Abstract-The Influence on the Q Value of the THz Meta-surface From the Tip Charge Accumulation Coupling

Han Sun,  Lan Wang, Yaxin Zhang, Feng Lan, Shixiong Liang, Kang Xue, Ziqiang Yang,

https://ieeexplore.ieee.org/document/8691625

With the adventure of metamaterials, there has been a tremendous advancement in the manipulation of the terahertz (THz) wave. However, the excitation of high-Q-factor resonance has been a great challenge in traditional metamaterials due to the ohmic and radiation losses. In this paper, the influence of the tip charge accumulation effect on the high-Q value meta-surface has been studied within the triangular array meta-surface. It is found that when the tip charges accumulation resonance from each pair of triangular units can couple with each other to construct a significant resonant mode which could trap more energy to achieve higher Q value. Moreover, the stacking of the induced charges distributed at the surface of the meta-unit making the coupling strength is further increased so that the strong tip charge accumulation effect could also affect the Q-value. The experiment verified this phenomenon, which shows the stronger coupling resonance and tip charges accumulation could result in the enhancement of the Q-value. This research has potential applications in high-Q THz devices.

Abstract-Linear polarization conversion of transmitted terahertz wave with double-layer meta-grating surfaces

Han Sun, Yaxin Zhang, Kailong Wang, Yuncheng Zhao, Wei Kou, Shixiong Liang, Jiaguang Han, and Ziqiang Yang

https://www.osapublishing.org/col/abstract.cfm?uri=col-16-8-081601

In this Letter, we demonstrate a linear polarization conversion of transmitted terahertz wave with double-layer meta-grating surfaces, which integrated the frequency selectivity of a split ring resonator metasurface and the polarization selectivity of a metallic grating surface. Since the double-layer can reduce the loss, and the Fabry–Perot like resonant effect between the two layers can improve the conversion efficiency, this converter can rotate the incident y-polarized terahertz wave into an x-polarized transmitted wave with relatively low loss and high efficiency. Experimental results show that an average conversion efficiency exceeding 75% from 0.25 to 0.65 THz with the highest efficiency of 90% at 0.43 THz with only −2  dB loss has been achieved.

© 2018 Chinese Laser Press

Abstract-Mode coupling in terahertz metamaterials using sub-radiative and super-radiative resonators

Shen Qiao¹, Yaxin Zhang^1,a), Yuncheng Zhao¹, Shixiong Liang², Gaiqi Xu¹, Han Sun¹ and Ziqiang Yang¹
http://scitation.aip.org/content/aip/journal/jap/118/19/10.1063/1.4936169?TRACK=RSS
a) Author to whom correspondence should be addressed. Electronic mail:Zhangyaxin@uestc.edu.cn
J. Appl. Phys. 118, 193104 (2015); http://dx.doi.org/10.1063/1.4936169

We theoretically and experimentally explored the electromagnetically induced transparency (EIT) mode-coupling in terahertz (THz) metamaterialresonators, in which a dipole resonatorwith a super-radiative mode is coupled to an inductance-capacitance resonator with a sub-radiative mode. The interference between these two resonators depends on the relative spacing between them, resulting in a tunable transparency window in the absorptionspectrum.Mode coupling was experimentally demonstrated for three spacing dependent EITmetamaterials. Transmittance of the transparency windows could be either enhanced or suppressed, producing different spectral linewidths. These spacing dependent mode-couplingmetamaterials provide alternative ways to create THz devices, such as filters, absorbers, modulators, sensors, and slow-light devices.

Abstract-Gbps terahertz external modulator based on a composite metamaterial with a double-channel heterostructure

Yaxin Zhang , Shen Qiao , Shixiong Liang , Zhenhua Wu , Ziqiang Yang , Zhihong Feng , Han Sun , Yucong Zhou , Linlin Sun , Zhi Chen , Xianbing Zou , Bo Zhang , Jianhao Hu , Shaoqian Li ,Qin Chen , Ling Li , Gaiqi Xu , Yuncheng Zhao , and Shenggang Liu

Nano Lett., Just Accepted Manuscript

DOI: 10.1021/acs.nanolett.5b00869

Publication Date (Web): April 28, 2015

Copyright © 2015 American Chemical Society

http://pubs.acs.org/doi/abs/10.1021/acs.nanolett.5b00869

The past few decades have witnessed a substantial increase in terahertz (THz) research. Utilizing THz waves to transmit communication and imaging data has created a high demand for phase and amplitude modulation. However, current active THz devices, including modulators and switches, still cannot meet THz system demands. Double-channel heterostructures, an alternative semiconductor system, can support nano-scale two-dimensional electron gases (2DEGs) with high carrier concentration and mobility and provide a new way to develop active THz devices. In this article, we present a composite metamaterial structure that combines an equivalent collective dipolar array with a double-channel heterostructure to obtain an effective, ultra-fast and all-electronic grid-controlled THz modulator. Electrical control allows for resonant mode conversion between two different dipolar resonances in the active device, which significantly improves the modulation speed and depth. This THz modulator is the first to achieve a 1-GHz modulation speed and 85% modulation depth during real-time dynamic tests. Moreover, a 1.19-rad phase shift was realized. A wireless free-space-modulation THz communication system based on this external THz modulator was tested using 0.2-Gbps eye patterns. Therefore, this active composite metamaterial modulator provides a basis for the development of effective and ultra-fast dynamic devices for THz wireless communication and imaging systems.

Abstract-Controlling the transparency window in terahertz band using mode coupling metamaterials

Shen Qiao¹, Yaxin Zhang^1,a), Gaiqi Xu¹, Linlin Sun¹, Han Sun¹, Ling Li¹,Shixiong Liang², Yuncheng Zhao¹ and Ziqiang Yang¹
http://scitation.aip.org/content/aip/journal/jap/117/6/10.1063/1.4907870
1 Terahertz Science Cooperative Innovation Center, University of Electronic Science and Technology of China, Chengdu 610054, China
2 National Key Laboratory of Application Specific Integrated Circuit, Hebei Semiconductor Research Institute, Shijiazhuang 050051, China
a) Author to whom correspondence should be addressed. Electronic mail: Zhangyaxin@uestc.edu.cn
J. Appl. Phys. 117, 063103 (2015); http://dx.doi.org/10.1063/1.4907870

Mode-coupling metamaterials are typically composite structures with different resonance modes. Controlling couplings among these modes results in a sharp transparency window within the absorption spectrum of the metamaterials. Here, we present a composite structure of ring and split-ring resonators to constitute a new structure with entirely new mode. Experimental results show that the asymmetric combination of these resonators can result in a variation in transparency strength. The dimensions and relative positions of the split-ringresonator are discussed particularly with a series of experimental results. Simulation results show that the coupling intensity is the main reason for this behavior. Exploiting this aspect, a way to control the transparency window between composite structure metamaterials is proposed.