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78 results on '"Zhang, Weili"'

15. On/Off Switching of Valley Topological Edge States in the Terahertz Region.

Author

Li, Hongyi, Ouyang, Chunmei, Ma, Jiajun, Liu, Shilei, Liu, Yi, Xu, Quan, Li, Yanfeng, Tian, Zhen, Gu, Jianqiang, Han, Jiaguang, and Zhang, Weili

Abstract

Topological photonic devices provide a powerful platform to control the flow of light because their topologically protected edge states can be immune to backscattering and be robust to impurities, disorders, and defects. As one of the topological photonic systems, valley photonic crystals have attracted great attention because they can achieve a large bandgap and be easily combined with modern micro-nano fabrication technology. Terahertz photonic devices are of enormous interest in next-generation communications. Here, we design a valley photonic crystal consisting of a triangular lattice with three metal rod scatterers. By rotating the three metal rods in opposite directions to break the inversion symmetry, we achieve a bandgap width of up to 70% and observe the transport of the edge states in the terahertz region. By replacing part of the structure with phase change material VO2, on/off switching of the terahertz photonic topological edge states is realized, and the attenuation can be also modeled by adjusting the size of the VO2 region. The proposed regime has potential applications in sensing and 6G communications. [ABSTRACT FROM AUTHOR]

Published
2022
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22. Active Dielectric Metasurfaces for Switchable Terahertz Beam Steering and Focusing.

Author

Chen, Kaiji, Zhang, Xueqian, Chen, Xieyu, Wu, Tong, Wang, Qingwei, Zhang, Ziying, Xu, Quan, Han, Jiaguang, and Zhang, Weili

Abstract

Conventional metasurfaces often manipulate light propagation in a passive way, which cannot satisfy the dynamic operation requirements of many practical applications. Integrating functional materials or components into the structure design is one effective method, which, however, often introduces additional loss to the resonances, thus greatly affecting the efficiency of modulation. Here, we numerically propose a reflection-type dielectric metasurface design that could allow switchable and efficient wavefront control in the terahertz regime. The metasurfaces are composed of dielectric structures suspended on a ground metallic film, which can exhibit different phase responses at different gap distances between them owing to the variation of the Fabre-Pérot (FP) resonance. Two metasurfaces are designed and numerically demonstrated, which can achieve mechanically switchable beam steering and wave focusing responses, respectively, by only changing the gap distance by a small range of 1/3 working wavelength. The maximum efficiency can reach around 89%. The proposed method provides a new avenue towards efficient and active terahertz wavefront control. [ABSTRACT FROM AUTHOR]

Published
2021
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23. All-Dielectric Metasurface-Based Quad-Beam Splitter in the Terahertz Regime.

Author

Lv, Boyang, Ouyang, Chunmei, Zhang, Huifang, Xu, Quan, Li, Yanfeng, Zhang, Xueqian, Tian, Zhen, Gu, Jianqiang, Liu, Liyuan, Han, Jiaguang, and Zhang, Weili

Abstract

Seeking the unprecedented ability of metasurfaces to manipulate terahertz waves in a desired manner has attracted increasing interest. We design and investigate a kind of multi-channel, polarization-dependent transmission-type dielectric metasurface-based terahertz beam splitter. It is numerically demonstrated that such metasurfaces can manipulate terahertz beam, and split it into four channels with alterable angles and orthogonal polarizations, under the linearly polarized incidence with both the x- and y–polarization components. The suggested regime may alleviate the shortage of advanced multifunctional devices and provide extra freedom for terahertz functional device design. [ABSTRACT FROM AUTHOR]

Published
2020
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24. Terahertz Meta-Holograms Reconstruction Based on Compressed Sensing.

