Femtosecond laser technology has attracted significant attention from the viewpoints of fundamental and application;especially femtosecond laser processing materials present the unique mechanism of laser-material inte...Femtosecond laser technology has attracted significant attention from the viewpoints of fundamental and application;especially femtosecond laser processing materials present the unique mechanism of laser-material interaction.Under the extreme nonequilibrium conditions imposed by femtosecond laser irradiation,many fundamental questions concerning the physical origin of the material removal process remain unanswered.In this review,cutting-edge ultrafast dynamic observation techniques for investigating the fundamental questions,including timeresolved pump-probe shadowgraphy,ultrafast continuous optical imaging,and four-dimensional ultrafast scanning electron microscopy,are comprehensively surveyed.Each technique is described in depth,beginning with its basic principle,followed by a description of its representative applications in laser-material interaction and its strengths and limitations.The consideration of temporal and spatial resolutions and panoramic measurement at different scales are two major challenges.Hence,the prospects for technical advancement in this field are discussed finally.展开更多
Ag nanoparticles embedded in soda-lime silicate glass were fabricated by ion-exchange and subse-quently annealing method. Z-scan technique, femtosecond time-resolved optical Kerr effect (OKE) technique and femtosecond...Ag nanoparticles embedded in soda-lime silicate glass were fabricated by ion-exchange and subse-quently annealing method. Z-scan technique, femtosecond time-resolved optical Kerr effect (OKE) technique and femtosecond pump-probe experiment were used to investigate the effects of laser wavelength and laser pulse duration as well as annealing temperature on the third-order optical nonlinearity and ultrafast dynamics of the composites. It was found that the third-order susceptibility of Ag nanoparticles composite glass measured by 400 nm pulse source is larger than that measured by 800 nm pulse source due to an enhancement effect of local field near surface plasmon resonance of Ag nanoparticles in silicate glass. The third-order optical nonlinearity measured by ns laser source is about two orders of magnitude larger than that measured from fs pulse. The annealing temperature has an important effect on the third-order optical nonlinearity and ultrafast dynamics of the composites. Third-order nonlinear susceptibility up to 10?10 esu and fast relaxation process up to 0.2 ps have been obtained in Ag nanoparticles doped glass.展开更多
By numerically solving the time-dependent Schr?dinger equation and employing the analytical perturbative model,we investigated the chirp-induced electron vortex in the photoionization of hydrogen atoms by a pair of co...By numerically solving the time-dependent Schr?dinger equation and employing the analytical perturbative model,we investigated the chirp-induced electron vortex in the photoionization of hydrogen atoms by a pair of counter-rotating circularly polarized chirped attosecond extremely ultraviolet pulses.We demonstrated that single-photon ionization of hydrogen atoms generates photoelectron momentum distributions(PMDs)with distinct helical vortex structures either with or without a time delay between two counter-rotating circularly polarized laser pulses.These structures are highly sensitive to both the time delay between the pulses and their chirp parameters.Our analytical model reveals that the splitting of vortex spirals is caused by the sign changing of the chirp-induced frequency-dependent time delay.We showed that to obtain the counterpart of the PMD under a pair of counter-rotating circularly polarized chirped pulses,both chirp parameters and ordering of pulses need to be reversed.展开更多
About 30%of the world's primary energy consumption is in friction.The economic losses caused by friction energy dissipation and wear account for about 2%-7%of its gross domestic product(GDP)for different countries...About 30%of the world's primary energy consumption is in friction.The economic losses caused by friction energy dissipation and wear account for about 2%-7%of its gross domestic product(GDP)for different countries every year.The key to reducing energy consumption is to control the way of energy dissipation in the friction process.However,due to many various factors affecting friction and the lack of efficient detection methods,the energy dissipation mechanism in friction is still a challenging problem.Here,we firstly introduce the classical microscopic mechanism of friction energy dissipation,including phonon dissipation,electron dissipation,and non-contact friction energy dissipation.Then,we attempt to summarize the ultrafast friction energy dissipation and introduce the high-resolution friction energy dissipation detection system,since the origin of friction energy dissipation is essentially related to the ultrafast dynamics of excited electrons and phonons.Finally,the application of friction energy dissipation in representative high-end equipment is discussed,and the potential economic saving is predicted.展开更多
