Abstract-Z-Shaped toroidal dipole planar terahertz metasurfaces

Jianyu Zhu, Shuang Wang, Xiaoli Zhao, Song Wang, Quan Li,  Tai Chen

https://link.springer.com/article/10.1007%2Fs00340-020-7395-5

We proposed and fabricated a Z-shaped toroidal dipole terahertz metasurfaces, consisting of two incomplete U-shaped split rings, and the two incomplete U-shapes are rotationally symmetric with respect to the Z-axis. The effects of the structural parameters on the electromagnetic characteristics of toroidal resonances are investigated via simulation and experiment. The mechanism of toroidal dipole resonance is studied deeply by establishing an LC resonance model and calculating the multipoles scattering energy. The capacitance was highly depended on the value of lx, and the inductance was determined by the value of ly. Hence, the red shift was observed as the increasing of ly/lx. The resonant frequency of the toroidal dipole resonance is red shifted, as the ly/lx of the metallic pattern increases. The tunability of toroidal dipole resonant frequencies explores the interaction of toroidal multipoles with terahertz wave that could have extensive applications in the terahertz functional devices.

Abstract-The investigation of the electromagnetic coupling effect in terahertz toroidal metasurfaces and metamaterials

Shuang Wang, Xiaoli Zhao, Song Wang, Quan Li, Jianyu Zhu,  Lei Han



https://www.sciencedirect.com/science/article/pii/S2238785419321970

We proposed and fabricated toroidal dipole (TD) metasurfaces(MSs) with a metamolecule of two coplanar U-shaped split ring resonators(USRRs) fabricated on polyimide substrate, and TD metamaterials (MMs) were the stacks of two TD MSs layers, whose frequencies, electromagnetic (EM) distributions and Q factor can be efficiently affected by the EM coupling effect in TD MSs/MMs. It was found that the resonances frequencies of TD MMs were shifted to lower frequencies due to the increase of inductance by the stacks of metallic layer. Meanwhile, the high-frequency TD resonance in TD MMs would be tailored by the periodicity. Considering the relation between TD resonances and the scattering power of TD (Ty), the Q factor depended highly on the value of Ty in the same metamolecule structure. The optimization in excitation of TD provide opportunity to further increase the Q-factor of metamaterial and pave a way for potential applications in terahertz sensor and other functional devices.

Abstract-C-shaped split ring resonator terahertz toroidal dipole metasurfaces

Shuang Wang, Xiaoli Zhao, Song Wang, Jianyu Zhu, Quan Li, and Yaxin Wang

Fig. 2. (a) Experimental, (b)Simulated amplitude transmission spectra for samples, surface current, and (c) Magnetic field distribution (on the XZ plane at Y = 0) at ω2resonances of the design with different values of θ, (d) and (e) Schematics of the formation of head-to-tail arrangement correlating at ω1 and ω2, respectively.

https://www.osapublishing.org/ome/abstract.cfm?uri=ome-9-9-3657

We designed and fabricated terahertz toroidal dipole metasurfaces based on a C-shaped split ring resonator metallic pattern fabricated on a flexible dielectric material (mylar). The toroidal dipole moment (Ty) was demonstrated as the dominant contribution to two different resonances at low frequency (ω1) and at high frequency (ω2). Simulation and LC circuit model analysis offered a quantitative explanation to the blue shift of the resonant frequencies at ω1and ω2 as the increase of the opening angle(θ). The resonant frequencies showed a red shift at ω1 and ω2 as the increase of the outer ring radius (QR). Furthermore, the enhancement of the Q factor was attributed to the increase of Ty and the decrease of radiative loss. It was further proven that the model provided a new scheme for designing the toroidal dipole metasurfaces under a terahertz band, which was expected to be used as terahertz functional devices.

© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Tailoring Terahertz Propagation by Phase and Amplitude Control in Metasurfaces

Jingjing Zheng, Xueqian Zhang, Lixiang Liu, Quan Li, Leena Singh, Jiaguang Han, Fengping Yan, Weili Zhang

https://link.springer.com/article/10.1007/s10762-017-0379-9

Metasurfaces have been very successful at demonstrating the ability to control the wave propagation over the broad electromagnetic spectrum in recent years. The output wavefronts can be controlled at will, by encoding specially designed abrupt changes of electromagnetic parameters into the metasurfaces, such as phase and amplitude. Constituted by a single- or few-layer of planar structures, metasurfaces are straightforward in design and fabrication, thus promising many credible applications. Moreover, such control concept can be further extended to the surface wave regime. In this review, we present our recent progress on metasurfaces capable of tailoring the propagation of both free-space and surface terahertz waves. Following an introduction of the basic concept and theory, a number of unique terahertz metasurfaces are presented, showing the ability to device ultra-thin and compact functional terahertz components.

Abstract-Active graphene–silicon hybrid diode for terahertz waves

• 
  

• Quan Li,
• Zhen Tian,
• Xueqian Zhang,
• Ranjan Singh,
• Liangliang Du,
• Jianqiang Gu,
• Jiaguang Han
• & Weili Zhang

http://www.nature.com/ncomms/2015/150511/ncomms8082/full/ncomms8082.html

Controlling the propagation properties of the terahertz waves in graphene holds great promise in enabling novel technologies for the convergence of electronics and photonics. A diode is a fundamental electronic device that allows the passage of current in just one direction based on the polarity of the applied voltage. With simultaneous optical and electrical excitations, we experimentally demonstrate an active diode for the terahertz waves consisting of a graphene–silicon hybrid film. The diode transmits terahertz waves when biased with a positive voltage while attenuates the wave under a low negative voltage, which can be seen as an analogue of an electronic semiconductor diode. Here, we obtain a large transmission modulation of 83% in the graphene–silicon hybrid film, which exhibits tremendous potential for applications in designing broadband terahertz modulators and switchable terahertz plasmonic and metamaterial devices.