LiF, and Ni‐SiO 2 are some examples of these MI pairs to obtain perfect broadband absorption. Further improvements can be also achieved using different strategies; excitation of multiple modes in a multithickness absorbing layer, reducing the effective permittivity of metals via their composition with air, the optimal selection of materials to maximize absorption BW are some examples of these strategies.…”