*Article* **High-Efficiency and Wide-Angle Versatile Polarization Controller Based on Metagratings**

**Kun Song 1,\*,†, Ruonan Ji 1,†, Duman Shrestha 2, Changlin Ding 1, Yahong Liu 1, Weiren Zhu 3, Wentao He 1, Huidong Liu 1, Yuhua Guo 1, Yongkang Tang 1, Xiaopeng Zhao 1,\* and Jiangfeng Zhou 2,\***


Received: 28 January 2019; Accepted: 15 February 2019; Published: 19 February 2019

**Abstract:** Metamaterials with their customized properties enable us to efficiently manipulate the polarization states of electromagnetic waves with flexible approaches, which is of grea<sup>t</sup> significance in various realms. However, most current metamaterial-based polarization controllers can only realize single function, which has extremely hindered the expansion of their applications. Here, we experimentally demonstrate highly efficient and multifunctional polarization conversion effects using metagrating by integrating single-structure metallic meta-atoms into the dielectric gratings. Benefiting from the combined advantages of the gratings and the metamaterials, the considered metagrating can operate in transmission and reflection modes simultaneously, acting as a high-performance and wide-angle quarter-wave or half-wave plate with distinct functions in different frequency bands. This metagrating structure is scalable to other frequency ranges and may provide opportunities to design compact multifunctional optical polarization control devices.

**Keywords:** metagratings; polarization controller; multifunction; wide-angle; dual mode
