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Chinese Physics Letters 2024年第4期41卷 45-50页

作者：蓝志强李章顺徐浩然刘凡金钻明彭滟朱亦鸣 terahertz Technology Innovation research Institute Terahertz Spectrum and Imaging Technology Cooperative Innovation CenterShanghai Key Lab of Modern Optical SystemUniversity of Shanghai for Science and TechnologyShanghai 200093China

Using THz emission spectroscopy,we investigate the elementary spin dynamics in ferromagnetic single-layer Fe on a sub-picosecond *** demonstrate that THz radiation changes its polarity with reversal of the magnetization applied by the external magnetic *** addition,it is found that the sign of THz polarity excited from different sides is defined by the thickness of the Fe layer and Fe/dielectric *** on the thickness and symmetry dependences of THz emission,we experimentally distinguish between the two major contributions:ultrafast demagnetization and the anomalous Hall *** experimental results not only enrich understanding of THz electromagnetic generation induced by femtosecond laser pulses but also provide a practical way to access laser-induced ultrafast spin dynamics in magnetic structures.

关键词： magnetic magnetization polarity

Electron-beam-driven anomalous Doppler effects in Smith–Purcell radiation

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Photonics research 2024年第1期12卷 78-84页

作者： XIAOQIUYAN ZHANG TIANYU ZHANG ZHUOCHENG ZHANG XINGXING XU DIWEI LIU ZHAOYUN DUAN YANYU WEI YUBIN GONG LIANG JIE WONG MIN HU terahertz research center School of Electronic Science and EngineeringUniversity of Electronic Science and Technology of ChinaChengdu 610054China Key Laboratory of terahertz Technology Ministry of EducationChengdu 610054China School of Electrical and Electronic Engineering Nanyang Technological UniversitySingapore 639798Singapore

The interaction between electrons and matter is an effective means of light emission,through mechanisms including Cherenkov radiation and Smith–Purcell radiation(SPR).In this study,we show that the superlight inverse Doppler effects can be realized in reverse Smith–Purcell radiation excited by a free electron beam with a homogeneous *** particular,we find that two types of anomalous SPR exist in the homogenous substrate:special SPR and reverse *** results reveal that the electron velocity can be tuned to simultaneously excite different combinations of normal SPR,special SPR,and reverse *** proposed manifold light radiation mechanism can offer greater versatility in controlling and shaping SPR.

关键词： anomalous beam Electron

Highly sensitive flexible strain sensor based on the two-dimensional semiconductor tellurium with a negative gauge factor

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Science China(Information Sciences) 2024年第7期67卷 295-304页

作者： Jiarui HE Yusong QU Shengyao CHEN Cong WANG Lena DU Xiaoshan DU Yuanyuan ZHENG Guozhong ZHAO He TIAN College of Mathematics and Physics Beijing University of Chemical Technology School of Integrated Circuits Tsinghua University Beijing China & The Beijing National Research Center for Information Science and Technology (BNRist)Tsinghua University CAS center for Excellence in Nanoscience National Center for Nanoscience and Technology &University of Chinese Academy of Sciences Beijing Key Lab of terahertz Spectroscopy and Imaging Key Lab of Terahertz OptoelectronicsMinistry of Education Department of Physics Capital Normal University

research on flexible strain sensors has advanced rapidly in recent years, with particular attention being devoted to two-dimensional(2D) semiconductor materials owing to their exceptional mechanical and electrical properties that are conducive to sophisticated sensing performance. However, resistive strain sensors based on 2D semiconductor materials typically exhibit positive gauge factors(GF), while materials for strain sensors with a negative GF remain elusive. We have identified a trend of reduction in the band gap of the emerging 2D semiconductor material tellurium(Te) under strain in simulations reported in past research,and have observed a negative GF in the Te-based strain sensor. In this study, we combined Te with a flexible polyethylene terephthalate(PET) substrate to manufacture a flexible strain sensor with a significantly negative GF. The results of tests revealed that the Te-based strain sensor achieved an impressive maximum sensitivity of-139.7 within a small range of bending-induced strain(< 1%). Furthermore, it exhibited excellent linearity and good cyclic stability, and was successfully applied to monitor limb movements. The work here verifies the significant potential for the use of Te-based strain sensors in next-generation flexible electronics.

