An Ultra-Wideband Terahertz Metamaterial Absorber Based on the Fractal Structure
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An Ultra-Wideband Terahertz Metamaterial Absorber Based on the Fractal Structure Hou-Bing Liu 1 & Cai-Xing Hu 1 & Zi-Long Wang 1 & Hai-Feng Zhang 1,2
&
Hai-Ming Li 3
Received: 13 May 2020 / Accepted: 6 September 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract In this paper, we propose an ultra-wideband terahertz (THz) metamaterial absorber (MA) based on a fractal structure, and the main structure of the MA includes the upper metal patch, the bottom metal reflector, and a single dielectric substrate between the two. The surface metal patch is the gold designed by fractal and topology theory to constitute the basic resonant unit, and then the surface base resonant unit is reduced and amplified at different scales. By approaching the resonance frequencies of each other, MA with an operating range of 6.39 to 9.47 THz was obtained, and its relative bandwidth (RB) is 38.8%. The absorption bandwidth can be extended by adjusting the ratio between the four groups of resonators, and the dielectric height can be adjusted to improve the efficiency of the absorption spectrum. In addition to the discussion of the above influencing factors, we are also curious about the principle behind absorption. Therefore, the distribution of the electric field strength and magnetic field strength of the designed MA and the influence of the polarization angle and incidence angle on the absorption bandwidth are simulated. Keywords Fractal theory . Terahertz . Metamaterials . Ultra-wideband absorption
Introduction Electromagnetic (EM) metamaterials are an artificial structure material composed of sub-wavelength structure as a unit, which has some special properties [1, 2] that are not found in ordinary materials, for example, the negative refractive index [3, 4], negative dielectric constant, etc. According to the spectral range of electromagnetic metamaterials, we divide them into microwave metamaterials, terahertz metamaterials [5, 6], and optical metamaterials [7, 8]. Because of the peculiar physical properties of metamaterials, they have wide research value. In recent years, since Landy et al. [9] presented the first perfect absorber, perfect metamaterial absorbers [10–14] have been developed in microwave, THz [15, 16], infrared [17–19], * Hai-Feng Zhang [email protected] 1
College of Electronic and Optical Engineering & College of Microelectronics, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
2
State Key Laboratory of Millimeter Waves of Southeast University, Nanjing 210096, China
3
College of Telecommunications & Information Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210003, China
and visible wavelengths. The absorber has potential applications in THz imaging [20, 21], signal detection [22], dielectric thickness detection, and sensing. Part of the engineering design and production of metamaterial absorbent is to achieve a better absorption effect. However, most of these designs and applications have the same common disadvantage, that is, t
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