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Free control of far-field scattering angle of transmission terahertz wave using multilayer split-ring resonators'metasurfaces

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Frontiers of physics 2020年第6期15卷 125-132页

作者： Ying Tian Xufeng Jing Haiyong Gan chenxia li Zhi Hong Institute of Optoelectronic Technology China Jiliang UniversityHangzhou 310018China National Institute of Metrology Beijing 102200China

To enhance transmission eficiency of Pancharatnam Berry(PB)phase metasurfaces,multilayer split-ring resonators were proposed to develop encoding *** per the generalized Snell's law,the deflection angle of the PB phase encoding metasurfaces depends on the metasurface period's ***,it is impossible to design an infinitesimal metasurface unit;consequently,the continuous transmission scattering angle cannot be *** digital signal processing,this study introduces the Fourier convolution principle on encoding metasurface sequences to freely control the trausmitted scattering *** addition and subtraction operations between two diferent encoding sequences were then performed to achieve the continuous variation of the scattering ***,we established that the Fourier convolution principle can be applied to the checkerboard coded metasur-faces.

关键词： metamaterial metasurface scattering Fourier convolution

Broadband cross-circular polarization carpet cloaking based on a phase change material metasurface in the mid-infrared region

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Frontiers of physics 2022年第5期17卷 83-91页

作者： Bo Fang Dantian Feng Peng Chen lijiang Shi Jinhui Cai Jianmin li chenxia li Zhi Hong Xufeng Jing College of Metrology&Measurement Engineering China Jiliang UniversityHangzhou 310018China Institute of Optoelectronic Technology China Jiliang UniversityHangzhou 310018China Centre for THz Research China Jiliang UniversityHangzhou 310018China Hangzhou Hangxin Qihui Technology Co. LtdHangzhou 310026China University of Shanghai for Science and Technology No.516 Jung Gong RoadShanghai 200093China

In view of the fact that most invisibility devices focus on linear polarization cloaking and that the characteristics of mid-infrared cloaking are rarely studied,we propose a cross-circularly polarized invisibility carpet cloaking device in the mid-infrared *** on the Pancharatnam–Berry phase principle,the unit cells with the cross-circular polarization gradient phase were carefully designed and constructed into a *** order to achieve tunable cross-circular polarization carpet cloaks,a phase change material is introduced into the design of the unit *** the phase change material is in amorphous and crystalline states,the proposed metasurface unit cells can achieve highefficiency cross-polarization conversion,and reflection intensity can be *** to the phase compensation principle of carpet cloaking,we construct a metasurface cloaking device with a phase gradient using the designed unit *** the near-and far-field distributions,the cross-circular polarization cloaking property is confirmed in the broadband wavelength range of 9.3–11.4μ*** proposed cloaking device can effectively resist detection of cross-circular polarization.

关键词： metamaterial metasurface cloaking

Rupture segmentation and slip partitioning of the mid-eastern part of the Kunlun Fault,north Tibetan Plateau

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Science China Earth Sciences 2011年第11期54卷 1730-1745页

作者： li chenxia XU XiWei WEN XueZe ZHENG RongZhang CHEN GuiHua YANG Hu AN YanFen GAO Xiang Institute of Geology China Earthquake Administration National Center of Active Fault Studies Beijing 100029 China Lanzhou Seismological Institute of China Earthquake Administration Lanzhou 730000 China Earthquake Administration of Sichuan Province Chengdu 610041 China

The Kunlun Fault, an active fault on the border between the Bayan Har and Kunlun-Qaidam blocks, is one of the major left lateral strike-slip faults in the Tibetan Plateau. Previous research has not reached a consensus on agreeable slip rates along much of its length and the slip rate gradient along the eastern part, both of which play critical roles in a range of models for the eastward extrusion and thickened crust of the Tibetan Plateau. New slip rates have been determined at sites along the eastern part of the Kunlun Fault by dating deposits and measuring atop displaced fluvial terrace risers. Field investigations and interpretation of satellite images reveal geometrical features of the fault and the late Quaternary offset, new earthquake ruptures and surface-rupturing segmentation, from which long-term slip rates and earthquake recurrence intervals on the fault are estimated. The tectonic geomorphology method has determined that the long-term horizontal slip rates on the Tuosuohu, Maqin and Ma- qu segments from west to east are 11.2±1, 9.3±2, and 4.9±1.3 mm/a while their vertical slip rates are 1.2±0.2, 0.7±0.1, and 0.3 mm/a in the late Quaternary. Results indicate that the slip rates regularly decrease along the eastern -300 km of the fault from 〉10 to 〈5 mm/a. This is consistent with the decrease in the gradient such that at the slip rate break point is at the triple point intersection with the transverse fault, which in turn is transformed to the Awancang Fault. The vector decomposition for this tectonic transformation shows that the western and eastern branches of the Awancang Fault fit the slip-partitioning mode. The slip rate of the southwestern wall is 4.6 mm/a relative to the northeastern wall and the slip direction is 112.1°. The mid-eastern part of the Kunlun Fault can be divided into three independent segments by the A＇nyemaqen double restraining bend and the Xigongzhou intersection zone, which compose the surface rupture segmentation indicators for t

