Metasurfaces substituted for naturally occurring materials make it possible to develop flat optics manipulating terahertz waves. However, the control of unprecedented material properties with metasurfaces frequently produces anisotropic material properties and has yet to be commonly adopted because of the limitation of functionalities as optical components. Here, we demonstrate an isotropic metasurface with polarization-independent material properties with the extremely high refractive index of 14.0 + j0.49, low reflectance of 1.0 %, and high transmittance of 86.9 % at 0.31 THz. Measurements by terahertz time-domain spectroscopy (THz-TDS) verify that the fabricated metasurface with a high refractive index, low reflectance, and high transmittance works for terahertz waves with any polarization direction and results in the unprecedented material characteristics with polarization independence. The relative permittivity and relative permeability are 13.9 – j1.4 and 13.8 + j2.3, respectively. The sum of the dielectric and magnetic energy losses must also be considered to verify the conservation of energy for metasurfaces. The sum of the dielectric and magnetic energy losses is very close to positive values and the conservation of energy is largely satisfied. The proposed metasurface would offer optical components with attractive functionalities such as wavefront control, directivity enhancement, and optical vortices for 6G communications.

中文翻译：

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与偏振无关的各向同性超表面，在 0.3-THz 波段具有高折射率、低反射率和高透射率

用超表面代替天然存在的材料，可以开发出操纵太赫兹波的平面光学器件。然而，超表面对前所未有的材料特性的控制经常产生各向异性的材料特性，并且由于作为光学元件的功能的限制而尚未被普遍采用。在这里，我们展示了一个各向同性的超曲面，它具有与偏振无关的材料特性，具有 14.0 + 的极高折射率j0.49，1.0% 的低反射率，0.31 THz 时的 86.9% 的高透射率。太赫兹时域光谱 (THz-TDS) 的测量证实，所制造的具有高折射率、低反射率和高透射率的超表面适用于任何偏振方向的太赫兹波，并产生前所未有的偏振独立材料特性。相对介电常数和相对磁导率为 13.9 –j1.4 和 13.8 +j2.3，分别。还必须考虑介电和磁能损失的总和，以验证超表面的能量守恒。介电和磁能损失的总和非常接近正值，能量守恒基本得到满足。拟议的超表面将提供具有吸引人功能的光学元件，例如波前控制、方向性增强和用于 6G 通信的光学涡流。