An Ultra-Wideband Terahertz Metamaterial Absorber Based on the Fractal Structure

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.