Xu Mingfeng, He Qiong, Pu Mingbo, Zhang Fei, Li Ling, Sang Di, Guo Yinghui, Zhang Renyan, Li Xiong, Ma Xiaoliang, Luo Xiangang
State Key Laboratory of Optical Technologies on Nano-Fabrication and Micro-Engineering, Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu, 610209, China.
Division of Frontier Science and Technology, Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu, 610209, China.
Adv Mater. 2022 Mar;34(12):e2108709. doi: 10.1002/adma.202108709. Epub 2022 Feb 7.
Recently, disordered metasurfaces have attracted considerable interest due to their potential applications in imaging, holography, and wavefront shaping. However, how to emerge long-range ordered phase distribution in disordered metasurfaces remains an outstanding problem. Here, a general framework is proposed to generate a spatially homogeneous in-plane phase distribution from a disordered metasurface, by engineering disorder parameters together with topology optimization. As a proof-of-concept demonstration, an all-dielectric disordered supercell metasurface with relatively homogeneous in-plane phase fluctuation is designed by disorder parameter engineering, manifesting as polarization conversion-dependent random scattering or unidirectional transmission. Then, a topology optimization approach is utilized to overcome the lattice coupling effect and to further improve the homogeneity of complex electric field fluctuation. In comparison with the initial supercell metasurface, both the phase fluctuation range and the relative efficiency of the topology-optimized freeform metasurface are significantly improved, leading to a long-range ordered electric field distribution. Moreover, three experimental realizations are performed, all of which agree well with the theoretical results. This methodology may inspire more exotic optical phenomena and find more promising applications in disordered metasurfaces and disordered optics.
近年来，无序超表面因其在成像、全息术和波前整形方面的潜在应用而备受关注。然而，如何在无序超表面中实现长程有序的相位分布仍然是一个突出的问题。在此，提出了一个通用框架，通过设计无序参数并结合拓扑优化，从无序超表面生成空间均匀的面内相位分布。作为概念验证演示，通过无序参数工程设计了一种具有相对均匀面内相位波动的全介质无序超胞超表面，表现为与偏振转换相关的随机散射或单向传输。然后，利用拓扑优化方法克服晶格耦合效应，并进一步提高复电场波动的均匀性。与初始超胞超表面相比，拓扑优化后的自由形式超表面的相位波动范围和相对效率均得到显著改善，从而实现了长程有序的电场分布。此外，进行了三个实验验证，所有结果均与理论结果吻合良好。该方法可能会激发更多奇异的光学现象，并在无序超表面和无序光学中找到更有前景的应用。
