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Unveiling of Terahertz Emission from Ultrafast Demagnetization and the Anomalous Hall Effect in a Single Ferromagnetic Film

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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

Single-step-etched ultra-compact metamaterial grating coupler enabled by a hierarchical inverse design approach

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Science China(Physics,Mechanics & Astronomy) 2024年第2期67卷 119-126页

作者： Qiao Wang Ruiqi Luo Nan Liu Maojing Hou Bo Xiong Guandong Liu Wei Ma Intelligent Network research Institute Zhejiang LabHangzhou 311100China State Key Laboratory of Modern optical Instrumentation College of Information Science and Electronic EngineeringZhejiang UniversityHangzhou 310027China

With the concept of metamaterials introduced into integrated photonics,subwavelength structures have gained popularity for their ability to create devices with ultra-compact size,high performance,and versatile ***,traditional metamaterial design methods are usually based on empirical templates and physical approximations,lacking the ability to design free-form metamaterial structures and optimize entire devices *** this work,we propose a hierarchical inverse design approach that combines a conventional effective refractive index based metamaterial structures design with a follow-up global topology *** empirical metamaterial grating coupler design based on effective refractive index engineering faces inaccurate index extraction and insufficient approximation of wavevector matching conditions,which deteriorates coupling efficiency,especially for fully-etched devices with the decreased tapering ***,a subsequent overall topology optimization step can well compensate for the negative effect of the shrinking device footprint to increase the efficiency of the metamaterial grating *** demonstrate a 23μm×10μm ultra-compact metamaterial grating coupler with single-stepetched to couple light between a fiber and a 500 nm single-mode silicon waveguide in the *** measurement shows an insertion loss of 3.17 dB and a 3 dB bandwidth of 77 nm,making it the smallest footprint device ever reported.

关键词： waveguide hierarchical inverse

Silicon photonic spectrometer with multiple customized wavelength bands

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Photonics research 2024年第5期12卷 1016-1023页

作者： LONG ZHANG XIAOLIN YI DAJIAN LIU SHIHAN HONG GAOPENG WANG HENGZHEN CAO YAOCHENG SHI DAOXIN DAI State Key Laboratory for Modern optical Instrumentation Center for Optical&Electromagnetic ResearchCollege of Optical Science and EngineeringInternational Research Center for Advanced PhotonicsZhejiang UniversityZjingang CampusHangzhou 310058China Intelligent Optics and Photonics research Center Jiaxing Research InstituteZhejiang UniversityJiaxing 314000China Ningbo research Institute Zhejiang UniversityNingbo 315100China

A silicon photonic spectrometer with multiple customized wavelength bands is developed by introducing multiple channels of wideband optical filters based on multimode waveguide gratings(MWGs)for pre-filtering and the corresponding thermally tunable narrowband filter for high *** these multiple customized wavelength bands,the central wavelengths,bandwidths,and resolutions are designed flexibly as desired,so that the system is simplified and the footprint is minimized for several practical applications(e.g.,gas sensing).A customized silicon photonic spectrometer is designed and demonstrated experimentally with four wavelength bands centered around1310 nm,1560 nm,1570 nm,and 1930 nm,which is,to the best of our knowledge,the first on-chip spectrometer available for sensing multiple gas components like HF,CO,H_(2)S,and CO_(2).The spectral resolutions of the four wavelength bands are 0.11 nm,0.08 nm,0.08 nm,and 0.37 nm,*** a customized silicon photonic spectrometer shows great potential for various applications,including gas monitors,wearable biosensors,and portable spectral-domain optical coherence tomography.

关键词： waveguide bands multiple

MLSE-assisted decision feedback equalizer for error-propagation suppression in high-speed IM-DD transmission systems

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Chinese Optics Letters 2024年第5期22卷 36-40页

作者：周家豪张静赵雪王芮李劲江胡少华张倩武杨奇许渤邱昆 Key Laboratory of optical Fiber Sensing and Communication University of Electronic Science and Technology of ChinaChengdu 611731China Key Laboratory of Specialty Fiber Optics and optical Access Networks Shanghai UniversityShanghai 200444China School of optical and Electronic Information Huazhong University of Science and TechnologyWuhan 430074China

We propose a trellis-compressed maximum likelihood sequence estimation(TC-MLSE)-assisted sliding-block decision feedback equalizer(DFE)to suppress the error propagation resulting from the DFE in high-speed *** use an out-ofrange detector to detect the end of burst errors from the DFE and activate the optional TC-MLSE to correct burst *** conduct experiments to transmit a 201-Gbit/s PAM-8 *** results show that the proposed method achieves a bit error rate of 3.65×10^(-3),which is close to that of *** optional MLSE is only activated when needed and processes 11.4%of the total ***,the proposed method compresses the maximum length of burst errors from 19 to 5.

