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-Sharp Toroidal Resonances in Planar Terahertz Metasurfaces

http://onlinelibrary.wiley.com/doi/10.1002/adma.201601611/abstract

A toroidal dipole in metasurfaces provides an alternate approach for the excitation of high-Qresonances. In contrast to conventional multipoles, toroidal dipole interaction strength depends on the time derivative of the surrounding electric field. A characteristic feature of a toroidal dipole is tightly confined loops of oscillating magnetic field that curl around the fictitious arrow of a toroidal dipole vector.

Abstract-Spoof surface plasmon polaritons in terahertz transmission through subwavelength hole arrays analyzed by coupled oscillator model

• 
  • Shan Yin
  • , Xinchao Lu
  • , Ningning Xu
  • , Shuang Wang
  • , Yiwen E.
  • , Xuecong Pan
  • , Xinlong Xu
  • , Hongyao Liu
  • , Lu Chen
  • , Weili Zhang
  •  & Li Wang

http://www.nature.com/articles/srep16440

• Both the localized resonance and excitation of spoof surface plasmon polaritons are observed in the terahertz transmission spectra of periodic subwavelength hole arrays. Analyzing with the coupled oscillator model, we find that the terahertz transmission is actually facilitated by three successive processes: the incident terahertz field first initiates the localized oscillation around each hole, and then the spoof surface plasmon polaritons are excited by the localized resonance, and finally the two resonances couple and contribute to the transmission. Tailoring the localized resonance by hole size, the coupling strength between spoof surface plasmon polaritons and localized resonances is quantitatively extracted. The hole size dependent transmittance and the coupling mechanism are further confirmed by fitting the measured spectra to a modified multi-order Fano model.