Author

Hu, Mengyuan, Tian, Zhen, Chen, Xieyu, Yang, Xingye, Yi, Zhihao, Wang, Qiu, Ouyang, Chunmei, Gu, Jianqiang, Han, Jiaguang, and Zhang, Weili

Abstract

The introduction of single-pixel imaging and compressed sensing (CS) techniques into terahertz (THz) imaging has sped up image acquisition and avoided raster scanning. At present, most single-pixel terahertz imaging developments are based on simple metal samples, researchers rarely study the reconstruction of complex structural samples with large attenuation in the terahertz domain, such as metasurface holographic images. Here, we present an implementation of the single-pixel compressed sensing approach into THz metasurface holography reconstruction. By laser projecting a set of binary patterns on a 500-μm thick silicon wafer using a digital micromirror device (DMD), THz wavefront of the holographic metasurface is spatially encoded. Single-element detector is used to measure electric field amplitude of the transmitted THz radiation for each pattern, and then the hologram is reconstructed by Total variation Augmented Lagrangian and Alternating Direction Algorithm (TVAL3). Besides, the reconstruction effects are also analyzed by reducing measurement number, it can maintain more than 95% of the image information under 20% compression. The demonstrated combination of terahertz holography and single-pixel compressed sensing imaging provides new possibilities for metasurface imaging, verifies the stability of terahertz single-pixel imaging, and the scheme may lead to advances in fast terahertz imaging. [ABSTRACT FROM AUTHOR]

Published
2020
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25. From Terahertz Surface Waves to Spoof Surface Plasmon Polaritons

Author

Xu, Yuehong, primary, Zhang, Ying, additional, Xu, Quan, additional, Zhang, Xueqian, additional, Li, Yanfeng, additional, Gu, Jianqiang, additional, Tian, Zhen, additional, Ouyang, Chunmei, additional, Zhang, Xixiang, additional, Zhang, Weili, additional, and Han, Jiaguang, additional

Published
2018
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30. Manipulate terahertz surface wave with metasurface

Author

Ren, Guanhua, primary, Zhang, Xueqian, additional, Xu, Quan, additional, Li, Yanfeng, additional, Tian, Zhen, additional, Gu, Jianqiang, additional, Ouyang, Chuenmei, additional, Zhang, Weili, additional, and Han, Jiaguang, additional

Published
2016
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39. The Analysis and Simulation of a Hybrid Video Broadcast Architecture

Author

He Lei, Guo Yunfer, Zhang Weili, Ma Hai-long, and Ma Xiangjie

Subjects
Computer science, business.industry, Distributed computing, ComputerSystemsOrganization_COMPUTER-COMMUNICATIONNETWORKS, Locality, Multitree, Overlay, Scheduling (computing), User experience design, Server, Digital Video Broadcasting, Architecture, business, Computer network
Abstract

Recent research efforts have demonstrated the promising potential of building cost-effective media streaming systems on top of peer-to-peer (P2P) networks. The P2P systems have long setup and source to end delay. We proposes a hybrid architecture MTreeTV which combines the use of P2P networks with dedicated streaming servers, and was proposed to build on the advantages of both P2P and CDN paradigms. We offer a novel locality-aware overlay construction and scheduling algorithm to assure the effectiveness of P2P overlay. We also study the placement of the servers with constraints on the client to server paths and evaluate the effect of the server parameters. Through analysis and simulation, we show that MTreeTV supports fast channel switching (ang4s), it can provide high playback continuity (>98%) with little control overload (

Published
2008

40. MTreeTV: A Hybrid Video Broadcast Architecture

Author

He Lei, Ma Hai-long, Guo Yun-Fei, Zhang Weili, and Ma Xiangjie

Subjects
Atomic broadcast, User experience design, business.industry, Computer science, Server, Bandwidth (signal processing), Digital Video Broadcasting, Architecture, business, Broadcast radiation, Computer network, Communication channel
Abstract

To reduce the delay of video broadcast system, we analyze system-capacity in a discrete-time manner. And we propose a hybrid architecture MTreeTV which combines the use of P2P networks with dedicated streaming servers. We also evaluate the effect of the server and client parameters. Through analysis and simulation, we show that MTreeTV supports fast channel switching (

Published
2008

43. Active graphene-silicon hybrid metamaterial devices

Author

Li, Quan, primary, Tian, Zhen, additional, Zhang, Xueqian, additional, Xu, Ningning, additional, Singh, Ranjan, additional, Gu, Jianqiang, additional, Han, Jiaguang, additional, Zhang, Shuang, additional, and Zhang, Weili, additional

Published
2014
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