The ultrafast laser-matter interaction is explored to induce new pioneering principles and technologies into the realms of fundamental science and industrial production.The local thermal melting and connection propert...The ultrafast laser-matter interaction is explored to induce new pioneering principles and technologies into the realms of fundamental science and industrial production.The local thermal melting and connection properties of the ultrafast laser welding technology offer a novel method for welding of diverse transparent materials,thus having wide range of potential applications in aerospace,opto-mechanical systems,sensors,microfluidic,optics,etc.In this comprehensive review,tuning the transient electron activation processes,high-rate laser energy deposition,and dynamic evolution of plasma morphology by the temporal/spatial shaping methods have been demonstrated to facilitate the transition from conventional homogeneous transparent material welding to the more intricate realm of transparent/metal heterogeneous material welding.The welding strength and stability are also improvable through the implementation of real-time,in-situ monitoring techniques and the prompt diagnosis of welding defects.The principles of ultrafast laser welding,bottleneck problems in the welding,novel welding methods,advances in welding performance,in-situ monitoring and diagnosis,and various applications are reviewed.Finally,we offer a forward-looking perspective on the fundamental challenges within the field of ultrafast laser welding and identify key areas for future research,underscoring the imperative need for ongoing innovation and exploration.展开更多
This review examines the state-of-the-art in spatial manipulation of ultrafast laser processing using dynamic light modulators,with a particular focus on liquid crystal-based systems.We discuss phase modulation strate...This review examines the state-of-the-art in spatial manipulation of ultrafast laser processing using dynamic light modulators,with a particular focus on liquid crystal-based systems.We discuss phase modulation strategies and highlight the current limitations and challenges in surface and bulk processing.Specifically,we emphasize the delicate balance between high-fidelity beam shaping and energy efficiency,both critical for surface and bulk processing applications.Given the inherent physical limitations of spatial light modulators such as spatial resolution,fill factor,and phase modulation range.We explore techniques developed to bridge the gap between desired intensity distributions and actual experimental beam profiles.We present various laser light modulation technologies and the main algorithmic strategies for obtaining modulation patterns.The paper includes application examples across a wide range of fields,from surgery to surface structuring,cutting,bulk photo-inscription of optical functions,and additive manufacturing,highlighting the significant enhancements in processing speed and precision due to spatial beam shaping.The diverse applications and the technological limitations underscore the need for adapted modulation pattern calculation methods.We discuss several advancements addressing these challenges,involving both experimental and algorithmic developments,including the recent incorporation of artificial intelligence.Additionally,we cover recent progress in phase and pulse front control based on spatial modulators,which introduces an extra control parameter for light excitation with high potential for achieving more controlled processing outcomes.展开更多
This article elaborated the characteristics of settlement shape in detail with examples. Aiming at the negative effects on settlement shape by construction, we put forward some measures, such as respect for ecological...This article elaborated the characteristics of settlement shape in detail with examples. Aiming at the negative effects on settlement shape by construction, we put forward some measures, such as respect for ecological environment, selection mode of space development, protection of historical features, and excavation of culture connotation, so as to realize the protection of settlement shape.展开更多
.Nanochannel structures with a feature size deeply under the diffraction limit and a high aspect ratio hold huge biomedical significance,which is especially challenging to be realized on hard and brittle materials,suc....Nanochannel structures with a feature size deeply under the diffraction limit and a high aspect ratio hold huge biomedical significance,which is especially challenging to be realized on hard and brittle materials,such as silica,diamond,and sapphire.By simultaneously depositing the pulse energy on the surface and inside the sample,nanochannels with the smallest feature size of 18 nm(∼1∕30λ)and more than 200 aspect ratios are achieved inside silica,the mechanism of which can be concluded as the surface assisting material ejection effect.Both the experimental and theoretical results prove that the coaction of the superficial“hot domain”and internal hot domain dominates the generation of the nanochannels,which gives new insights into the laser-material interacting mechanisms and potentially promotes the corresponding application fields.展开更多