关键词： intensity modulation direct detection sliding-block decision feedback equalizer error propagation maximum likelihood sequence estimation out-of-range detector

Deterministic relation between thermalphonon dressings and a non-Hermitian multi-Fano interferences router in iondoped microcrystals

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Chip 2024年第1期3卷 24-34页

作者： Huanrong Fan Faizan Raza Anas Mujahid Peng Li Yafen Wang Haitian Tang Muhammad Usman Bo Li Changbiao Li Yanpeng Zhang Key Laboratory for Physical Electronics and Devices of the Ministry of Education&Shaanxi Key Lab of Information Photonic Technique Xi’an Jiaotong UniversityXi’an 710049China Center for Regenerative and Reconstructive Medicine Med-X InstituteThe First Affiliated Hospital of Xi’an Jiaotong UniversityXi’an 710061China State Key Lab of Modern optical Instrumentation Centre for Optical and Electromagnetic ResearchCollege of Optical Science and EngineeringInternational Research Center for Advanced PhotonicsZhejiang UniversityHangzhou 310058China

The multi-Fano interference,which is obtained through the simultaneous acquisition of bright and dark states in different phase transitions of Eu3+:BiPO4(7:1,6:1,1:1,and 0.5:1)and Eu3+:NaYF4(1:1/4)crystals,were reported in this *** spontaneous four-wave mixing and multidressed fluorescence(multiorder)were adopted to optimize the strong photon–phonon nested dressing effect,which results in more obvious multi-Fano ***,the multi-Fano is produced through interference in continuous and multibound ***,five multi-Fano dips are originated from the nested five dressings(one photon and four phonons)under symmetrical splitting of 7F1 energy *** is found that the pure H-phase(0.5:1)sample exhibits the strongest photon–phonon dressed effect(five Fano dips).Further,high-order non-Hermitian exceptional points in multi-Fano interference were investigated by adjusting the ratio of Rabi frequency to dephase rate through nested photon and phonon *** experimental results are validated by theoretical simulations,which may be applied to designing optoelectronic devices such as non-Hermitian multi-Fano interferences(multichannel)router.

关键词： Multi-Fano interferences Thermal-phonon dressings Non-Hermitian Router

Advancing brain-inspired computing with hybrid neural networks

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National Science Review 2024年第5期11卷 56-71页

作者： Faqiang Liu Hao Zheng Songchen Ma Weihao Zhang Xue Liu Yansong Chua Luping Shi Rong Zhao Center for Brain-Inspired Computing research Optical Memory National Engineering Research CenterTsinghua University-China Electronics Technology HIK Group Co.Joint Research Center for Brain-inspired ComputingIDGMc Govern Institute for Brain Research Department of Precision Instrument Tsinghua University Neuromorphic Computing Laboratory China Nanhu Academy of Electronics and Information Technology

Brain-inspired computing, drawing inspiration from the fundamental structure and information-processing mechanisms of the human brain, has gained significant momentum in recent years. It has emerged as a research paradigm centered on brain–computer dual-driven and multi-network integration. One noteworthy instance of this paradigm is the hybrid neural network(HNN), which integrates computer-science-oriented artificial neural networks(ANNs) with neuroscience-oriented spiking neural networks(SNNs). HNNs exhibit distinct advantages in various intelligent tasks, including perception, cognition and learning. This paper presents a comprehensive review of HNNs with an emphasis on their origin, concepts, biological perspective, construction framework and supporting systems. Furthermore, insights and suggestions for potential research directions are provided aiming to propel the advancement of the HNN paradigm.

关键词： brain-inspired computing hybrid neural network dual-brain driven multi-network integration neuromorphic system

Inversely engineered metasurfaces for independent manipulation of transmitted and reflected light fields

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Science China(Physics,Mechanics & Astronomy) 2024年第7期67卷 97-106页

作者： Yongjian Liu Yu Luo Fei Zhang Mingbo Pu Hanlin Bao Mingfeng Xu Yinghui Guo Lanting Li Xiong Li Xiaoliang Ma Xiangang Luo National Key Laboratory of optical Field Manipulation Science and Technology Chinese Academy of SciencesChengdu 610209China State Key Laboratory of optical Technologies on Nano-Fabrication and Micro-Engineering Institute of Optics and ElectronicsChinese Academy of SciencesChengdu 610209China College of Materials Science and Opto-Electronic Technology University of Chinese Academy of SciencesBeijing 100049China research Center on Vector optical Fields Institute of Optics and ElectronicsChinese Academy of SciencesChengdu 610209China Tianfu Xinglong Lake Laboratory Chengdu 610299China