With the integration of ultrafast reflectivity and polarimetry probes,we observed carrier relaxation and spin dynamics induced by ultrafast laser excitation of Ni(111)single crystals.The carrier relaxation time within...With the integration of ultrafast reflectivity and polarimetry probes,we observed carrier relaxation and spin dynamics induced by ultrafast laser excitation of Ni(111)single crystals.The carrier relaxation time within the linear excitation range reveals that electron-phonon coupling and dissipation of photon energy into the bulk of the crystal take tens of picoseconds.On the other hand,the observed spin dynamics indicate a longer time of about 120 ps.To further understand how the lattice degree of freedom is coupled with these dynamics may require the integration of an ultrafast diffraction probe.展开更多
Chalcogenide superlattices Sb_(2)Te_(3)-GeTe is a candidate for interfacial phase-change memory(iPCM) data storage devices.By employing terahertz emission spectroscopy and the transient reflectance spectroscopy togeth...Chalcogenide superlattices Sb_(2)Te_(3)-GeTe is a candidate for interfacial phase-change memory(iPCM) data storage devices.By 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 superlattices.Sample 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 superlattices.By 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 coupling.These demonstrates play an important role in the development of iPCM-based high-speed optoelectronic devices.展开更多
Plasmonics has aroused tremendous interest in photophysics,nanophotonics,and metamaterials.The extreme field concentration of plasmonics offers the ultimate spatial and temporal light control,single-particle detection...Plasmonics has aroused tremendous interest in photophysics,nanophotonics,and metamaterials.The extreme field concentration of plasmonics offers the ultimate spatial and temporal light control,single-particle detection,and optical modulation.Plasmon decay of metal nanostructures into hot carriers extends the application into photocatalysis,photodetectors,photovoltaics,and ultrafast nanooptics.The generated hot electron–hole pairs are transferred into adjacent dielectrics,well known to be more efficient than the hot carrier generation in dielectrics by direct photoexcitations.However,plasmon-induced hot-carrier-based devices are far from practical applications due to the low quantum yield of hot carrier extraction.Emergent challenges include low hot carrier generation efficiency in metals,rapid energy loss of hot carriers,and severe charge recombination at the metal/dielectric interface.In this review,we provide a fundamental insight into the hot carrier generation,transport,injection,and diffusion into dielectrics based on the steady-state and time-resolved spectroscopic studies as well as theoretical calculations.Strategies to enhance hot carrier generation in metals and electron transfer into dielectrics are discussed in detail.Then,applications based on hot carrier transfer are introduced briefly.Finally,we provide our suggestions on future research endeavors.We believe this review will provide a valuable overall physical picture of plasmon-induced hot carrier applications for researchers.展开更多
Interlayer twist evokes revolutionary changes to the optical and electronic properties of twisted bilayer graphene(TBG)for electronics,photonics and optoelectronics.Although the ground state responses in TBG have been...Interlayer twist evokes revolutionary changes to the optical and electronic properties of twisted bilayer graphene(TBG)for electronics,photonics and optoelectronics.Although the ground state responses in TBG have been vastly and clearly studied,the dynamic process of its photoexcited carrier states mainly remains elusive.Here,we unveil the photoexcited hot carrier dynamics in TBG by time-resolved ultrafast photoluminescence(PL)autocorrelation spectroscopy.We demonstrate the unconventional ultrafast PL emission between the van Hove singularities(VHSs)with a~4 times prolonged relaxation lifetime.This intriguing photoexcited carrier behavior is ascribed to the abnormal hot carrier thermalization brought by bottleneck effects at VHSs and interlayer charge distribution process.Our study on hot carrier dynamics in TBG offers new insights into the excited states and correlated physics of graphene twistronics systems.展开更多
基金supported by the National Natural Science Foundation of China under Grant Nos.51975054,61605140 and 11704028the National Key R&D Program of China(2017YFB1104300)。
