Three coupling coefficients are defined to describe spatiotemporal coupling in ultrashort pulses. With these coupling coefficients, the first-order spatiotemporal couplings of Gaussian pulse and beam are described ana...Three coupling coefficients are defined to describe spatiotemporal coupling in ultrashort pulses. With these coupling coefficients, the first-order spatiotemporal couplings of Gaussian pulse and beam are described analytically. Also, the first-order and the second-order spatiotemporal couplings caused by angular dispersion elements are studied using these coupling coefficients. It can be shown that these coupling coefficients are dimensionless and normalized, and readily indicate the severity of spatiotemporal coupling.展开更多
Emerging multi-PW-class lasers and their envisioned laser-plasma interaction applications in unprecedented intensity regimes set a very demanding frame for the precise understanding of the finest properties of these s...Emerging multi-PW-class lasers and their envisioned laser-plasma interaction applications in unprecedented intensity regimes set a very demanding frame for the precise understanding of the finest properties of these systems.In this work we present a synthesis of simulation studies on a series of less known or even completely disregarded spatiotemporal effects that could potentially impact greatly the performances of high-intensity lasers.展开更多
Currently,numerical models based on idealized assumptions,complex algorithms and high computational costs are unsatisfactory for ocean surface current prediction.Moreover,the complex temporal and spatial variability o...Currently,numerical models based on idealized assumptions,complex algorithms and high computational costs are unsatisfactory for ocean surface current prediction.Moreover,the complex temporal and spatial variability of ocean currents also makes the prediction methods based on time series data challenging.The deep network model can automatically learn and extract complex features hidden in large amount of complex data,so it is a promising method for high quality prediction of ocean currents.In this paper,we propose a spatiotemporal coupled attention deep network model STCANet that can extract abundant temporal and spatial coupling information on the behavior characteristics of ocean currents for improving the prediction accuracy.Firstly,Spatial Module is designed and implemented to extract the spatiotemporal coupling characteristics of ocean currents,and meanwhile the spatial correlations and dependencies among adjacent sea areas are obtained through Spatial Channel Attention Module(SCAM).Secondly,we use the GatedRecurrent-Unit(GRU)to extract temporal relationships of ocean currents,and design and implement the nearest neighbor time attention module to extract the interdependences of ocean currents between adjacent times,which can further improve the accuracy of ocean current prediction.Finally,a series of comparative experiments on the MediSea_Dataset and EastSea_Dataset showed that the prediction quality of our model greatly outperforms those of other benchmark models such as History Average(HA),Autoregressive Integrated Moving Average Model(ARIMA),Long Short-term Memory(LSTM),Gate Recurrent Unit(GRU)and CNN_GRU.展开更多
Spatiotemporal optical vortices(STOVs)are distinguished by their intricate phase structures and orbital angular momentum properties.This study demonstrates a coherent 4Pi-focused method generating STOV arrays by tight...Spatiotemporal optical vortices(STOVs)are distinguished by their intricate phase structures and orbital angular momentum properties.This study demonstrates a coherent 4Pi-focused method generating STOV arrays by tightly focusing the wave packets carrying spatiotemporal vortices and an additional spatial vortex.Numerical simulations reveal that the structural characteristics of the STOV array are governed by the interplay between the spatiotemporal and spatial topological charges of the incident wave packet.Notably,the introduction of spin angular momentum into the wave packet induces spin-orbit coupling,resulting in a distinctive tilt of the STOV array.These findings open potential pathways for high-dimensional optical manipulation and advanced optical information multiplexing.展开更多
Temporal contrast is one of the crucial physical determinants which guarantee the successful performance of laser–matter interaction experiments. We generally reviewed the influences on the temporal contrast in three...Temporal contrast is one of the crucial physical determinants which guarantee the successful performance of laser–matter interaction experiments. We generally reviewed the influences on the temporal contrast in three categories of noises based on the requirement by the physical mechanisms. The spatiotemporal influences on temporal contrast at the focal region of the chromatic aberration and propagation time difference introduced by large-aperture broadband spatial filters, which were spatiotemporally coupled with compression and focusing, were calculated and discussed with a practical case in SG-Ⅱ5 PW ultrashort petawatt laser. The system-wide spatiotemporal coupling existing in large-aperture broadband ultrashort petawatt lasers was proved to be one of the possible causes of temporal contrast degradation in the focal region.展开更多
