Conventional gradient metasurface suffers from low efficiency because of impedance mismatching, especially in large-angle manipulation. Here we propose an asymmetric sandwich-like material element to design bianisotropic metasurface for full-angle high-efficiency anomalous refractive manipulation. The proposed asymmetric element is composed of two different auxiliary layers attached to the core layer which can be viewed as a conventional gradient index metasurface, and we demonstrate analytically that these sandwich-like structures can exhibit a bianisotropic response and meet the normal impedance matching condition at both sides of the metasurface. Besides, this material design concept can be realized via the space-coiling structures. The availability of the element is first demonstrated by a nearly total refraction at an extreme refracted angle (up to 80). Subsequently, these elements are used for the transition connection of different waveguides and dramatically improve the transmission performance. Our method brings new possibilities for the design and application of bianisotropic metasurfaces.

由于阻抗不匹配，传统的梯度超表面效率低下，尤其是在大角度操作中。在这里，我们提出了一种不对称的三明治状材料元素来设计双各向异性超表面，用于全角高效异常折射操纵。所提出的非对称元件由连接到核心层的两个不同的辅助层组成，可以将其视为传统的梯度指数超表面，我们通过分析证明这些三明治状结构可以表现出双各向异性响应并满足正常阻抗匹配条件超曲面的两侧。此外，这种材料设计理念可以通过空间盘绕结构来实现。该元件的可用性首先通过极端折射角（高达 80 度）处的近乎全折射来证明。随后，这些元件用于不同波导的过渡连接，并显着提高传输性能。我们的方法为双各向异性超表面的设计和应用带来了新的可能性。