文摘Femtosecond laser technology has attracted significant attention from the viewpoints of fundamental and application;especially femtosecond laser processing materials present the unique mechanism of laser-material interaction.Under the extreme nonequilibrium conditions imposed by femtosecond laser irradiation,many fundamental questions concerning the physical origin of the material removal process remain unanswered.In this review,cutting-edge ultrafast dynamic observation techniques for investigating the fundamental questions,including timeresolved pump-probe shadowgraphy,ultrafast continuous optical imaging,and four-dimensional ultrafast scanning electron microscopy,are comprehensively surveyed.Each technique is described in depth,beginning with its basic principle,followed by a description of its representative applications in laser-material interaction and its strengths and limitations.The consideration of temporal and spatial resolutions and panoramic measurement at different scales are two major challenges.Hence,the prospects for technical advancement in this field are discussed finally.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 50672069, 10674031)the Key Item for Basic Research of Shanghai, China (Grant No. 05JC14058)
文摘Ag nanoparticles embedded in soda-lime silicate glass were fabricated by ion-exchange and subse-quently annealing method. Z-scan technique, femtosecond time-resolved optical Kerr effect (OKE) technique and femtosecond pump-probe experiment were used to investigate the effects of laser wavelength and laser pulse duration as well as annealing temperature on the third-order optical nonlinearity and ultrafast dynamics of the composites. It was found that the third-order susceptibility of Ag nanoparticles composite glass measured by 400 nm pulse source is larger than that measured by 800 nm pulse source due to an enhancement effect of local field near surface plasmon resonance of Ag nanoparticles in silicate glass. The third-order optical nonlinearity measured by ns laser source is about two orders of magnitude larger than that measured from fs pulse. The annealing temperature has an important effect on the third-order optical nonlinearity and ultrafast dynamics of the composites. Third-order nonlinear susceptibility up to 10?10 esu and fast relaxation process up to 0.2 ps have been obtained in Ag nanoparticles doped glass.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFE0134200)the National Natural Science Foundation of China(Grant Nos.12174147,91850114,11774131)+1 种基金the Natural Science Foundation of Jilin Province,China(Grant No.20220101016JC)the Open Research Fund of State Key Laboratory of Transient Optics and Photonics。
文摘By numerically solving the time-dependent Schr?dinger equation and employing the analytical perturbative model,we investigated the chirp-induced electron vortex in the photoionization of hydrogen atoms by a pair of counter-rotating circularly polarized chirped attosecond extremely ultraviolet pulses.We demonstrated that single-photon ionization of hydrogen atoms generates photoelectron momentum distributions(PMDs)with distinct helical vortex structures either with or without a time delay between two counter-rotating circularly polarized laser pulses.These structures are highly sensitive to both the time delay between the pulses and their chirp parameters.Our analytical model reveals that the splitting of vortex spirals is caused by the sign changing of the chirp-induced frequency-dependent time delay.We showed that to obtain the counterpart of the PMD under a pair of counter-rotating circularly polarized chirped pulses,both chirp parameters and ordering of pulses need to be reversed.
基金supported by the National Natural Science Foundation of China(Nos.52075284,52105195,51527901,and 11890672)the Postdoctoral Research Foundation of China(Nos.2020M680528 and BX2021151).
文摘About 30%of the world's primary energy consumption is in friction.The economic losses caused by friction energy dissipation and wear account for about 2%-7%of its gross domestic product(GDP)for different countries every year.The key to reducing energy consumption is to control the way of energy dissipation in the friction process.However,due to many various factors affecting friction and the lack of efficient detection methods,the energy dissipation mechanism in friction is still a challenging problem.Here,we firstly introduce the classical microscopic mechanism of friction energy dissipation,including phonon dissipation,electron dissipation,and non-contact friction energy dissipation.Then,we attempt to summarize the ultrafast friction energy dissipation and introduce the high-resolution friction energy dissipation detection system,since the origin of friction energy dissipation is essentially related to the ultrafast dynamics of excited electrons and phonons.Finally,the application of friction energy dissipation in representative high-end equipment is discussed,and the potential economic saving is predicted.