China’s urbanization has entered a mid-to-late phase,and is characterized by high-density urban engineering projects that form systems coupled to geotechnical environments.These systems exhibit significant vulnerabil...China’s urbanization has entered a mid-to-late phase,and is characterized by high-density urban engineering projects that form systems coupled to geotechnical environments.These systems exhibit significant vulnerability due to strong spatiotemporal coupling,which hampers sustainable urban development.Traditional approaches to urban engineering design,construction,and maintenance tend to focus on individual projects and lack the ability to comprehensively evaluate system-level sustainability.Thus,with current methods,it is difficult to optimize the renewal and operation of high-density urban engineering systems.In this study,the constituent elements and key features of high-density urban engineering systems are discussed,and urban engineering system sustainability evaluation indicators are comprehensively reviewed.Viewed from perspectives of resilience,low-carbon development,and ecological impact,66 performance indicators describing urban engineering systems are selected.The decision-making trial and evaluation laboratory(DEMATEL)-based analytic network process(DANP)method and the entropy weight method(EWM)are utilized to calculate these indicators’subjective and objective weights,respectively.Furthermore,the coupling relationships between evaluation indicators are explored,aiding the construction of an urban engineering sustainability evaluation index system.Finally,empirical analysis is conducted across six megacities in China(Tianjin,Hangzhou,Shanghai,Wuhan,Chongqing,and Shenzhen)to validate the effectiveness of the evaluation indicators.The findings reveal significant imbalances in the sustainability of urban engineering systems in China.Accordingly,potential strategies and indicators for targeted enhancement of these systems are discussed.展开更多
We explore an emerging frontier in optical communications-leveraging optical computing and optical signal processing to restore degraded signals in space or mode-division multiplexing(SDM/MDM)systems.As SDM/MDM pushes...We explore an emerging frontier in optical communications-leveraging optical computing and optical signal processing to restore degraded signals in space or mode-division multiplexing(SDM/MDM)systems.As SDM/MDM pushes toward ever-higher channel densities within a single fiber,inter-channel optical coupling leads to significant crosstalk.Due to group velocity mismatches,this crosstalk spatiotemporally entangles optical signal streams,significantly complicating multi-input multi-output digital signal processing(MIMO DSP)for signal recovery across both spatial and temporal domains.Free-space optical systems face similar challenges from multipath interference.We systematically appraise two strategic pathways of optically addressing the spatiotemporal interference:(1)optoelectronic computing that either accelerates conventional linear MIMO DSP or maps the problem onto physics-inspired models solvable by analog or hybrid optoelectronic systems and(2)all-optical processing that seeks to untangle the coupled optical signals directly within the optical domain.For both pathways,we evaluate architectural effectiveness and scalability based on rigorous mathematical analysis,aiming to offer insights into promising approaches for future research.展开更多
Diffraction,inherently linked to angular spectrum and affected by spatiotemporal coupling effects,imposes a fundamental limit on wave packets propagation.This limitation is particularly acute for spatiotemporal vortex...Diffraction,inherently linked to angular spectrum and affected by spatiotemporal coupling effects,imposes a fundamental limit on wave packets propagation.This limitation is particularly acute for spatiotemporal vortex beams,where diffraction distorts the beam profile and splits topological charges.While spatiotemporal coupling engineering has enabled diffraction-free(or propagation-invariant)wave packet propagation,achieving stable vortex propagation remains a significant challenge due to inherent constraints of regular wave dispersion.Here,we overcome this challenge by tailoring the wave system’s dispersion to achieve both propagation-invariant behavior and stable vortex structures.We present the first experimental demonstration of propagation-invariant spatiotemporal vortex beams that maintain their spatiotemporal profiles and topological charges over extended propagation distances.The ability of these wave packets to stably carry diverse topological charges without splitting or deformation provides critical insights into spatiotemporal vortex dynamics and unlocks new possibilities for applications across optics,acoustics,and beyond.展开更多
基金supported by the Program for New Century Excellent Talents in University(NCET),China(Grant No.NCET-05-0784)
文摘Three coupling coefficients are defined to describe spatiotemporal coupling in ultrashort pulses. With these coupling coefficients, the first-order spatiotemporal couplings of Gaussian pulse and beam are described analytically. Also, the first-order and the second-order spatiotemporal couplings caused by angular dispersion elements are studied using these coupling coefficients. It can be shown that these coupling coefficients are dimensionless and normalized, and readily indicate the severity of spatiotemporal coupling.
