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Terahertz magneto-optical isolator based on graphene-silicon waveguide

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Science China(Information Sciences) 2022年第6期65卷 275-276页

作者： Dan ZHAO Fei FAN Tengfei LI Zhiyu TAN Jierong CHENG shengjiang chang Institute of Modern Optics Nankai University Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology College of Electronic Information and Optical Engineering Nankai University Tianjin Key Laboratory of Optoelectronic Sensor and Sensing Network Technology College of Electronic Information and Optical Engineering Nankai University

Dear editor,Optical isolators and circulators are non-reciprocal one-way transmission devices, which only allow light to transmit in one direction and prevent light from transmitting in the opposite direction. Thus, they can protect the light source and detector in the integrated microwave or optical system, and also significantly reduce the additional noises. However, due to the limitation of material and device mechanism,

关键词： graphene magneto-optical device isolator Waveguide Terahertz

Control of angular dispersion in dielectric gratings for multifunctional wavefront shaping and dynamic polarization conversion

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Photonics Research 2021年第11期9卷 2190-2195页

作者： YIWU YUAN JIERONG CHENG FEI FAN XIANGHUI WANG shengjiang chang Institute of Modern Optics Nankai UniversityTianjin 300350China Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology Tianjin 300350China Tianjin Key Laboratory of Optoelectronic Sensor and Sensing Network Technology Tianjin 300350China

Compared with traditional optical elements,metasurfaces have shown unique advantages in multifunctionality encoded in different frequencies,polarization states,and orbital angular ***,the study of metasurfaces with well-controlled functions under different incident angles is still in its *** we propose a general method to tailor the angular dispersion over the simplest binary dielectric grating in the transmission *** demonstrate that the angular response is strongly related to the number of waveguide modes inside the grating,so one can intentionally reduce or enhance the angular dispersion by controlling the number of waveguide *** phase manipulation over incident angles is experimentally demonstrated by a metalens with angle-dependent *** angular dispersion in orthogonal polarization states is further utilized to demonstrate angle-insensitive and angle-multiplexed wave *** devices with simple configuration and clear physics offer a general platform to expand the scope of beam manipulation over metasurfaces.

关键词： polarization waveguide dispersion

Arbitrary large-gradient wavefront shaping: from local phase modulation to nonlocaldiffraction engineering

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Photonics Research 2022年第4期10卷 896-904页

作者： Xipu Dong Jierong Cheng Yiwu Yuan Zhenyu Xing Fei Fan Xianghui Wang shengjiang chang Institute of Modern Optics Nankai UniversityTianjin 300350China Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology Tianjin 300350China Tianjin Key Laboratory of Optoelectronic Sensor and Sensing Network Technology Tianjin 300350China

The powerful wavefront manipulation capability of metasurfaces originates from their subwavelength or deep subwavelength elements with designable optical responses, especially phase responses. However, they usually suffer from performance degradation as the spatial phase gradient is large. To solve this issue, we propose an accurate and efficient nonlocal diffraction engineering mechanism to tailor an arbitrary large-gradient wavefront utilizing superwavelength-scale elements. The fast-varying phase profile is cut into segments according to 2π zones rather than subwavelength discretization. Each phase segment is accurately implemented by precisely tailoring the diffraction pattern of the element, where diffraction angles, efficiencies, and phases are controlled simultaneously. As proof of the concept, high numerical aperture cylindrical metalenses are designed using this method and experimentally validated at the terahertz band. The cylindrical metalens is further extended to a fullspace metalens, which enables high-quality subwavelength imaging with resolved details of 0.65λ. The proposed mechanism offers an efficient way to capture the fast-varying wavefront using relatively coarse geometries with new physical insights.

关键词： phase gradient local

Research progress on short-term mechanical properties of FRP bars and FRP-reinforced concrete beams

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Journal of Traffic and Transportation Engineering(English Edition) 2024年第2期11卷 245-270页

作者： Lili Xing shengjiang Sun Kuihua Mei Yiping Guo Zhenhong Yang School of Highway Chang'an UniversityXi'an 710064China

