Graded metasurfaces exploit the local momentum imparted by an impedance gradient to mold the impinging wave front. This approach suffers from fundamental limits on the overall conversion efficiency, and it is challenged by fabrication limitations on the spatial resolution. Here, we introduce the concept of metagratings, formed by periodic arrays of carefully tailored bianisotropic inclusions and show that they enable wave front engineering with unitary efficiency and significantly lower fabrication demands. We employ this concept to design reflective metasurfaces for wave front steering without limitations on efficiency. A similar approach can be extended to transmitted beams and arbitrary wave front transformation, opening opportunities for highly efficient metasurfaces for extreme wave manipulation.

中文翻译：

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迁移：超越波前控制的渐变超颖表面的极限

渐变的超表面利用阻抗梯度赋予的局部动量来塑造入射波阵面。这种方法受整体转换效率的基本限制，并且受到空间分辨率的制造限制的挑战。在这里，我们介绍由精心设计的各向异性夹杂物的周期性阵列形成的迁移概念，并表明它们使波前工程具有统一的效率并大大降低了制造需求。我们采用此概念来设计反射超表面，以进行波前转向，而不会影响效率。可以将类似方法扩展到透射光束和任意波阵面变换，从而为进行极端波操纵的高效超颖表面提供了机会。