A four-band terahertz tunable narrow-band perfect absorber based on a bulk Dirac semi-metallic (BDS) metamaterial with a microstructure is designed. The three-layer structure of this absorber from top to bottom is the Dirac semi-metallic layer, the dielectric layer and the metal reflector layer. Based on the Finite Element Method (FEM), we use the simulation software CST STUDIO SUITE to simulate the absorption characteristics of the designed absorber. The simulation results show that the absorption rate of the absorber is over 93% at frequencies of 1.22, 1.822, 2.148 and 2.476 THz, and three of them have achieved a perfect absorption rate of more than 95%. We use the localized surface plasmon resonance (LSPR), impedance matching and other theories to analyze its physical mechanism in detail. The influence of the geometric structure parameters of the absorber and the incident angle of electromagnetic waves on the absorption performance has also been studied in detail. Due to the rotational symmetry of the structure, the designed absorber has excellent polarization insensitivity. In addition, the maximum adjustable range of absorption frequency is 0.051 THz, which can be achieved by changing the Fermi energy of BDS. We also define the refractive index sensitivity (S), which is 39.1, 75.4, 119.1 and 122.0 GHz RIU⁻¹ for the four absorption modes when the refractive index varies in the range of 1 to 1.9. This high-performance absorber has a very good development prospect in the frontier fields of bio-chemical sensing and special environmental detection.

中文翻译：

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具有高折射率灵敏度的四波段和偏振无关的基于 BDS 的可调吸收器

设计了一种基于具有微观结构的块状狄拉克半金属 (BDS) 超材料的四波段太赫兹可调窄带完美吸收器。这种吸收体自上而下的三层结构是狄拉克半金属层、介电层和金属反射层。基于有限元法（FEM），我们使用仿真软件CST STUDIO SUITE对设计的吸收体的吸收特性进行仿真。仿真结果表明，该吸波器在1.22、1.822、2.148和2.476 THz频率下的吸收率均在93%以上，其中三种达到了95%以上的完美吸收率。我们利用局域表面等离子体共振（LSPR）、阻抗匹配等理论对其物理机制进行了详细分析。还详细研究了吸收体的几何结构参数和电磁波的入射角对吸收性能的影响。由于结构的旋转对称性，设计的吸收体具有优异的偏振不敏感性。此外，吸收频率的最大可调范围为0.051 THz，可以通过改变北斗系统的费米能量来实现。我们还定义了折射率敏感度（S )，当折射率在 1 到 1.9 的范围内变化时，四种吸收模式的RIU ^{-1 分别}为39.1、75.4、119.1 和 122.0 GHz 。这种高性能吸收体在生化传感和特殊环境检测等前沿领域具有很好的发展前景。