Complex non-local behavior makes designing high efficiency and multifunctional metasurfaces a significant challenge. While using libraries of meta-atoms provide a simple and fast implementation methodology, pillar to pillar interaction often imposes performance limitations. On the other extreme, inverse design based on topology optimization leverages non-local coupling to achieve high efficiency, but leads to complex and difficult to fabricate structures. In this paper, we demonstrate numerically and experimentally a shape optimization method that enables high efficiency metasurfaces while providing direct control of the structure complexity through a Fourier decomposition of the surface gradient. The proposed method provides a path towards manufacturability of inverse-designed high efficiency metasurfaces.

复杂的非局部行为使设计高效和多功能的超表面成为一项重大挑战。虽然使用元原子库提供了一种简单快速的实现方法，但 pillar 到 pillar 的交互通常会带来性能限制。在另一个极端，基于拓扑优化的逆向设计利用非局部耦合来实现高效率，但会导致结构复杂且难以制造。在本文中，我们通过数值和实验展示了一种形状优化方法，该方法可实现高效的超表面，同时通过表面梯度的傅里叶分解直接控制结构复杂性。所提出的方法为逆向设计的高效超表面的可制造性提供了一条途径。