Based on the optical activity of quartz crystal, we proposed a scheme for shaping the spatial intensity distribution of a linearly polarized laser beam by utilizing a quartz crystal piano-convex lens in combination wi...Based on the optical activity of quartz crystal, we proposed a scheme for shaping the spatial intensity distribution of a linearly polarized laser beam by utilizing a quartz crystal piano-convex lens in combination with a polarizer. The intensity profile of the shaped laser beam can be easily switched from one profile to another by controlling the polarization direction of the incident laser beam.展开更多
The electrochemical conversion of CO_(2) into value-added chemicals presents an environmentally sustainable alternative to conventional fossil-derived processes,yet achieving high selectivity remains challenging due t...The electrochemical conversion of CO_(2) into value-added chemicals presents an environmentally sustainable alternative to conventional fossil-derived processes,yet achieving high selectivity remains challenging due to competing reaction pathways.Here,we demonstrate precise tuning of CO_(2) electroreduction pathways through femtosecond laser-driven surface doping of Cu with targeted metals,achieving Faradaic efficiencies of 58.9%for CO,67.9%for formate,and 37.8%for ethylene.This spatially shaping laser technique enables nanoscale deposition of any metal(including Sb,Sn,Re,La,In,Co,Ni,Ag,and Pt)onto Cu foil,forming compositionally graded Cu-based bimetallic surfaces with controlled atomic ratios.Systematic electronic structure analysis reveals that secondary metals induce d-band center shifts spanning−0.21 to+0.78 eV,governing intermediate adsorption energetics-upward shifts strengthen*CO binding via enhanced back-donation,while downward shifts generally weaken adsorbate interactions.Through precise control of Cu/Sn and Cu/Sb atomic ratios,we manipulate electronic structures of CuSn and CuSb catalysts and consequently demonstrate continuous tuning of formate(19.0%-67.9%)and CO(18.8%-58.9%)selectivity.In-situ Raman spectroscopy and valence band X-ray photoelectron spectroscopy(XPS)elucidate dual modulation mechanisms.Sn enhances CO desorption by weakening*CO adsorption,whereas La promotes ethylene formation through optimized CO absorption and dimerization.The tunability of the reaction pathways aligns with metal-dependent stabilization of critical intermediates(CO and*OCHO).This work introduces a nanoscale-depth and trace-level multi-elemental loading strategy with tunable ratios on copper electrodes,enabling precise electronic structure manipulation of Cu-based electrocatalysts to mechanistically elucidate the correlation between surface electronic states and product selectivity,offering a roadmap to design and modulate Cu-based catalysts for selective CO_(2)-to-chemical conversion and beyond via low-cost laser processing techniques.展开更多
This paper presents a comprehensive technical overview of the Linac Coherent Light Source II(LCLS-II)photoinjector laser system,its first and foremost component.The LCLS-II photoinjector laser system serves as an upgr...This paper presents a comprehensive technical overview of the Linac Coherent Light Source II(LCLS-II)photoinjector laser system,its first and foremost component.The LCLS-II photoinjector laser system serves as an upgrade to the original LCLS at SLAC National Accelerator Laboratory.This advanced laser system generates high-quality laser beams for the LCLS-II,contributing to the instrument's unprecedented brightness,precision and flexibility.Our discussion extends to the various subsystems that comprise the photoinjector,including the photocathode laser,laser heater and beam transport systems.Lastly,we draw attention to the ongoing research and development infrastructure underway to enhance the functionality and efficiency of the LCLS-II,and similar X-ray free-electron laser facilities around the world,thereby contributing to the future of laser technology and its applications.展开更多
This paper constructs a general equilibrium spatial urban model and measures city geometric compactness using the patch-shape index based on evidence from satellite imagery and basic vector maps of China.It adopts the...This paper constructs a general equilibrium spatial urban model and measures city geometric compactness using the patch-shape index based on evidence from satellite imagery and basic vector maps of China.It adopts the ordinary least squares and instrumental variable approaches to examine the effect of city shape on the urban development of 279 Chinese cities at or above the prefecture level.The empirical results show that there was a significant negative correlation between city shape and economic outcomes.Specifically,every 1 percentage point increase in the patch-shape index led to a decrease in city-scale GDP by 0.009 percent,housing prices by 0.044 percent,and wages by 0.024 percent.More compact urban layouts attracted an inflow of households and firms,stimulated city economic growth,and were associated with increased housing prices and wage rates.The paper considers the cities'initial conditions,trends in population changes(expanding,shrinking,and stagnant cities),and geographic factors,and finds that the results are robust.An array of policy implications can be drawn from the research.展开更多