Fiber-reinforced polymer(FRP)bars have been increasingly recognized in the field of civil engineering due to their advantages of light weight,high strength and excellent *** bars can replace steel bars in concrete beams and effectively improve the durability of *** this paper,the literature relevant to the short-term mechanical properties of FRP bars and FRP-reinforced concrete beams was reviewed based on previous studies and practical engineering ***,the mechanical properties of FRP bars were *** types of fibers or steel and fibers can be combined to obtain hybrid fiber-reinforced polymer(HFRP)or steel-fiber composite bars(SFCB)with excellent mechanical performance,*** bond performance and bond-slip model between FRP bars and concrete were *** common bond-slip models were usually used to study the bond performance between carbon fiber-reinforced polymer(CFRP)bars or glass fiber-reinforced polymer(GFRP)bars and concrete,but changing the type of FRP bars will lead to larger ***,the experimental studies,theoretical calculation methods and finite element simulation methods of flexural/shear behavior of FRP-reinforced concrete beams were ***,their applications in practical engineering were discussed and the prospects of further research were *** is pointed out that FRP-reinforced ultra-high performance concrete(UHPC)beams,FRP-reinforced geopolymer concrete(GPC)beams,engineered cementitious composites(ECC)-FRP-reinforced concrete beams,prestressed FRP-reinforced concrete beams and steel/FRP hybrid-reinforced concrete beams can effectively improve the deformation resistance and poor ductility of pure FRP-reinforced concrete beams.

关键词： FRP bars Bond performance Flexural/shear behavior Civil engineering

Tunable magneto-optical polarization device for terahertz waves based on InSb and its plasmonic structure

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Photonics Research 2019年第3期7卷 325-331页

作者： QIANYI MU FEI FAN SAI CHEN SHITONG XU CHUANZHONG XIONG XIN ZHANG XIANGHUI WANG shengjiang chang Institute of Modern Optics Nankai University Tianjin Key Laboratory of Optoelectronic Sensor and Sensing Network Technology State Key Laboratory of Applied Optics Changchun Institute of Optics Fine Mechanics and Physics Chinese Academy of Sciences Nanophotonics and Optoelectronics Research Center Qian Xuesen Laboratory of Space Technology China Academy of Space Technology

The nonreciprocal circular dichroism and Faraday rotation effect for terahertz(THz) waves in longitudinally magnetized InSb were investigated by theoretical and experimental studies in the THz regime, which indicated its ability for a THz circularly polarized isolator, THz circular polarizer, tunable polarization converter, and polarization modulator by manipulation of different magnetic fields. Furthermore, we demonstrated the InSb plasmonics based on its magneto-optical effects combined with artificial microstructure. We found the magnetooptical enhancement mechanisms in this magneto-plasmonic structure, achieving broadband near-perfect orthogonal linear polarization conversion modulated by the weak magnetic field in an experiment with an extinction ratio of 33 dB. Moreover, the magneto-optical modulation with an amplitude modulation depth of 95.8% can be achieved by this device under a weak magnetic field of 150 mT. InSb and its magneto-plasmonic device have broad potential for a THz isolator, magneto-optical modulator, and polarization convertor in THz application systems.

关键词： Tunable magneto-optical polarization device terahertz waves InSb

Arbitrary terahertz chirality construction and flexible manipulation enabled by anisotropic liquid crystal coupled chiral metasurfaces

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Photonics Research 2023年第11期11卷 1880-1891页

作者： XINHAO JIANG YUNYUN JI FEI FAN SONGLIN JIANG ZHIYU TAN HUIJUN ZHAO JIERONG CHENG shengjiang chang Institute of Modern Optics Nankai UniversityTianjin 300350China Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology Tianjin 300350China Tianjin Key Laboratory of Optoelectronic Sensor and Sensing Network Technology Tianjin 300350China

Chiral metasurfaces integrated with active materials can dynamically control the chirality of electromagnetic waves,making them highly significant in physics,chemistry,and ***,we theoretically proposed a general and feasible design scheme to develop a chiral metadevice based on a bilayer anisotropic metasurface and a monolayer liquid crystal(LC),which can construct and flexibly manipulate arbitrary terahertz(THz)*** the twist angle between the anisotropic axes of two metasurfacesθis not 0°,the spatial mirror symmetry of the chiral metadevice is broken,resulting in a strong THz chiral *** addition,the introduction of anisotropic LCs not only enhances the chiral response of the metadevice but also induces the flipping modulation and frequency tunability of the *** importantly,by optimizing theθ,we can flexibly design the arbitrary chiral response and the operating frequency of chirality,thereby promoting the emergence of various chiral manipulation *** experimental results show that the maximum circular dichroism can reach-33 d B at 0.94 THz and flip to 28 d B at 0.69 THz by rotating the LC optical axis from the x to y axis,with the maximum operating frequency tunable range of~120 *** expect this design strategy can create new possibilities for the advancement of active THz chiral devices and their applications,including chiral spectroscopy,molecular recognition,biosensing,and fingerprint detection.