Independent manipulation of transmitted and reflected light fields is a key technology for the realization of multifunctional optical applications,which can be implemented based on multilayered plasmonic or supercell subwavelength ***,the former is not suitable for the optical bands,while the latter is insufficient in generating large phase ***,an adjoint-optimization-based inverse design methodology is proposed,which utilizes the polarization-selective local interference between individual meta-atoms and enables monolayer dielectric metasurfaces to decouple the wavefront of transmitted and reflected optical ***,this methodology serves to mitigate the aperiodic electromagnetic crosstalk inherent between adjacent meta-atoms,consequently leading to a significant enhancement in the performance of *** analyzed the physical mechanism of adjoint optimization and proposed the concept of phase factors,highlighting their importance in the rapid inverse design of meta-devices—an aspect often overlooked in previous *** demonstrate the feasibility and robustness of our method,we optimize monolayer metasurfaces with different initial *** devices efficiently focus and deflect x-linearly and y-linearly polarized incident light in transmission and reflection spaces,***,this methodology holds immense potential for designing multifunctional,high-performing metasurfaces that meet multiple constraints,opening up broad prospects for applications.

关键词： full-space metasurfaces adjoint optimization inverse design

Stability-enhanced RF signal transmission over long fiber-optic links

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Chinese Optics Letters 2024年第5期22卷 131-136页

作者：尹知谦郑满航张川博管世健周昕刘奕彤刚泽宇聂佳强张云山朱兴邦方涛陈向飞 Engineering research Center of Precision Photonics Integration and System Application Ministry of Education&Key Laboratory of Intelligent Optical Sensing and ManipulationMinistry of Education&National Laboratory of Solid State Microstructures&College of Engineering and Applied Sciences&Institute of Optical Communication Engineering&Nanjing University-Tongding Joint Lab for Large-scale Photonic Integrated CircuitsNanjing UniversityNanjing 210023China College of Electronics and optical Engineering and College of Flexible Electronics(Future Technology) Nanjing University of Posts and TelecommunicationsNanjing 210023China The 41st research Institute of China Electronics Technology Group Corp Qingdao 266000China

We propose a method for optimizing the phase stability of microwave signal transmission over long ***,the design of the photon link was modified to reduce the radio frequency(RF)signal’s baseline noise and increase ***,a low-noise driver circuit was developed for a two-section distributed feedback(DFB)laser designed using reconstruction equivalent chirp(REC)technology to create an ultra-stable laser,and its performance was characterized through linewidth *** results indicate that the DFB laser achieved narrower linewidth,improving system phase *** an injection current(30 mA)is applied to the reflection section of the two-section DFB laser,the laser linewidth will be narrower(1.38 MHz),further enhancing the system’s phase transmission *** a 1 Hz offset frequency,a residual phase noise of-88.65 dBc/Hz is *** short-term stability with an averaging time of 1 s is 1.60×10^(-14),and the long-term stability over a testing time of 60,000 s is 3.41×10^(-18).Even after incorporating temperature variations,the long-term stability reaches 8.37×10^(-18) at 22 h.

关键词： frequency dissemination two-section distributed feedback laser phase stability

Switching,explosion,and chaos of multi-wavelength soliton states in ultrafast fiber lasers

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Science China(Physics,Mechanics & Astronomy) 2024年第7期67卷 82-90页

作者： Zhi-Zeng Si Yue-Yue Wang Chao-Qing Dai College of optical Mechanical and Electrical EngineeringZhejiang A&F UniversityLin’an 311300China

Because of the complexity and difficulty of realizing a multi-wavelength soliton state,reports on its internal dynamic characteristics are *** this study,the switching and periodic soliton explosion processes of the multi-wavelength soliton state in a negative dispersion passively mode-locked fiber laser are *** generation of the multi-wavelength soliton state undergoes the process of noise,oscillation,and stable mode-locking,and the splitting and annihilation of solitons with different group velocities directly impact the generation and disappearance of three *** and negative dispersion lead to different group velocities of *** presence and displacement of solitons with different group velocities cause soliton collisions,which lead to soliton explosions.A soliton experiences relative phase oscillation,chaos,and oscillation,as well as convergence and separation before and after an *** an increase in parameters related to pump power,single-soliton oscillation,multi-wavelength solitons,and chaos are found in experiments and simulations,proving the relevance and reliability between simulation and experimental *** work promotes the dynamical study of multi-soliton collisions in nonlinear science and the development of chaos theory in multi-comb lasers.

关键词： multi-wavelength fiber laser soliton explosion chaos state switching real-time dynamics