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中国科学:技术科学（英文版）
中国科学:技术科学（英文版）

周光召

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中国科学:技术科学（英文版）/Journal Science China Technological SciencesCSCDCSTPCDEISCI
查看更多>>《中国科学》是中国科学院主办、中国科学杂志社出版的自然科学专业性学术刊物。《中国科学》任务是反映中国自然科学各学科中的最新科研成果，以促进国内外的学术交流。《中国科学》以论文形式报道中国基础研究和应用研究方面具有创造性的、高水平的和有重要意义的科研成果。在国际学术界，《中国科学》作为代表中国最高水平的学术刊物也受到高度重视。国际上最具有权威的检索刊物SCI，多年来一直收录《中国科学》的论文。1999年《中国科学》夺得国家期刊奖的第一名。
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    Preface

    FANG HongHua
    1页
      原文链接:
    • 万方数据
    • 维普

    Ultrafast optical investigation of carrier and spin dynamics in low-dimensional perovskites

    FU JinYueJIANG YingFANG HongHua
    2-18页
    查看更多>>摘要：Low-dimensional perovskite(PVK)materials have attracted significant research interest,because of their quantum-confined effect,tunable band gap structures,and higher stability than that of three-dimensional(3D)PVKs.In semiconductor optoe-lectronic devices,high speed and small size are closely interlinked.The development of high-speed devices requires researchers to fully understand the properties of materials,especially the dynamic processes such as carrier recombination,separation,and transport,which often play a crucial role in the performance of devices.As an indispensable part of dynamic research,spin relaxation is also of great significance in studying the properties of materials and explore possible applications.Lead halide PVK materials have strong spin-orbit coupling(SOC),which provides a basis for information storage and processing by using spin degrees of freedom.Therefore,studying the carrier and spin dynamics of low-dimensional PVKs is an effective way to understand the internal properties of low-dimensional PVKs clearly.This paper summarizes the latest research progress on the ultrafast carrier and spin dynamics in low-dimensional PVKs,to comprehensively understand their carrier and spin behaviors and present an outlook for relevant studies in this area.
      原文链接:
    • 万方数据
    • 维普

    Femtosecond laser-induced periodic surface structures on hard and brittle materials

    ZHAO GuoXuWANG GongLI YunFeiWANG Lei...
    19-36页
    查看更多>>摘要：Hard and brittle materials have high hardness,excellent optical stability,chemical stability,and high thermal stability.Hence,they have huge application potential in various fields,such as optical components,substrate materials,and quantum information,especially under harsh conditions,such as high temperatures and high pressures.Femtosecond laser direct writing technology has greatly promoted the development of femtosecond laser-induced periodic surface structure(Fs-LIPSS or LIPSS by a femtosecond laser)applications of hard and brittle materials due to its high precision,controllability,and three-dimensional processing ability.Thus far,LIPSSs have been widely used in material surface treatment,optoelectronic devices,and micro-mechanics.However,a consensus has not been reached regarding the formation mechanism of LIPSSs on hard and brittle materials.In this paper,three widely accepted LIPSS formation mechanisms are introduced,and the characteristics and ap-plications of LIPSSs on diamonds,silicon,silicon carbide,and fused silica surfaces in recent years are summarized.In addition,the application prospects and challenges of LIPSSs on hard and brittle materials by a femtosecond laser are discussed.
      原文链接:
    • 万方数据
    • 维普

    Process in laser drilling of deep microholes without taper on metal materials

    FAN RunZeMEI XueSongCUI JianLei
    37-59页
    查看更多>>摘要：Deep microhole machining is currently a prominent research area within the aerospace field,encompassing blade film cooling and fuel injection control technologies.However,taper defects in metal materials may lead to performance degradation or even structural damage over a component's lifetime.Trepanning and helical drilling,facilitated by ultrashort pulse lasers,have proven more suitable for achieving high-precision,deep holes in metal materials.Nonetheless,excessive repetition rates can also result in severe thermal damage.Various methods are commonly employed for controlling taper,including parameter optimization,assistance,and secondary modification.Tilted laser beam drilling is widely utilized and has been integrated into relevant machining systems for commercial applications.Typical deep microholes include film cooling holes and injection microholes.Laser drilling is a potential machining method for new materials in the aerospace field.Although laser drilling processing has been studied,numerous related scientific challenges and technical difficulties must be addressed before practical im-plementation.
      原文链接:
    • 万方数据
    • 维普

    Spatial light modulation for femtosecond laser manufacturing:Current developments and challenges

    ZANG XueLIU ZiTingXU YiShiWANG Yi...
    60-72页
    查看更多>>摘要：Since the invention of lasers,spatial-light-modulated laser processing has become a powerful tool for various applications.It enables multidimensional and dynamic modulation of the laser beam,which significantly improves the processing efficiency,accuracy,and flexibility,and presents wider prospects over traditional mechanical technologies for machining three-dimen-sional,hard,brittle,or transparent materials.In this review,we introduce:(1)The role of spatial light modulation technology in the development of femtosecond laser manufacturing;(2)the structured light generated by spatial light modulation and its generation methods;and(3)representative applications of spatial-light-modulated femtosecond laser manufacturing,including aberration correction,parallel processing,focal field engineering,and polarization control.Finally,we summarize the present challenges in the field and possible future research.
      原文链接:
    • 万方数据
    • 维普

    In-situ analysis of laser-induced breakdown spectra for online monitoring of femtosecond laser machining of sapphire