A high power laser system was used to drive the ignition of inertial confinement fusion(ICF), of which the high energy,the uniform focal spot, the accurate laser waveform, and the synchronization between the laser bea...A high power laser system was used to drive the ignition of inertial confinement fusion(ICF), of which the high energy,the uniform focal spot, the accurate laser waveform, and the synchronization between the laser beams are key parameters.To accomplish this, global laser characteristics control should be assured, which was the main purpose of the injection laser system. In this paper, the key technological progress involved in the improvement of the performance of the injection laser of SG-II is reported, including frequency domain control, time domain control, near-field spatial shaping, preamplifier technology, and the optical parametric chirped pulse amplification pump source.展开更多
基金supports from National Key R&D Program of China(Grant No.2023YFB4605500)National Natural Science Foundation of China(Grant No.52105498)+3 种基金Natural Science Foundation of Hunan Province(Grant No.2022JJ40597)the Science and Technology Innovation Program of Hunan Province(Grant No.2022RC1132)State Key Laboratory of Precision Manufacturing for Extreme Service Performance(Grant No.ZZYJKT2023-08)support in analyzing the status of ultrafast laser welding applications,as well as the corresponding project support(Grant No.HKF202400595).
文摘The ultrafast laser-matter interaction is explored to induce new pioneering principles and technologies into the realms of fundamental science and industrial production.The local thermal melting and connection properties of the ultrafast laser welding technology offer a novel method for welding of diverse transparent materials,thus having wide range of potential applications in aerospace,opto-mechanical systems,sensors,microfluidic,optics,etc.In this comprehensive review,tuning the transient electron activation processes,high-rate laser energy deposition,and dynamic evolution of plasma morphology by the temporal/spatial shaping methods have been demonstrated to facilitate the transition from conventional homogeneous transparent material welding to the more intricate realm of transparent/metal heterogeneous material welding.The welding strength and stability are also improvable through the implementation of real-time,in-situ monitoring techniques and the prompt diagnosis of welding defects.The principles of ultrafast laser welding,bottleneck problems in the welding,novel welding methods,advances in welding performance,in-situ monitoring and diagnosis,and various applications are reviewed.Finally,we offer a forward-looking perspective on the fundamental challenges within the field of ultrafast laser welding and identify key areas for future research,underscoring the imperative need for ongoing innovation and exploration.
基金supported by the French ANRT agence nationale de la recherche technologique under the CIFRE conventions industrielles de formation par la recherche framework.
文摘This review examines the state-of-the-art in spatial manipulation of ultrafast laser processing using dynamic light modulators,with a particular focus on liquid crystal-based systems.We discuss phase modulation strategies and highlight the current limitations and challenges in surface and bulk processing.Specifically,we emphasize the delicate balance between high-fidelity beam shaping and energy efficiency,both critical for surface and bulk processing applications.Given the inherent physical limitations of spatial light modulators such as spatial resolution,fill factor,and phase modulation range.We explore techniques developed to bridge the gap between desired intensity distributions and actual experimental beam profiles.We present various laser light modulation technologies and the main algorithmic strategies for obtaining modulation patterns.The paper includes application examples across a wide range of fields,from surgery to surface structuring,cutting,bulk photo-inscription of optical functions,and additive manufacturing,highlighting the significant enhancements in processing speed and precision due to spatial beam shaping.The diverse applications and the technological limitations underscore the need for adapted modulation pattern calculation methods.We discuss several advancements addressing these challenges,involving both experimental and algorithmic developments,including the recent incorporation of artificial intelligence.Additionally,we cover recent progress in phase and pulse front control based on spatial modulators,which introduces an extra control parameter for light excitation with high potential for achieving more controlled processing outcomes.