关键词： mid-eastern Kunlun Fault slip rate surface rupture segmentation slip partition paleoearthquake Tibetan Plateau

Improvement of terahertz beam modulation efficiency for baseless all-dielectric coded gratings

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Photonics Research 2023年第10期11卷 1738-1750页

作者： JIE JIANG BO FANG chenxia li ZHI HONG XUFENG JING Institute of Optoelectronic Technology China Jiliang UniversityHangzhou 310018China Centre for THz Research China Jiliang UniversityHangzhou 310018China College of Metrology&Measurement Engineering China Jiliang UniversityHangzhou 310018China

Optical metasurfaces are two-dimensional ultrathin devices based on single-layer or multilayer arrays of subwave-length nanostructures. They can achieve precise control of phase, amplitude, and polarization on the subwave-length scale. In this paper, a substrate-free all-silicon coded grating is designed, which can realize the phase control of the outgoing beam after the y-polarized plane wave is vertically incident on the metasurface at 0.1 *** a single-layer silicon nanoarray structure, a low-reflection anomalous transmission metasurface is realized, and a variety of different beam deflectors are designed based on these encoded gratings. We propose a coded grating addition principle, which adds and subtracts two traditional coded grating sequences to obtain a new coded grating sequence. The encoded supergrating can flexibly control the scattering angle, and the designed substrate-free all-silicon encoded grating can achieve a deflection angle of 48.59°. In order to verify the principle of coded grating addition, we experimented with cascade operation of two coded sequence gratings to obtain the flexible control of the terahertz beam of the composite supergrating. The principle of grating addition provides a new degree of freedom for the flexible regulation of the terahertz wavefront. At the same time, this method can be extended to the optical band or microwave band, opening up new ways for electromagnetic wave manipulation and beam scanning.

关键词： polarization beam dielectric

Flexible tuning of multifocal holographic imaging based on electronically controlled metasurfaces

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Photonics Research 2024年第1期12卷 61-69页

作者： OWEN ZENG chenxia li BO FANG ZHI HONG XUFENG JING Institute of Optoelectronic Technology China Jiliang UniversityHangzhou 310018China Centre for THz Research China Jiliang UniversityHangzhou 310018China College of Metrology&Measurement Engineering China Jiliang UniversityHangzhou 310018China

Programmable hyper-coded holography has the advantage of being programmable as well as being flexibly *** coded metamaterials with excellent electromagnetic modulation capability and the ability to control the phase to modulate the spatial radiation field through external excitation in the form of switching can be used to realize low-cost digital *** design a 1-bit encoded programmable metasurface,which is electrically connected to control the PIN diode in the switching state and to switch the condition of each metasurface cell between“0”and“1.”Using the designed programmable metasurface,we can randomly encode the cell structure to realize single-focus focusing,multi-focusing,and simple holographic letter *** on the nonlinear holographic model,we employ the Gerchberg-Saxton improvement algorithm to modulate the energy distribution at the focus by adjusting the phase ***,we introduce the Fourier convolution principle to regulate the holographic imaging focus flexibly.

关键词： holographic letter excitation

Parameters of Coseismic Reverse- and Oblique-Slip Surface Ruptures of the 2008 Wenchuan Earthquake,Eastern Tibetan Plateau

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Acta Geologica Sinica(English Edition) 2009年第4期83卷 673-684页

作者： XU Xiwei YU Guihua CHEN Guihua RAN Yongkang li chenxia CHEN Yuegau CHANG Chungpai Institute of Geology China Eathquake Administrative Beijing 100029 Department of Geosciences National Taiwan University Taipei Center for Space and Remote Sensing Research National Central University Jhongli Taipei

On May 12th, 2008, the Mw7.9 Wenchuan earthquake ruptured the Beichuan, Pengguan and Xiaoyudong faults simultaneously along the middle segment of the Longmenshan thrust belt at the eastern margin of the Tibetan plateau. Field investigations constrain the surface rupture pattern, length and offsets related to the Wenchuan earthquake. The Beichuan fault has a NE-trending rightlateral reverse rupture with a total length of 240 km. Reassessment yields a maximum vertical offset of 6.5±0.5 m and a maximum right-lateral offset of 4.9±0.5 m for its northern segment, which are the largest offsets found; the maximum vertical offset is 6.2±0.5 m for its southern segment. The Pengguan fault has a NE-trending pure reverse rupture about 72 km long with a maximum vertical offset of about 3.5 m. The Xiaoyudong fault has a NW-striking left-lateral reverse rupture about 7 km long between the Beichuan and Pengguan faults, with a maximum vertical offset of 3.4 m and left-lateral offset of 3.5 m. This pattern of multiple co-seismic surface ruptures is among the most complicated of recent great earthquakes and presents a much larger danger than if they ruptured individually. The rupture length is the longest for reverse faulting events ever reported.

