In this work we present a new mechanism for designing phase-gradient metasurfaces (PGMs) to control an electromagnetic wavefront with high efficiency. Specifically, we design a transmission-type PGM formed by a periodic subwavelength metallic slit array filled with identical dielectrics of different heights. It is found that when Fabry-Perot (FP) resonances occur locally inside the dielectric regions, in addition to the common phenomenon of complete transmission, the transmitted phase differences between two adjacent slits are exactly the same, being a non-zero constant. These local FP resonances ensure total phase shift across a supercell that can fully cover the range of 0 to 2Pi, satisfying the design requirements of PGMs. More studies reveal that due to local FP resonances, there is a one-to-one correspondence between the phase difference and the permittivity of the filled dielectric. A similar approach can be extended to the reflection-type case and other wavefront transformation, creating new opportunities for wave manipulation.

中文翻译：

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基于局部法布里-珀罗共振的相位梯度超表面

在这项工作中，我们提出了一种设计相位梯度超表面（PGM）以高效控制电磁波前的新机制。具体而言，我们设计了一种透射型 PGM，由填充有不同高度的相同电介质的周期性亚波长金属狭缝阵列形成。发现当法布里-珀罗(FP)谐振在介电区域内局部发生时，除了完全透射的常见现象外，两个相邻狭缝之间的透射相位差完全相同，为非零常数。这些局部 FP 共振确保整个超级单元的总相移可以完全覆盖 0 到 2Pi 的范围，满足 PGM 的设计要求。更多的研究表明，由于局部 FP 共振，相位差与填充电介质的介电常数之间存在一一对应的关系。类似的方法可以扩展到反射型情况和其他波前变换，为波操纵创造新的机会。