文摘Emerging multi-PW-class lasers and their envisioned laser-plasma interaction applications in unprecedented intensity regimes set a very demanding frame for the precise understanding of the finest properties of these systems.In this work we present a synthesis of simulation studies on a series of less known or even completely disregarded spatiotemporal effects that could potentially impact greatly the performances of high-intensity lasers.
基金The authors would like to thank the financial support from the National Key Research and Development Program of China(Nos.2020YFE0201200,2019YFC1509100)the partial support by the Youth Program of Natural Science Foundation of China(No.41706010)the Fundamental Research Funds for the Central Universities(No.202264002).
文摘Currently,numerical models based on idealized assumptions,complex algorithms and high computational costs are unsatisfactory for ocean surface current prediction.Moreover,the complex temporal and spatial variability of ocean currents also makes the prediction methods based on time series data challenging.The deep network model can automatically learn and extract complex features hidden in large amount of complex data,so it is a promising method for high quality prediction of ocean currents.In this paper,we propose a spatiotemporal coupled attention deep network model STCANet that can extract abundant temporal and spatial coupling information on the behavior characteristics of ocean currents for improving the prediction accuracy.Firstly,Spatial Module is designed and implemented to extract the spatiotemporal coupling characteristics of ocean currents,and meanwhile the spatial correlations and dependencies among adjacent sea areas are obtained through Spatial Channel Attention Module(SCAM).Secondly,we use the GatedRecurrent-Unit(GRU)to extract temporal relationships of ocean currents,and design and implement the nearest neighbor time attention module to extract the interdependences of ocean currents between adjacent times,which can further improve the accuracy of ocean current prediction.Finally,a series of comparative experiments on the MediSea_Dataset and EastSea_Dataset showed that the prediction quality of our model greatly outperforms those of other benchmark models such as History Average(HA),Autoregressive Integrated Moving Average Model(ARIMA),Long Short-term Memory(LSTM),Gate Recurrent Unit(GRU)and CNN_GRU.
基金supported by the National Natural Science Foundation of China(Nos.12274074 and 12134013)the Natural Science Foundation of Jiangsu Province(No.BK20242024)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX25_0437)。
文摘Spatiotemporal optical vortices(STOVs)are distinguished by their intricate phase structures and orbital angular momentum properties.This study demonstrates a coherent 4Pi-focused method generating STOV arrays by tightly focusing the wave packets carrying spatiotemporal vortices and an additional spatial vortex.Numerical simulations reveal that the structural characteristics of the STOV array are governed by the interplay between the spatiotemporal and spatial topological charges of the incident wave packet.Notably,the introduction of spin angular momentum into the wave packet induces spin-orbit coupling,resulting in a distinctive tilt of the STOV array.These findings open potential pathways for high-dimensional optical manipulation and advanced optical information multiplexing.
基金supported by the National Natural Science Foundation of China (NSFC) (No. 11304332)Key Projects of International Cooperation in Chinese Academy of Sciences
文摘Temporal contrast is one of the crucial physical determinants which guarantee the successful performance of laser–matter interaction experiments. We generally reviewed the influences on the temporal contrast in three categories of noises based on the requirement by the physical mechanisms. The spatiotemporal influences on temporal contrast at the focal region of the chromatic aberration and propagation time difference introduced by large-aperture broadband spatial filters, which were spatiotemporally coupled with compression and focusing, were calculated and discussed with a practical case in SG-Ⅱ5 PW ultrashort petawatt laser. The system-wide spatiotemporal coupling existing in large-aperture broadband ultrashort petawatt lasers was proved to be one of the possible causes of temporal contrast degradation in the focal region.