关键词： 2D semiconductor materials 2D tellurium flexibleelectronics strain sensors negative gauge factor high sensitivity

Advancing large-scale thin-film PPLN nonlinear photonics with segmented tunable micro-heaters

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Photonics research 2024年第8期12卷 1703-1708页

作者： XIAOTING LI HAOCHUAN LI ZHENZHENG WANG ZHAOXI CHEN FEI MA KE ZHANG WENZHAO SUN CHENG WANG Department of Electrical Engineering City University of Hong Kong School of Physics Sun Yat-sen University City University of Hong Kong (Dongguan) center of Information and Communication Technology City University of Hong Kong Shenzhen Research Institute State Key Laboratory of terahertz and Millimeter Waves City University of Hong Kong

Thin-film periodically poled lithium niobate (TF-PPLN) devices have recently gained prominence for efficient wavelength conversion processes in both classical and quantum applications. However, the patterning and poling of TF-PPLN devices today are mostly performed at chip scales, presenting a significant bottleneck for future largescale nonlinear photonic systems that require the integration of multiple nonlinear components with consistent performance and low cost. Here, we take a pivotal step towards this goal by developing a wafer-scale TF-PPLN nonlinear photonic platform, leveraging ultraviolet stepper lithography and an automated poling process. To address the inhomogeneous broadening of the quasi-phase matching(QPM) spectrum induced by film thickness variations across the wafer, we propose and demonstrate segmented thermal optic tuning modules that can precisely adjust and align the QPM peak wavelengths in each section. Using the segmented micro-heaters, we show the successful realignment of inhomogeneously broadened multi-peak QPM spectra with up to 57% enhancement of conversion efficiency. We achieve a high normalized conversion efficiency of 3802% W-1cm-2in a 6 mm long PPLN waveguide, recovering 84% of the theoretically predicted efficiency in this device. The advanced fabrication techniques and segmented tuning architectures presented herein pave the way for wafer-scale integration of complex functional nonlinear photonic circuits with applications in quantum information processing, precision sensing and metrology, and low-noise-figure optical signal amplification.

关键词： Lithium niobate Optical amplifiers Optical parametric oscillators Optical signals Precision metrology Wavelength conversion

Effects of water molecules on luminescence in europium and terbium coordination polymers with p-fluorobenzoic acid as ligand

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Journal of Rare Earths 2024年第7期42卷 1258-1264,I0003页

作者： Xiaoqi Zhao Puyan Hao Yami Ling Mengzhen Jia Rui Zhu Jiawen Liu Qiang Xu Jianhong Zhou Collaborative Innovation center of Rare-Earth Optical Functional Materials and Devices Development Baoji Key Laboratory of Micro-Nano Optoelectronics and Terahertz TechnologySchool of Physics and Opto-Electronic TechnologyBaoji University of Arts and SciencesBaoji721016China

Our previous experimental observations show that the crystal structure of lanthanide luminescent complexes synthesized in aqueous solution usually contains a large number of coordination water molecules or free water *** order to probe the influence of water molecules on luminescent processes of lanthanide complexes,the photoluminescence properties of Ln-FBA(Ln=Eu and Tb,FBA=p-fluorobenzoic acid)coordination polymers at different ambient temperatures,in different solvents and aqueous DMSO solutions with different volume concentrations were systematically *** experiment results show that the presence of water molecules can promote the energy transfer from FBA ligand to Ln3+,at the same time,can cause luminescent non-radiation quenching of lanthanide *** addition,the variation of emission intensity ratio of 615 nm/591 nm peaks of Eu^(3+)with increasing the volume concentration of H_(2)O can be potentially used for the quantitatively detection of water traces in organic *** order to suppress the non-radiation quenching caused by the water molecules,Ln-FBA(Ln=Eu and Tb)coordination polymers were embedded into the PVP matrix to prepare Ln-FBA@PVP hybrid *** photoluminescence investigation indicates that PVP can not only block the quenching effect of water molecules on luminescence,but also effectively sensitize Eu^(3+)and Tb^(3+)*** experimental conclusions are useful for probing the influence of water molecules on luminescent processes of lanthanide complexes,quantitatively detecting water traces in organic solvents and enhancing the photoluminescence intensity in lanthanide complexes.

