Abstract-High-efficiency Huygens’ metasurface for terahertz wave manipulation

Ruiqiang Zhao, Zheng Zhu, Guohua Dong, Tingting Lv, Yuxiang Li, Chunying Guan, Jinhui Shi, and Han Zhang

https://www.osapublishing.org/ol/abstract.cfm?uri=ol-44-14-3482

A fair amount of theoretical work has shown that Huygens’ metasurfaces well modulate electromagnetic waves by properly designing electrical impedance 𝑍𝑒𝑠$Z_{es}$ and magnetic admittance 𝑌𝑚𝑠$Y_{ms}$; however, the transmissive Huygens’ metasurface is still challenging in the terahertz band. In this work, a transmission-type Huygens’ metasurface with bilayer metallic patches has been proposed and theoretically demonstrated to show a reflectionless phase modulation for a linearly polarized terahertz wave. The simulation results show that the metasurface can achieve 2𝜋$2\pi$ phase coverage, and importantly the phase change can be simply achieved by changing a single geometric parameter of the metamolecule, along with a similar transmission effect. We design a high-efficiency beam deflector to realize an anomalous refraction with an angle of 19.8°. The proposed metasurface will provide a simple and direct way to realize efficient terahertz devices for wavefront manipulation.

© 2019 Optical Society of America

Abstract-Tailoring polarization and magnetization of absorbing terahertz metamaterials using a cut-wire sandwich structure

Hadi Teguh Yudistira, Shuo Liu,  Tie Jun Cui,  Han Zhang

a) Illustration of cut-wire sandwich structure. W, L, g, Zd and Zg are width of cut wire (20 µm), length of cut wire (100 µm), the gap size of cut wire with its neighbor (5 µm), polyimide substrate thickness (5 µm), and tge cut-wire structure thickness (100 nm), respectively. D is the lattice constant (D = L + g). b) Sample 1: cut-wire sandwich structure, c) Sample 2: cross-shaped sandwich structure, d) Sample 3: star-shaped sandwich structure.

https://www.beilstein-journals.org/bjnano/articles/9/136

The permittivity and permeability of a cut-wire sandwich structure can be controlled by laterally shifting the upper and lower layers. The use of this process for designing specific application-oriented devices may lack clear-cut guidelines because the lateral misalignment will significantly change the permittivity and permeability simultaneously. Therefore, in this work, we designed, fabricated and characterized a cut-wire sandwich device capable of tailoring the polarization and magnetization separately, thereby providing a promising recipe for achieving specific application objectives, such as a high-performance absorber. Accumulated charges effectively provided the polarization at the edge of cut-wires, and the surface current density on the cut-wires at top and bottom layers effectively generated the magnetization. By controlling and optimizing the geometrical configurations of the entire sandwich device (without lateral misalignment), the impedance could be matched to that of free space while generating a large imaginary part in the refractive index. This work characterizes the absorption performance of such sandwich structures in the terahertz regime. This mechanism could be further extended to other metamaterial devices in the terahertz and other frequency ranges because polarization and magnetization can now be selectively controlled in a straightforward manner.

Abstract-THz Photonics in Two Dimensional Materials and Metamaterials: Properties, Devices and Prospects

Jinhui Shi,  Zhongjun Li,  David K. Sang,  Yuanjiang Xiang,  Jianqing Li,  Shuang Zhang,  Han Zhang

http://pubs.rsc.org/en/content/articlelanding/2018/tc/c7tc05460b#!divAbstract

Terahertz radiation refers to a broad electromagnetic spectrum range between microwave and infrared waves, which is also known as terahertz gap due to inadequate materials and technologies for its generation and manipulation. Atomically thin two dimensional (2D) materials such as graphene, black phosphorus (BP) and transition metal dichalcogenides (TMDs) provide a powerful platform for manipulating the propagation and detection of terahertz waves. Furthermore, hybrid meta-materials that feature the combination of artificially engineered meta-materials and 2D materials greatly facilitate dynamic modulation or manipulation of THz radiation towards novel terahertz applications. Herein, we review recent progress on 2D materials in the terahertz domain and hybrid metamaterials with engineered functionalities through the incorporation of graphene, TMDs and BPs. The emerging THz devices based on the modulation, nonlinearity, filtering, and Plasmonics of 2D Materials and Metamaterials will be highlighted, and a brief discussion with perspectives and the remaining challenges will be concluded.

Abstract-Characterization of cocrystals formed by grinding amino acids through terahertz time-domain spectroscopy

• Xiaoyan Zhao, 
• Haixia Su, 
• Zhaohui Zhang, 
• Zhi Li, 
• Han Zhang, 
• Tianyao Zhang

http://link.springer.com/article/10.1007%2Fs11434-014-0432-1

In this paper, we used terahertz time-domain spectroscopy (THz-TDS) over a range of 0.3–2.5 THz to investigate the formation of solid-state cocrystals of amino acids, formed by grinding mixtures of two different kinds of amino acids. For comparison, we prepared dual-layer samples, combined by pressing two single-component pellets together without grinding. In the ground-mixture samples, some extra absorption peaks appeared, different from the characteristic peaks of the pure components, but these peaks did not appear in the dual-layer samples. Thus, these extra absorption peaks in the THz range are unique features of cocrystals. From our results, we believe that THz-TDS is a promising technique to characterize cocrystals.