Ultrawideband Terahertz Absorption Induced by Pyramidal 3-D Metamaterial

The planar hybrid metallic microstructured metamaterials can utilize the transverse electromagnetic resonance coupling effect of adjacent resonant units to enhance the absorption bandwidth (ABW), which is widely used in the design of broadband terahertz (THz) absorbers. However, it is difficult to further broaden the ABW since only a limited number of resonant units can be arranged in the 2-D plane. Here, we propose a pyramidal 3-D metamaterial absorber that increases the number of resonances by superimposing metallic dielectric layers with different sizes in the vertical direction. Ultrawideband wave absorption at THz frequencies is realized by longitudinal electromagnetic resonance coupling between the layers of the metamaterial structure. The results show that the 3-D metamaterial achieves more than 90% ultrabroadband absorption in the range of 0.83-2.73 THz with the relative ABW exceeding 106%. In addition, the equivalent circuit model of the absorber is constructed to verify the simulation results. This study provides a novel idea for the design and processing of ultrawideband THz absorbers.