    SHANGGUAN ShiYongZHANG JianGuoLI ZhanZhuSHI Wei...
    73-82页
    查看更多>>摘要：Laser-induced breakdown spectroscopy(LIBS)is widely used for elemental analysis.However,its application for monitoring and analyzing a laser machining process by examining the changes in spectral information warrants further investigation.In this study,we investigate the effect of laser parameters on the spectra,variations in the time-resolved plasma emission spectra,and the relationship between the morphology of craters and plasma plume evolution during the femtosecond(fs)laser ablation of sapphire.The Boltzmann plot method and Stark's broadening model are employed to estimate the temporal temperature and electron density of the plasma plume,revealing the process of plasma evolution.This study aims to demonstrate the feasibility of LIBS for online monitoring of laser processing through experimental data and theoretical explanations.
      原文链接:
    • 万方数据
    • 维普

    Hot-exciton effects on exciton diffusion and circular polarization dynamics in a single PbI2 nanoflake

    XU ChenYuWANG LeiCUI LinGAO BingRong...
    83-90页
    查看更多>>摘要：As one of the emerging two-dimensional lead halide materials,lead iodide(PbI2)nanosheets have proven to possess strong application potential in the fields of high-energy radiation detection and highly efficient perovskite solar cells.However,the underlying photophysical properties such as hot-exciton-related carrier dynamics remain unclear for PbI2 nanosheets.Here,we report the exciton dynamics of a single PbI2 nanoflake prepared by an aqueous solution method.Through a three-dimensional(3D)diffusion model,we obtain the exciton annihilation radius and diffusion coefficient of a single PbI2 nanoflake under non-resonant and resonant excitation conditions of band-edge exciton state.As initial exciton densities increase,we find the carrier recombination mechanism for a single PbI2 nanoflake gradually changes from exciton-exciton annihilation to free-carrier recombination.Finally,we reveal the room-temperature circular polarization of a single PbI2 nanoflake is due to free-carrier recombination with a band-edge exciton dissociation time of～120 fs under the resonant excitation condition.
      原文链接:
    • 万方数据

    Ultrafast investigation of room temperature valley polarization in"optical bilayer"WS2

    ZHAO LeYiWANG HaiLIU TianYuLI FangFei...
    91-97页
    查看更多>>摘要：Monolayer transition metal dichalcogenides(TMDCs)have become a promising platform in valleytronics due to possessing the regulatable valley degrees of freedom.While,as a result of the rapid intervalley scattering,it is difficult to measure the PL valley polarization of monolayer TMDCs at room temperature,which limits their application in valleytronics devices.Here,we report a room temperature photoluminescence(PL)valley polarization up to 3.73％in an"optical bilayer"WS2 formed by transferring monolayer WS2 onto flat Ag film.Furthermore,in the transient absorption(TA)measurements,a remarkably long valley depolarization lifetime is found.Thus,we demonstrate the valley properties of such"optical bilayer"WS2 resemble actual bilayer WS2,in which the robust valley polarization can be attributed to the phonons depletion effect and the blocked interlayer hopping processes.These peculiar valley features in"optical bilayer"WS2 provide a particularly simple method to enhance valley control at room temperature.
      原文链接:
    • 万方数据

    Realization of one-dimensional 2n-root topological states in photonic lattices

    WEI RuiShanZHANG QingLongYANG DanDanHUANG XiongJian...
    98-104页
    查看更多>>摘要：Square-root topological insulators recently discovered are intriguing topological phases.They possess topological properties inherited from the squared Hamiltonian and exhibit double-band structures.The mechanism of the square root was generalized to 2n-root topological insulators,giving rise to more band gaps.In this study,we describe the experimental realization of one-dimensional 2n-root topological insulators in photonic waveguide arrays using the archetypical Su-Schrieffer-Heeger(SSH)model.Topological edge states with tunable numbers are clearly observed under visible light.In particular,we visualized the dynamic evolutions of the light propagation by varying the sample lengths,which further proved the localization and multiple numbers of edge states in 2n-root topological systems.The experiment,which involves constructing 2n-root topological photonic lattices in various geometric arrangements,provides a stable platform for studying topological states that exhibit a remarkable degree of flexibility and control.
      原文链接:
    • 万方数据

    Causal reasoning in typical computer vision tasks

    ZHANG KeXuanSUN QiYuZHAO ChaoQiangTANG Yang...
    105-120页
    查看更多>>摘要：Deep learning has revolutionized the field of artificial intelligence.Based on the statistical correlations uncovered by deep learning-based methods,computer vision tasks,such as autonomous driving and robotics,are growing rapidly.Despite being the basis of deep learning,such correlation strongly depends on the distribution of the original data and is susceptible to un-controlled factors.Without the guidance of prior knowledge,statistical correlations alone cannot correctly reflect the essential causal relations and may even introduce spurious correlations.As a result,researchers are now trying to enhance deep leaming-based methods with causal theory.Causal theory can model the intrinsic causal structure unaffected by data bias and effectively avoids spurious correlations.This paper aims to comprehensively review the existing causal methods in typical vision and vision-language tasks such as semantic segmentation,object detection,and image captioning.The advantages of causality and the approaches for building causal paradigms will be summarized.Future roadmaps are also proposed,including facilitating the development of causal theory and its application in other complex scenarios and systems.
      原文链接:
    • 万方数据
    • 维普