基金supported by the National Key R&D Program of China(2020YFA0308800 and 2021YFA1400100)the National Natural Science Foundation of China(12074212)+7 种基金supported by the National Natural Science Foundation of China(12174214 and 92065205)the National Key R&D Program of China(2018YFA0306504)the Innovation Program for Quantum Science and Technology(2021ZD0302100)supported by the National Natural Science Foundation of China(12274252)the National Key R&D Program of China(2018YFA0307100)supported by the National Natural Science Foundation of China(21975140 and 51991343)Fundamental Research Funds for the Central Universities(Buctrc202212)supported by funds from the University of Toronto。
基金Project supported by the National Key R&D Program of China (Grant Nos. 2022YFA1604402 and 2022YFA1604403)the National Natural Science Foundation of China (NSFC) (Grant No. 11721404)+3 种基金the Shanghai Rising-Star Program (Grant No. 21QA1406100)the Technology Innovation Action Plan of the Science and Technology Commission of Shanghai Municipality (Grant No. 20JC1416000)support by the Air Force Office of Scientific Research (AFOSR) (Grant No. FA9550-20-10139)the Texas A&M Engineering Experimental Station (TEES)
文摘With the integration of ultrafast reflectivity and polarimetry probes,we observed carrier relaxation and spin dynamics induced by ultrafast laser excitation of Ni(111)single crystals.The carrier relaxation time within the linear excitation range reveals that electron-phonon coupling and dissipation of photon energy into the bulk of the crystal take tens of picoseconds.On the other hand,the observed spin dynamics indicate a longer time of about 120 ps.To further understand how the lattice degree of freedom is coupled with these dynamics may require the integration of an ultrafast diffraction probe.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2023YFF0719200 and 2022YFA1404004)the National Natural Science Foundation of China(Grant Nos.62322115,61988102,61975110,62335012,and 12074248)+3 种基金111 Project(Grant No.D18014)the Key Project supported by Science and Technology Commission Shanghai Municipality(Grant No.YDZX20193100004960)Science and Technology Commission of Shanghai Municipality(Grant Nos.22JC1400200 and 21S31907400)General Administration of Customs People’s Republic of China(Grant No.2019HK006)。
文摘Chalcogenide superlattices Sb_(2)Te_(3)-GeTe is a candidate for interfacial phase-change memory(iPCM) data storage devices.By 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 superlattices.Sample 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 superlattices.By 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 coupling.These demonstrates play an important role in the development of iPCM-based high-speed optoelectronic devices.
基金supported by the National Key Research and Development Program of China(Nos.2021YFA1400700 and 2022YFA1404300)the National Natural Science Foundation of China(Nos.51925204,12022403,22003066,62375123,and 12375008)the Excellent Research Program of Nanjing University(No.ZYJH005).
文摘Plasmonics has aroused tremendous interest in photophysics,nanophotonics,and metamaterials.The extreme field concentration of plasmonics offers the ultimate spatial and temporal light control,single-particle detection,and optical modulation.Plasmon decay of metal nanostructures into hot carriers extends the application into photocatalysis,photodetectors,photovoltaics,and ultrafast nanooptics.The generated hot electron–hole pairs are transferred into adjacent dielectrics,well known to be more efficient than the hot carrier generation in dielectrics by direct photoexcitations.However,plasmon-induced hot-carrier-based devices are far from practical applications due to the low quantum yield of hot carrier extraction.Emergent challenges include low hot carrier generation efficiency in metals,rapid energy loss of hot carriers,and severe charge recombination at the metal/dielectric interface.In this review,we provide a fundamental insight into the hot carrier generation,transport,injection,and diffusion into dielectrics based on the steady-state and time-resolved spectroscopic studies as well as theoretical calculations.Strategies to enhance hot carrier generation in metals and electron transfer into dielectrics are discussed in detail.Then,applications based on hot carrier transfer are introduced briefly.Finally,we provide our suggestions on future research endeavors.We believe this review will provide a valuable overall physical picture of plasmon-induced hot carrier applications for researchers.
基金supported by the National Key R&D Program of China(2021YFA1400201,2022YFA1403504,2021YFB32003032021YFA1400502)+4 种基金the National Natural Science Foundation of China(T2188101,52025023,51991342,52021006,92163206,11888101,and 12374167)Guangdong Major Project of Basic and Applied Basic Research(2021B0301030002)the Strategic Priority Research Program of Chinese Academy of Sciences(XDB33000000)the Pearl River Talent Recruitment Program of Guangdong Province(2019ZT08C321)the New Cornerstone Science Foundation through the XPLORER PRIZE。
文摘Interlayer twist evokes revolutionary changes to the optical and electronic properties of twisted bilayer graphene(TBG)for electronics,photonics and optoelectronics.Although the ground state responses in TBG have been vastly and clearly studied,the dynamic process of its photoexcited carrier states mainly remains elusive.Here,we unveil the photoexcited hot carrier dynamics in TBG by time-resolved ultrafast photoluminescence(PL)autocorrelation spectroscopy.We demonstrate the unconventional ultrafast PL emission between the van Hove singularities(VHSs)with a~4 times prolonged relaxation lifetime.This intriguing photoexcited carrier behavior is ascribed to the abnormal hot carrier thermalization brought by bottleneck effects at VHSs and interlayer charge distribution process.Our study on hot carrier dynamics in TBG offers new insights into the excited states and correlated physics of graphene twistronics systems.