关键词： surface rupture zone coseismic offset Wenchuan earthquake Longmenshan

All-dielectric double-layer honeycomb tunable metamaterial absorber with integrated gold nanoparticles

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Photonics Research 2024年第10期12卷 2344-2353页

作者： YIXIN liU YING TIAN chenxia li BO FANG JIANJUN liU ZHI HONG XUFENG JING Institute of Optoelectronic Technology China Jiliang UniversityHangzhou 310018China Centre for THz Research China Jiliang UniversityHangzhou 310018China College of Metrology&Measurement Engineering China Jiliang UniversityHangzhou 310018China College of Information Engineering China Jiliang UniversityHangzhou 310018China

The optical regulation strategy of gold nanoparticles can significantly improve the performance of terahertz *** designed an all-dielectric double-layer honeycomb metamaterial absorber(MA)to demonstrate the broadband terahertz absorption characteristics in the presence or absence of gold *** it does not contain gold nanoparticles,MA exhibits a peak absorption efficiency of over 99%within the bandwidth range of∼486 *** particular,gold nanospheres(AuNPs),gold nanobipyramids(AuNBPs),and gold nanorods(AuNRs)are used to modulate the optical coupling effect of metamaterial absorbers,which improves their modulation *** the simulation,the effective medium theory(EMT)was applied to quantitatively calculate the optical response of a metamaterial absorber with an integrated gold nanoparticle equivalent gold *** integrated gold nanoparticle equivalent gold layer can achieve modulation enhancement of one order of *** the experiment,our process is compatible with CMOS technology,which may contribute to the development of terahertz *** addition,the tunability and modulation enhancement characteristics demonstrated are beneficial for creating dynamic functional terahertz devices,such as THz modulators and switches.

关键词： nanoparticles absorber dielectric

A Discussion of Some Problems Concerning the Tosonhu Lake M_S7.5 Earthquake in 1937

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Earthquake Research in China 2007年第1期21卷 94-103页

作者： li chenxia Dai Huaguang Chen Yongming Xu Xiwei Dai Wei Institute of Geology China Earthquake Administration Beijing 100029 China Lanzhou Base of Institute of Earthquake Science CEA Lanzhou 730000 China

The East Kuulun active fault zone, which lies in the valley of the Kuulun Mountains above an elevation of 4,000 meters, is an important active fault zone in the Northeast Qinghai-Xizang （Tibet） Plateau. The 1937, the Tosonhu lake Ms7. 5 earthquake occurred in the eastern segment of the East Kuulun active fault zone. Four field investigations were launched on this seism in 1963, 1971, 1980, and between 1986 and 1990. However, due to different extents of the investigations, four different conclusions have been gained. Concerning the length aspect of the surface rupture zone of this earthquake, the unanimous consensus is that its eastern end lies in the west side of the main Ridge of the A ＇nyemaqen Mountains, but opinions about the western end and the location of the macro-epicenter are different. Based on investigation and comprehensive study, a series of scientific problems like geometric and kinetic characteristics, the length of the rupture zone, the maximum sinistral horizontal displacement and the macroepicenter were re-evaluated. We believe that the total length of this earthquake＇s surface deformation zone is at least 240km; the western end of the zone is at the west of Wnsuwuwoguole; the maximum sinistral horizontal displacement is 8m to the west of Baerhalasha gully on the east side of Sanchakou; the maximum vertical displacement is 3.5m in the south of Sanchakou and the macro-epicenter is in Sanchakou.

关键词： The East Kuulun active fault zone The 1937 Tosonhu lake Ms7.5 earthquake Earthquake surface rupture zone Macro-epicenter

Er^(3+)/Tm^(3+)/Yb^(3+)tridoped oxyfluoride glass ceramics with efficient upconversion white-light emission

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Chinese Optics Letters 2010年第1期8卷 66-69页

作者：李晨霞徐时清叶仁广赵士龙邓德刚庄松林 School of Optical-Electrical and Computer Engineering University of Shanghai for Science and Technology College of Optical and Electronic Technology China Jiliang University

A novel Tm^3＋/Yb^3＋ triply-doped glass ceramics containing BaF2 nano-crystals are successfully prepared. Fluoride nanocrystals BaF2 are successfully precipitated in glass matrix, which is affirmed by the X-ray diffraction results. The intense blue （476 nm）, green （543 nm）, and red （656 nm） emissions of the glass ceramics are simultaneously observed at room temperature under 980-am excitation, and the emission luminescence intensity increases significantly compared with the precursor glass, which is attributed to the low phonon energy of fluoride nanocrystals when rare-earth ions are incorporated into the precipitated BaF2 nanocrystals. Under 980-nm excitation at 400 mW, the international commission on illumination （CIE） chromaticity coordinate （X = 0.278, Y = 0.358） of the tridoped oxyfluoride glass ceramics＇ upconversion emissions is close to the standard white-light illumination （X = 0.333, Y= 0.333）. The results indicate that Tm^3＋/Yb^3＋ triply doped glass ceramics can act as suitable materials for potential three-dimensional displays applications.

关键词： Barium compounds Erbium light Luminescence Nanocrystals X ray diffraction Ytterbium