关键词： Lanthanide complexes Photoluminescence Luminescent quenching Rare earths

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Synthesis of boron nitride nanorod and its performance as a metalfree catalyst for oxidative desulfurization of diesel fuel

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Chinese Journal of Chemical Engineering 2024年第4期68卷 120-132页

作者： Tanaz Ghanadi Gholamreza Moradi Alimorad Rashidi Catalyst research center Faculty of Chemical and Petroleum EngineeringRazi UniversityKermanshahIran Nanotechnology research center Research Institute of Petroleum Industry(RIPI)TehranIran

In order to reduce the sulfur compounds in diesel fuel,boron nitride(BN)has been used as a novel metal-free catalyst in the present *** nanocatalyst was synthesized via template-free approach followed by heating treatment at 900℃ in nitrogen atmosphere that the characteristics of the sample were identified by the X-ray diffraction,Fourier-transform infrared spectroscopy,Raman spectroscopy,field emission scanning electron microscopy,transmission electron microscopy,atomic force microscopy,and N2 adsorption-desorption *** results of structural and morphological analysis represented that BN has been successfully *** efficacy of the main operating parameters on the process was studied by using response surface methodology based on the Box-Behnken design *** prepared catalyst showed high efficiency in oxidative desulfurization of diesel fuel with initial sulfur content of 8040 mg·kg^(-1)*** statistical analysis,a significant quadratic model was obtained to predict the sulfur removal as a function of efficient *** maximum efficiency of 72.4%was achieved under optimized conditions at oxidant/sulfur molar ratio of 10.2,temperature of 71℃,reaction time of 113 min,and catalyst dosage of 0.36 ***,the reusability of the BN was studied,and the result showed little reduction in activity of the catalyst after 10 times ***,a plausible mechanism was proposed for oxidation of sulfur compounds on the surface of the *** present study shows that BN materials can be selected as promising metal-free catalysts for desulfurization process.

关键词： Desulfurization Boron nitride(BN)nanostructure Experimental design BoxeBehnken

The stress-thermal equivalence “memory effect” in glass materials

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Science China(Physics,Mechanics & Astronomy) 2024年第10期Mechanics & Astronomy) .卷 179-180页

作者： Pengfei Guan Beijing Computational Science research center

Glass materials, including metallic, organic, and silicate glasses, are crucial in various engineering applications due to their unique disordered atomic packing structures. However,these materials suffer from stress decay under constant strain, known as stress relaxation, which negatively impacts their load-bearing capacity, stability, and service life.

关键词： glasses glass stress

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Comparative analysis between single-train passing and double-train intersection in a tunnel

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2024年第5期25卷 429-442页

作者： Jianming DU Qian FANG Xuan ZHANG Hualao WANG Bridge and Tunnel research center Research Institute of Highway Ministry of TransportBeijing 100088China Tunnel and Underground Engineering research center of Ministry of Education Beijing Jiaotong UniversityBeijing 00044China

Aerodynamic pressure significantly impacts the scientific evaluation of tunnel service *** aerodynamic pressure of two trains running in a double-track tunnel is considerably more complicated than that of a single *** used the numerical method to investigate the difference in aerodynamic pressure between a single train and two trains running in a double-track ***,the numerical method was verified by comparing the results of numerical simulation and on-site ***,the characteristics of aerodynamic pressure were ***,the influence of various train-tunnel factors on the characteristics of aerodynamic pressure was *** results show that the aerodynamic pressure variation can be divided into stage I:irregular pressure fluctuations before the train tail leaves the tunnel exit,and stage II:periodic pressure declines after the train tail leaves the tunnel *** addition,the aerodynamic pressure simultaneously jumps positively or drops negatively for a single train or two trains running in double-track tunnel *** pressure amplitude in the two-train case is higher than that for a single *** maximum positive peak pressure difference(P_(STP))and maximum negative peak pressure difference(P_(STN))increase as train speed rises to the power from 2.256 to 2.930 in stage *** P_(STP) and P_(STN) first increase and then decrease with the increase of tunnel length in stage *** P_(STP) and P_(STN) increase as the blockage ratio rises to the power from 2.032 to 2.798 in stages I and II.

