Abstract-Anisotropic coding metamaterials and their powerful manipulation of differently polarized terahertz waves

Shuo Liu^1,2,*, Tie Jun Cui^1,3,*, Quan Xu⁴, Di Bao^1,2, Liangliang Du⁴, Xiang Wan^1,2, Wen Xuan Tang^1,2, Chunmei Ouyang⁴, Xiao Yang Zhou^1,2,5, Hao Yuan⁵, Hui Feng Ma^1,2, Wei Xiang Jiang^1,2, Jiaguang Han⁴, Weili Zhang^3,4 and Qiang Cheng^1,3

1. ¹State Key Laboratory of Millimeter Waves, Southeast University, Nanjing 210096, China
2. ²Synergetic Innovation Center of Wireless Communication Technology, Southeast University, Nanjing 210096, China
3. ³Cooperative Innovation Centre of Terahertz Science, Chengdu 610054, China
4. ⁴Center for Terahertz Waves and College of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin 300072, China
5. ⁵Jiangsu Xuantu Technology Co., Ltd., Nanjing 211111, China

Correspondence: TJ Cui, Email: tjcui@seu.edu.cn

^*These authors contributed equally to this work.

Received 29 September 2015; Revised 19 January 2016; Accepted 20 January 2016
Accepted article preview online 26 January 2016

http://www.nature.com/lsa/journal/v5/n5/full/lsa201676a.html

Metamaterials based on effective media can be used to produce a number of unusual physical properties (for example, negative refraction and invisibility cloaking) because they can be tailored with effective medium parameters that do not occur in nature. Recently, the use of coding metamaterials has been suggested for the control of electromagnetic waves through the design of coding sequences using digital elements ‘0’ and ‘1,' which possess opposite phase responses. Here we propose the concept of an anisotropic coding metamaterial in which the coding behaviors in different directions are dependent on the polarization status of the electromagnetic waves. We experimentally demonstrate an ultrathin and flexible polarization-controlled anisotropic coding metasurface that functions in the terahertz regime using specially designed coding elements. By encoding the elements with elaborately designed coding sequences (both 1-bit and 2-bit sequences), the x- and y-polarized waves can be anomalously reflected or independently diffused in three dimensions. The simulated far-field scattering patterns and near-field distributions are presented to illustrate the dual-functional performance of the encoded metasurface, and the results are consistent with the measured results. We further demonstrate the ability of the anisotropic coding metasurfaces to generate a beam splitter and realize simultaneous anomalous reflections and polarization conversions, thus providing powerful control of differently polarized electromagnetic waves. The proposed method enables versatile beam behaviors under orthogonal polarizations using a single metasurface and has the potential for use in the development of interesting terahertz devices.

Terahertz Imaging System Uses BWO As Source

http://mwrf.com/test-amp-measurement/terahertz-imaging-system-uses-bwo-source

An imaging system based on transmission and reflection modes in the terahertz region has been developed by using a backward-wave oscillator (BWO) as its source, a Golay-Cell as the detector, and an oscilloscope as a data acquisition unit.

Much research has shown that terahertz waves can penetrate a number of materials while generating images with high spatial resolution. A number of these terahertz imaging solutions rely on continuous-wave radiation sources like a backward-wave oscillator (BWO). BWOs offer high output power, good wave-front quality, working-wavelength tunability, and a high signal-to-noise ratio. At China’s Southeast University, a continuous-wave (CW) terahertz imaging system using a BWO as source, a Golay-Cell as a detector, and an oscilloscope as a data-acquisition unit has been developed by Gang Chen, Jie Pei, Fei Yang, Xiao Yang Zhou, Z.L. Sun, and Tie Jun Cui.

The system’s software, which is based on the oscilloscope, is designed to control object movement as well as the capture and display of continuous terahertz-wave image data. To show the system’s validity at room temperature, the team tested the imaging of different objects at 450 and 890 GHz. The system was affected by humidity, thickness, and material properties. In addition, imaging resolution was discovered to be better as incident frequency increased. The translation step also impacted imaging, showing that the appropriate frequency and translation step must be chosen to meet practical imaging requirements. See “Terahertz-Wave Imaging System Based On Backward Wave Oscillator,” IEEE Transactions On Terahertz Science And Technology, Sept. 2012, p. 504.