基金Supported by the 11th 5-year Scientific Supporting Project Fund of the Ministry of Science and Technology(2006BAJ01A12-06)the 11th 5-years Planning Philosophy and Social Science Project of Sichuan Province(SC06B014)~~
文摘This article elaborated the characteristics of settlement shape in detail with examples. Aiming at the negative effects on settlement shape by construction, we put forward some measures, such as respect for ecological environment, selection mode of space development, protection of historical features, and excavation of culture connotation, so as to realize the protection of settlement shape.
基金supported by the National Natural Science Foundation of China under Grant Nos.12127806,62175195,and 61875158the International Joint Research Laboratory for Micro/Nano Manufacturing and Measurement Technologies,and the Fundamental Research Funds for the Central Universities.
文摘.Nanochannel structures with a feature size deeply under the diffraction limit and a high aspect ratio hold huge biomedical significance,which is especially challenging to be realized on hard and brittle materials,such as silica,diamond,and sapphire.By simultaneously depositing the pulse energy on the surface and inside the sample,nanochannels with the smallest feature size of 18 nm(∼1∕30λ)and more than 200 aspect ratios are achieved inside silica,the mechanism of which can be concluded as the surface assisting material ejection effect.Both the experimental and theoretical results prove that the coaction of the superficial“hot domain”and internal hot domain dominates the generation of the nanochannels,which gives new insights into the laser-material interacting mechanisms and potentially promotes the corresponding application fields.
基金the National"863"Project in Advanced Techniques in China under Grant No.2007AA804801.
文摘Based on the optical activity of quartz crystal, we proposed a scheme for shaping the spatial intensity distribution of a linearly polarized laser beam by utilizing a quartz crystal piano-convex lens in combination with a polarizer. The intensity profile of the shaped laser beam can be easily switched from one profile to another by controlling the polarization direction of the incident laser beam.
基金supported by the National Key R&D Program of China(No.2022YFB4601300)Aeronautical Science Fund(No.3030021252404)+2 种基金the National Natural Science Foundation of China(NSFC,No.52475425)the NSFC Basic Sciences Center Program(Extreme Light Field Manufacturing,No.52488301)We thank the Analytical&Testing Center of Beijing Institute of Technology for providing XPS and valence band measurements.We thank the BL02B01 and BL01B Beamlines at Shanghai Synchrotron Radiation Facility(SSRF),supported by the NSFC(No.11227902),for photoelectron spectroscopy and vibrational spectroscopy studies.We thank the support from beamline BL11U and BL10B at the National Synchrotron Radiation Laboratory(NSRL)in Hefei,China,for the synchrotron radiation and X-ray spectroscopic measurements.
