Abstract-Broadband diffusion of terahertz waves by multi-bit coding metasurfaces

Li-Hua Gao¹, Qiang Cheng^1,2, Jing Yang³, Shao-Jie Ma⁴, Jie Zhao¹, Shuo Liu¹, Hai-Bing Chen¹, Qiong He⁴, Wei-Xiang Jiang^1,2, Hui-Feng Ma^1,2, Qi-Ye Wen^2,5, Lan-Ju Liang^6,7, Biao-Bing Jin^2,6, Wei-Wei Liu^2,3, Lei Zhou⁴, Jian-Quan Yao⁷, Pei-Heng Wu⁶ and Tie-Jun Cui^1,2

1. ¹State Key Laboratory of Millimeter Waves, Department of Radio Engineering, Southeast University, Nanjing 210096, China
2. ²Cooperative Innovation Centre of Terahertz Science, No. 4, Section 2, North Jianshe Road, Chengdu 610054, China
3. ³Institute of Modern Optics, Key Laboratory of Optical Information Science and Technology (Ministry of Education), Nankai University, Tianjin 300071, China
4. ⁴State Key Laboratory of Surface Physics, Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Department of Physics, Fudan University, Shanghai 200433, China
5. ⁵State Key Laboratory of Electronic Films and Integrated Devices, University of Electronic Science and Technology, Chengdu 610054, China
6. ⁶Research Institute of Superconductor Electronics (RISE), School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, China
7. ⁷Institute of Lasers and Optoelectronics, College of Precision Instrument and Opto-Electronics Engineering, Tianjin University, Tianjin 300072, China

Correspondence: Q Cheng, Email: qiangcheng@seu.edu.cn; TJ Cui, Email: tjcui@seu.edu.cn

Received 16 January 2015; Revised 23 April 2015; Accepted 26 April 2015

http://www.nature.com/lsa/journal/v4/n9/full/lsa201597a.html

The terahertz region is a special region of the electromagnetic spectrum that incorporates the advantages of both microwaves and infrared light waves. In the past decade, metamaterials with effective medium parameters or gradient phases have been studied to control terahertz waves and realize functional devices. Here, we present a new approach to manipulate terahertz waves by using coding metasurfaces that are composed of digital coding elements. We propose a general coding unit based on a Minkowski closed-loop particle that is capable of generating 1-bit coding (with two phase states of 0 and 180°), 2-bit coding (with four phase states of 0, 90°, 180°, and 270°), and multi-bit coding elements in the terahertz frequencies by using different geometric scales. We show that multi-bit coding metasurfaces have strong abilities to control terahertz waves by designing-specific coding sequences. As an application, we demonstrate a new scattering strategy of terahertz waves—broadband and wide-angle diffusion—using a 2-bit coding metasurface with a special coding design and verify it by both numerical simulations and experiments. The presented method opens a new route to reducing the scattering of terahertz waves.