International Journal of Terahertz Science and Technology
Vol.14, No.4, December 2021. PP.71-90(2)
date2021-12-31 09:25:13 Click No.237

TST, Vol. 14, No. 4, PP. 71-82

(Invited paper) Three-dimensional helix terahertz metamaterials with mechanical tunability

Yonggang Piao 1†, Helin Li 1, 3†, Zhongyang Bai 4, Haowei Sun 3, 4, Xinyu Wu 5, Tong Sun 1, 3, Yousheng Zhou 1, Qinghe Ye 1, Michael Kraft 5, Xiaojun Wu 4, Tianxiao Nie 1, 2, 3, Weisheng Zhao 1, 3 and Lianggong Wen 1*, 2, 3
1 School of Integrated Circuit Science and Engineering, Beihang University, Beijing, 100191, China.
2 Beihang Hangzhou Innovation Institute Yuhang, Beihang University, Xixi Octagon City, Yuhang District, Hangzhou, 310023, China.
3 Beihang-Goertek Joint Microelectronics Institute, Qingdao Research Institute of Beihang University, Qingdao, 266000, China.
4 School of Electronics and Information Engineering, Beihang University, Beijing 100191, China.
5 MNS-MICAS, KU Leuven, Leuven-3001, Belgium.
These authors contributed equally to this paper.
*1 Email:
wenlg@buaa.edu.cn

(Received November 18, 2021)

Abstract: Terahertz polarization modulation plays a key role in a variety of applications, and terahertz metamaterials composed of artificially designed structures can modulate terahertz waves efficiently. These structures determine the electromagnetic properties of the metamaterial, resulting in effective control of the electromagnetic (EM) effects. Currently, most of the active metamaterial is based on planar unit structures, which can be modulated by using electrical, optical, thermal and magnetic methods. In this paper, a 3D helix metamaterial is proposed, which is fabricated by projection micro stereolithography and atomic layer deposition (ALD). The operation condition modelling proved that the helix metamaterials can transform a THz linear polarization wave to a right-handed circular polarization wave. The experimental result also shows that the polarization rotation angle increases from 14.1< to 26.0< and the ellipticity angle decreases from 23.5< to 9.2< with the pitch of the helical structure varying from 157 μm to 250 μm at 0.27 THz. Furthermore, the maximum range of terahertz circular dichroism varies from -6.0< to 30.0< in the same conditions. By changing the structural parameters mechanically or combining with other adjustable mechanical devices, the metamaterials are expected to enable more extensive applications with EM interference resistance, using merely mechanical control methods.

Keywords: Terahertz, 3D helix metamaterial, Projection micro-stereo-lithography, Polarize modulation, Mechanical control

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TST, Vol. 14, No. 4, PP. 83-90

(Invited paper) Terahertz holographic imaging using 3D-printed metasurfaces

Jierong Cheng, Yiwu Yuan, Xipu Dong, Shengjiang Chang *
Nankai University, Institute of Modern Optics,
Tianjin Key Laboratory of Micro-Scale Optical Information Science and Technology,
38 Tongyan Rd, P. O. Box 300350, Tianjin, China
* Email:
sjchang@nankai.edu.cn

(Received December 20, 2021)

Abstract: Metasurfaces significantly promote the development of holography by encoding the desired amplitude and phase modulation profile through subwavelength artificially designed resonators. Most of the dielectric metasurface holograms use high-index dielectric to avoid near field coupling. Here taking advantages of the diverse THz-transparent low-index polymers and the advanced 3D printing technique, we study the holographic imaging based on 3D-printed low-index metasurfaces. The phase hologram is calculated based on the Rayleigh-Sommerfeld diffraction theory and the Gerchberg-Saxton algorithm, which is implemented by polymer rods with varied dimensions and refractive index of 1.57. The simulation and consistent experimental results show that 3D-printed low-index dielectric metasurfaces offer a low-cost and time-saving scheme for wavefront transformation at terahertz frequencies.

Keywords: Terahertz, Hologram, Metasurface, 3D Printing, Refractive index

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