Metasurfaces are two-dimensional arrangements of subwavelength scatterers that control the propagation of optical waves^1,2,3. Here, we show that cascaded metasurfaces, each performing a predefined mathematical transformation⁴, provide a new optical design framework⁵ that enables new functionalities not yet demonstrated with single metasurfaces. Specifically, we demonstrate that retroreflection can be achieved with two vertically stacked planar metasurfaces, the first performing a spatial Fourier transform and its inverse, and the second imparting a spatially varying momentum to the Fourier transform of the incident light. Using this concept, we fabricate and test a planar monolithic near-infrared retroreflector composed of two layers of silicon nanoposts, which reflects light along its incident direction with a normal incidence efficiency of 78% and a large half-power field of view of 60°. The metasurface retroreflector demonstrates the potential of cascaded metasurfaces for implementing novel high-performance components, and enables low-power and low-weight passive optical transmitters^6,7,8.

超表面是控制光波^1,2,3传播的亚波长散射体的二维排列。在这里，我们显示了级联的超表面，每个超表面执行了预定义的数学变换⁴，从而提供了新的光学设计框架⁵可以实现尚未通过单个超颖表面展示的新功能。具体而言，我们证明了可以使用两个垂直堆叠的平面形表面实现回射，第一个执行空间傅里叶变换及其逆变换，第二个将空间变化的动量赋予入射光的傅里叶变换。使用这一概念，我们制造并测试了由两层硅纳米柱组成的平面单片近红外逆向反射器，该反射器沿入射方向反射光，法向入射效率为78％，半功率视野为60° 。超表面后向反射器展示了级联超表面实现新的高性能组件的潜力，并实现了低功耗和低重量的无源光发射器^6,7,8。