关键词： chiral anisotropic crystal

Sidelobe suppression and axial resolution enhancement in 4pi microscopy with higher-order radially polarized Laguerre–Gaussian beams using subtractive imaging

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Chinese Optics Letters 2019年第12期17卷 38-43页

作者： Zhiyuan Gu Xianghui Wang Jianxin Wang Fei Fan shengjiang chang Institute of Modern Optics Tianjin Key Laboratory of Optoelectronic Sensor and Sensing Network TechnologyNankai UniversityTianjin 300350China

Subtractive imaging is used to suppress the axial sidelobes and improve the axial resolution of 4 pi microscopy with a higher-order radially polarized(RP)Laguerre–Gaussian(LG)beam.A solid-shaped point spread function(PSF)and a doughnut-shaped PSF with a dark spot along the optical axis are generated by tightly focusing a higher-order RP-LG beam and a modulated circularly polarized beam,*** subtracting the two images obtained with those two different PSFs,the axial sidelobes of the subtracted PSF are reduced from 37% to about 10% of the main lobe,and the axial resolution is increased from 0.21λ to 0.15λ.

关键词： polarized axial radial

Liquid crystal integrated metamaterial for multi-band terahertz linear polarization conversion

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Chinese Optics Letters 2021年第9期19卷 127-132页

作者： Shitong Xu Fei Fan Hongzhong Cao Yinghua Wang shengjiang chang Shandong Provincial Key Laboratory of Laser Polarization and Information Technology Department of PhysicsSchool of Physics and EngineeringQufu Normal UniversityQufu 273165China Institute of Modern Optics Tianjin Key Laboratory of Micro-Scale Optical Information Science and TechnologyNankai UniversityTianjin 300350China Tianjin Key Laboratory of Optoelectronic Sensor and Sensing Network Technology Tianjin 300350China

We experimentally investigate the linear polarization conversion for terahertz(THz)waves in liquid crystal(LC)integrated metamaterials,which consist of an LC layer sandwiched by two orthogonally arranged sub-wavelength metal gratings.A Fabry-Perot-like cavity is well constructed by the front and rear gratings,and it shows a strong local resonance mechanism,which greatly enhances the polarization conversion *** importantly,the Fabry-Perot-like resonance can be actively tuned by modulating the refractive index of the middle LC layer under the external *** a result,the integrated metamaterial achieves multi-band tunable linear polarization conversion.

关键词： terahertz liquid crystals metamaterial polarization conversion

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基于异步卷积分解与分流结构的单阶段检测器

北京航空航天大学学报 2019年第10期45卷 2089-2098页

作者：赵蓬辉孟春宁常胜江南开大学电子信息与光学工程学院现代光学研究所天津300350 中国人民武装警察部队海警学院电子技术系宁波315801

目标检测网络SSD的多层回归特征图存在各层回归计算之间相对独立的问题,且基于SSD改进的系列算法在提高检测精度的同时难以兼顾实时性。针对上述问题,提出一种基于异步卷积分解与分流(shunt)结构的单阶段目标检测器。基于异步卷积分解... 详细信息

目标检测网络SSD的多层回归特征图存在各层回归计算之间相对独立的问题,且基于SSD改进的系列算法在提高检测精度的同时难以兼顾实时性。针对上述问题,提出一种基于异步卷积分解与分流(shunt)结构的单阶段目标检测器。基于异步卷积分解算法设计了一种shunt结构,交错连接多层特征图,增强了回归计算之间的统一性与协调性。优化了原有高层主流结构,在主流结构与shunt结构中分别用最大池化和异步卷积分解2种不同的方式对特征图大小进行降维,保留空间相关信息的同时提高了特征的多样性。实验结果表明,将VOC2007trainval和VOC2012trainval中的图片统一缩小至300像素×300像素进行训练,提出的目标检测器在VOC2007test上进行检测时的平均精度均值可达到80. 5%,检测速度超过30帧/s。

关键词：目标检测卷积神经网络异步卷积分解分流结构结构优化