基金supported by the Fundamental Research Funds for the Central Universities(No.226-2024-00242)the Excellent Research Groups Project(No.52588202)the National Science Fund for Distinguished Young Scholars of China(No.52125803).
文摘China’s urbanization has entered a mid-to-late phase,and is characterized by high-density urban engineering projects that form systems coupled to geotechnical environments.These systems exhibit significant vulnerability due to strong spatiotemporal coupling,which hampers sustainable urban development.Traditional approaches to urban engineering design,construction,and maintenance tend to focus on individual projects and lack the ability to comprehensively evaluate system-level sustainability.Thus,with current methods,it is difficult to optimize the renewal and operation of high-density urban engineering systems.In this study,the constituent elements and key features of high-density urban engineering systems are discussed,and urban engineering system sustainability evaluation indicators are comprehensively reviewed.Viewed from perspectives of resilience,low-carbon development,and ecological impact,66 performance indicators describing urban engineering systems are selected.The decision-making trial and evaluation laboratory(DEMATEL)-based analytic network process(DANP)method and the entropy weight method(EWM)are utilized to calculate these indicators’subjective and objective weights,respectively.Furthermore,the coupling relationships between evaluation indicators are explored,aiding the construction of an urban engineering sustainability evaluation index system.Finally,empirical analysis is conducted across six megacities in China(Tianjin,Hangzhou,Shanghai,Wuhan,Chongqing,and Shenzhen)to validate the effectiveness of the evaluation indicators.The findings reveal significant imbalances in the sustainability of urban engineering systems in China.Accordingly,potential strategies and indicators for targeted enhancement of these systems are discussed.
基金supported by the National Natural Science Foundation of China(NSFC)(Projects 62335019 and 62475294)the Innovation Program for Quantum Science and Technology(Project 2021ZD0301401)the National Key Research and Development Program of China(Grant 2024YFB2908100).
文摘We explore an emerging frontier in optical communications-leveraging optical computing and optical signal processing to restore degraded signals in space or mode-division multiplexing(SDM/MDM)systems.As SDM/MDM pushes toward ever-higher channel densities within a single fiber,inter-channel optical coupling leads to significant crosstalk.Due to group velocity mismatches,this crosstalk spatiotemporally entangles optical signal streams,significantly complicating multi-input multi-output digital signal processing(MIMO DSP)for signal recovery across both spatial and temporal domains.Free-space optical systems face similar challenges from multipath interference.We systematically appraise two strategic pathways of optically addressing the spatiotemporal interference:(1)optoelectronic computing that either accelerates conventional linear MIMO DSP or maps the problem onto physics-inspired models solvable by analog or hybrid optoelectronic systems and(2)all-optical processing that seeks to untangle the coupled optical signals directly within the optical domain.For both pathways,we evaluate architectural effectiveness and scalability based on rigorous mathematical analysis,aiming to offer insights into promising approaches for future research.
基金supported by the National Key Research and Development Program of China(2023YFA1406900 and 2022YFA1404800)the National Natural Science Foundation of China(12234007,12321161645,12221004,T2394480,and T2394481)+1 种基金Science and Technology Commission of Shanghai Municipality(22142200400,21DZ1101500,2019SHZDZX01,and 23DZ2260100)China Postdoctoral Science Foundation(2022M720810 and 2022TQ0078).
文摘Diffraction,inherently linked to angular spectrum and affected by spatiotemporal coupling effects,imposes a fundamental limit on wave packets propagation.This limitation is particularly acute for spatiotemporal vortex beams,where diffraction distorts the beam profile and splits topological charges.While spatiotemporal coupling engineering has enabled diffraction-free(or propagation-invariant)wave packet propagation,achieving stable vortex propagation remains a significant challenge due to inherent constraints of regular wave dispersion.Here,we overcome this challenge by tailoring the wave system’s dispersion to achieve both propagation-invariant behavior and stable vortex structures.We present the first experimental demonstration of propagation-invariant spatiotemporal vortex beams that maintain their spatiotemporal profiles and topological charges over extended propagation distances.The ability of these wave packets to stably carry diverse topological charges without splitting or deformation provides critical insights into spatiotemporal vortex dynamics and unlocks new possibilities for applications across optics,acoustics,and beyond.
