Numerical Study of an Ultra-Broadband and Polarization Independence Metamaterial Cross-Shaped Fractal Absorber
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Numerical Study of an Ultra-Broadband and Polarization Independence Metamaterial Cross-Shaped Fractal Absorber Juefu Liu 1 & Jiao Chen 1 & Huan Liu 1 & Yuanyuan Liu 1 & Lu Zhu 1 Received: 18 October 2019 / Accepted: 22 March 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract A three-dimensional cross-shaped fractal metamaterial absorber with ultra-wide wavelength band, polarization-independence and wide-angle, is numerically investigated by the finite-difference time-domain method. In this absorber, the solar energy is trapped by the cross-shaped fractal of the upper layer, and the Si-ring filled with iron in the middle layer and the wavelength band can be broadened by the self-similarity of fractal structure. The absorber exhibits absorptivity higher than 91% for the wavelengths from 400 to 2000 nm and an absorption bandwidth of about 133%. Furthermore, the proposed absorber realizes polarization independence, and the maximum incident angle is 76°. However, as the iron material applied in the nanometamaterial absorber (NMA) can be easily oxidized and rusted, it is replaced by nickel with characteristics such as corrosion resistance and high-temperature resistance; thus, an improved NMA is obtained. The improved absorber not only eliminates the corrosion-prone defects of the above proposed structure but also maintains polarization independence and high absorption and widens the angle of incidence up to 79° and thereby can be applied in many areas, such as solar energy harvesting. Keywords Metamaterial absorber . Fractal . Polarization independence . Ultra-broadband
Introduction Metamaterials, known as artificial composite electromagnetic material, have gained significant attention and extensive applications because of their unique electromagnetic properties. Metamaterial structures composed of periodic metallic and dielectric structures have been shown to couple with either electric or magnetic field to generate electric or magnetic resonant response based on the Drude model [1–3]. Absorbers based on metamaterial have been studied for various applications, such as sensors [4, 5], filters [6, 7], and solar energy cells [8–10]. In general, the high absorption of the absorber is attributed to the surface plasmon resonance of the nano-structures. However, their perfect absorption is confined to narrow bandwidths [11–13], which limits their practical application range. Therefore, some researchers have conducted detailed research on enhancing the bandwidths of metamaterial absorbers [14]. At present, common methods for broadening the bandwidths
* Jiao Chen [email protected] 1
College of Information Engineering, East China Jiaotong University, Nanchang 330013, China
mainly focus on combining structures with perfect absorption characteristics, stacking of lattice constants, or non-equal lattice constants of metal layers and dielectric layers [14–18]. DT Viet et al. investigated the absorption in a sandwich model of absorber metamaterial which consists of periodic metallic dishes at the
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