文摘The electrochemical conversion of CO_(2) into value-added chemicals presents an environmentally sustainable alternative to conventional fossil-derived processes,yet achieving high selectivity remains challenging due to competing reaction pathways.Here,we demonstrate precise tuning of CO_(2) electroreduction pathways through femtosecond laser-driven surface doping of Cu with targeted metals,achieving Faradaic efficiencies of 58.9%for CO,67.9%for formate,and 37.8%for ethylene.This spatially shaping laser technique enables nanoscale deposition of any metal(including Sb,Sn,Re,La,In,Co,Ni,Ag,and Pt)onto Cu foil,forming compositionally graded Cu-based bimetallic surfaces with controlled atomic ratios.Systematic electronic structure analysis reveals that secondary metals induce d-band center shifts spanning−0.21 to+0.78 eV,governing intermediate adsorption energetics-upward shifts strengthen*CO binding via enhanced back-donation,while downward shifts generally weaken adsorbate interactions.Through precise control of Cu/Sn and Cu/Sb atomic ratios,we manipulate electronic structures of CuSn and CuSb catalysts and consequently demonstrate continuous tuning of formate(19.0%-67.9%)and CO(18.8%-58.9%)selectivity.In-situ Raman spectroscopy and valence band X-ray photoelectron spectroscopy(XPS)elucidate dual modulation mechanisms.Sn enhances CO desorption by weakening*CO adsorption,whereas La promotes ethylene formation through optimized CO absorption and dimerization.The tunability of the reaction pathways aligns with metal-dependent stabilization of critical intermediates(CO and*OCHO).This work introduces a nanoscale-depth and trace-level multi-elemental loading strategy with tunable ratios on copper electrodes,enabling precise electronic structure manipulation of Cu-based electrocatalysts to mechanistically elucidate the correlation between surface electronic states and product selectivity,offering a roadmap to design and modulate Cu-based catalysts for selective CO_(2)-to-chemical conversion and beyond via low-cost laser processing techniques.
基金the support from the SLAC National Accelerator Laboratory,the U.S.Department of Energy(DOE),the Office of Science,Office of Basic Energy Sciences under Contract No.DE-AC02-76SF00515,No.DE-SC0022559,No.DE-SC0022464,No.DE-FOA0002859the National Science Foundation under Contract No.2231334the U.S.Department of Defense under a National Defense Science and Engineering Fellowship。
文摘This paper presents a comprehensive technical overview of the Linac Coherent Light Source II(LCLS-II)photoinjector laser system,its first and foremost component.The LCLS-II photoinjector laser system serves as an upgrade to the original LCLS at SLAC National Accelerator Laboratory.This advanced laser system generates high-quality laser beams for the LCLS-II,contributing to the instrument's unprecedented brightness,precision and flexibility.Our discussion extends to the various subsystems that comprise the photoinjector,including the photocathode laser,laser heater and beam transport systems.Lastly,we draw attention to the ongoing research and development infrastructure underway to enhance the functionality and efficiency of the LCLS-II,and similar X-ray free-electron laser facilities around the world,thereby contributing to the future of laser technology and its applications.
基金the key project of the National Social Science Foundation(No.20&ZD168)the National Natural Science Foundation of China(No.71973102)for research grants.
文摘This paper constructs a general equilibrium spatial urban model and measures city geometric compactness using the patch-shape index based on evidence from satellite imagery and basic vector maps of China.It adopts the ordinary least squares and instrumental variable approaches to examine the effect of city shape on the urban development of 279 Chinese cities at or above the prefecture level.The empirical results show that there was a significant negative correlation between city shape and economic outcomes.Specifically,every 1 percentage point increase in the patch-shape index led to a decrease in city-scale GDP by 0.009 percent,housing prices by 0.044 percent,and wages by 0.024 percent.More compact urban layouts attracted an inflow of households and firms,stimulated city economic growth,and were associated with increased housing prices and wage rates.The paper considers the cities'initial conditions,trends in population changes(expanding,shrinking,and stagnant cities),and geographic factors,and finds that the results are robust.An array of policy implications can be drawn from the research.
文摘A high power laser system was used to drive the ignition of inertial confinement fusion(ICF), of which the high energy,the uniform focal spot, the accurate laser waveform, and the synchronization between the laser beams are key parameters.To accomplish this, global laser characteristics control should be assured, which was the main purpose of the injection laser system. In this paper, the key technological progress involved in the improvement of the performance of the injection laser of SG-II is reported, including frequency domain control, time domain control, near-field spatial shaping, preamplifier technology, and the optical parametric chirped pulse amplification pump source.