关键词： Railway tunnel Aerodynamic effect Pressure characteristic Train speed Tunnel length Blockage ratio

Comprehensive study of the ultrafast photoexcited carrier dynamics in Sb_(2)Te_(3)–GeTe superlattices

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Chinese Physics B 2024年第7期33卷 381-387页

作者：叶之江金钻明蒋叶昕卢琦贾梦辉钱冬黄夏敏李舟彭滟朱亦鸣 terahertz Technology Innovation research Institute Terahertz Spectrum and Imaging Technology Cooperative Innovation CenterShanghai Key Laboratory of Modern Optical SystemUniversity of Shanghai for Science and TechnologyShanghai 200093China Shanghai Institute of Intelligent Science and Technology Tongji UniversityShanghai 200092China Key Laboratory of Artificial Structures and Quantum Control(Ministry of Education) Shenyang National Laboratory for Materials ScienceSchool of Physics and AstronomyShanghai Jiao Tong UniversityShanghai 200240China Tsung-Dao Lee Institute Shanghai Jiao Tong UniversityShanghai 200240China State Key Laboratory of Precision Spectroscopy East China Normal UniversityShanghai 200062China GBA Branch of Aerospace Information research Institute Chinese Academy of SciencesGuangzhou 510700China Guangdong Provincial Key Laboratory of terahertz Quantum Electromagnetics Guangzhou 510700China University of Chinese Academy of Sciences Beijing 100039China

Chalcogenide superlattices Sb_(2)Te_(3)-GeTe is a candidate for interfacial phase-change memory(iPCM) data storage *** employing terahertz emission spectroscopy and the transient reflectance spectroscopy together,we investigate the ultrafast photoexcited carrier dynamics and current transients in Sb_(2)Te_(3)-GeTe *** orientation and excitation polarization dependences of the THz emission confirm that ultrafast thermo-electric,shift and injection currents contribute to the THz generation in Sb_(2)Te_(3)-GeTe *** decreasing the thickness and increasing the number of GeTe and Sb_(2)Te_(3) layer,the interlayer coupling can be enhanced,which significantly reduces the contribution from circular photo-galvanic effect(CPGE).A photo-induced bleaching in the transient reflectance spectroscopy probed in the range of~1100 nm to~1400 nm further demonstrates a gapped state resulting from the interlayer *** demonstrates play an important role in the development of iPCM-based high-speed optoelectronic devices.

关键词： Sb_(2)Te_(3)/GeTe superlattices ultrafast carrier dynamics interfacial phase change memory THz emission spectroscopy transient reflectance spectroscopy

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Photonic crystal-connected bidirectional micro-ring resonator array for duplex mode and wavelength channel(de) multiplexing

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Photonics research 2024年第8期12卷 1802-1812页

作者： ZHIWEI GUAN CHAOFENG WANG CHUANGXIN XIE HAISHENG WU JUNMIN LIU HUAPENG YE DIANYUAN FAN JIANGNAN XIAO SHUQING CHEN International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology Institute of Microscale OptoelectronicsShenzhen University College of Physics and Engineering Technology Minzu Normal University of Xingyi College of New Materials and New Energies Shenzhen Technology University Guangdong Provincial Key Laboratory of Optical Information Materials and Technology and Institute of Electronic Paper Displays South China Academy of Advanced OptoelectronicsSouth China Normal University terahertz Technology Innovation research Institute Shanghai Key Laboratory of Modern Optical SystemTerahertz Science Cooperative Innovation CenterSchool of Optical-Electrical Computer EngineeringUniversity of Shanghai for Science and Technology

The progress of on-chip optical communication relies on integrated multi-dimensional mode（de）multiplexers to enhance communication capacity and establish comprehensive networks. However, existing multi-dimensional（de）multiplexers, involving modes and wavelengths, face limitations due to their reliance on single-directional total internal reflection and multi-level mode conversion based on directional coupling principles. These constraints restrict their potential for full-duplex functionality and highly integrated communication. We solve these problems by introducing a photonic-like crystal-connected bidirectional micro-ring resonator array（PBMRA）and apply it to duplex mode-wavelength multiplexing communication. The directional independence of total internal reflection and the cumulative effect of the subwavelength-scale pillar within the single-level photonic crystal enable bidirectional mode and wavelength multiplexed signals to transmit among multi-pair nodes without interference, improving on-chip integration in single-level mode conversion. As a proof of concept, we fabricated a nine-channel bidirectional multi-dimensional（de）multiplexer, featuring three wavelengths and three TE modes, compactly housed within a footprint of 80 μm × 80 μm, which efficiently transmits QPSK-OFDM signals at a rate of 216 Gbit/s, achieving a bit error rate lower than 10-4. Leveraging the co-ring transmission characteristic and the orthogonality of the mode-wavelength channel, this（de）multiplexer also enables a doubling of communication capacity using two physical transmission channels.

关键词： Mode conversion Mode division multiplexing Optical networks Phase modulation Total internal reflection Wavelength division multiplexing