He Tao, Liu Tong, Xiao Shiyi, Wei Zeyong, Wang Zhanshan, Zhou Lei, Cheng Xinbin
MOE Key Laboratory of Advanced Micro-Structured Materials, Shanghai 200092, China.
Institute of Precision Optical Engineering, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China.
Sci Adv. 2022 Mar 4;8(9):eabk3381. doi: 10.1126/sciadv.abk3381. Epub 2022 Mar 2.
Reflecting light to a predetermined nonspecular direction is an important ability of metasurfaces, which is the basis for a wide range of applications (e.g., beam steering/splitting and imaging). However, anomalous reflection with 100% efficiency has not been achieved at optical frequencies yet, because of losses and/or insufficient nonlocal control of light waves. Here, we propose an all-dielectric quasi-three-dimensional subwavelength structure, consisting of multilayer films and metagratings, to achieve perfect anomalous reflections at optical frequencies. A complex multiple scattering process was stimulated by effectively coupling different Bloch waves and propagating waves, thus offering the metasystem the desired nonlocal control on light waves required by perfect anomalous reflections. Two perfect anomalous reflectors were demonstrated to reflect normally incident 1550-nm light to the 40°/75° directions with absolute efficiencies of 99%/99% in design (98%/88% in experiment). Our results pave the way toward realizing optical metadevices with desired high efficiencies in realistic applications.
将光反射到预定的非镜面方向是超表面的一项重要能力，这是广泛应用（如光束转向/分裂和成像）的基础。然而，由于光波的损耗和/或非局部控制不足，尚未在光频实现100%效率的异常反射。在此，我们提出一种全介质准三维亚波长结构，由多层膜和超光栅组成，以在光频实现完美的异常反射。通过有效耦合不同的布洛赫波和传播波，激发了一个复杂的多重散射过程，从而为超系统提供了完美异常反射所需的对光波的非局部控制。实验证明，两个完美的异常反射器能够将垂直入射的1550纳米光反射到40°/75°方向，设计中的绝对效率为99%/99%（实验中为98%/88%）。我们的结果为在实际应用中实现具有所需高效率的光学超器件铺平了道路。
