School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore, 639798, Singapore.
School of Optoelectronic Science and Engineering, University of Electronic Science and Technology, Chengdu, 610051, China.
Adv Mater. 2018 Sep;30(39):e1802721. doi: 10.1002/adma.201802721. Epub 2018 Aug 20.
The metasurface concept is employed to planarize retroflectors by stacking two metasurfaces with separation that is two orders larger than the wavelength. Here, a retroreflective metasurface using subwavelength-thick reconfigurable C-shaped resonators (RCRs) is reported, which reduces the overall thickness from the previous record of 590 λ down to only 0.2 λ . The geometry of RCRs could be in situ controlled to realize equal amplitude and phase modulation onto transverse magnetic (TM)-polarized and transverse electric (TE)-polarized incidences. With the phase gradient being engineered, an in-plane momentum could be imparted to the incident wave, guaranteeing the spin state of the retro-reflected wave identical to that of the incident light. Such spin-locked metasurface is natively adaptive toward different incident angles to realize retroreflection by mechanically altering the geometry of RCRs. As a proof of concept, an ultrathin retroreflective metasurface is validated at 15 GHz, under various illumination angles at 10°, 12°, 15°, and 20°. Such adaptive spin-locked metasurface could find promising applications in spin-based optical devices, communication systems, remote sensing, RCS enhancement, and so on.
该超构表面采用亚波长厚度的可重构 C 型谐振器（RCR），将整体厚度从之前的 590λ 缩减至仅 0.2λ。通过对 RCR 的几何形状进行原位控制，可实现对 TM 偏振和 TE 偏振入射光的等幅和相位调制。通过设计相位梯度，可向入射波赋予面内动量，从而保证反射波的自旋状态与入射光相同。这种自旋锁定超构表面具有固有适应性，可通过机械改变 RCR 的几何形状来实现不同入射角的反向反射。作为概念验证，在 10°、12°、15°和 20°的各种照明角度下，在 15GHz 下验证了这种超薄反向反射超构表面。这种自适应的自旋锁定超构表面在基于自旋的光学器件、通信系统、遥感、RCS 增强等领域具有广阔的应用前景。
