Simultaneous metabolic and oxygen imaging is promising to follow up therapy response,dis-ease development and to determine prognostic factors.FLIM of metabolic coenzymes is now widely accepted to be the most reliable ...Simultaneous metabolic and oxygen imaging is promising to follow up therapy response,dis-ease development and to determine prognostic factors.FLIM of metabolic coenzymes is now widely accepted to be the most reliable method to determine cellular bioenergetics.Also,oxygen consumption has to be taken into account to understand treatment responses.The phosphorescence lifetimne of oxygen sensors is able to indicate local oxygen changes.For phosphorescence lifetime imaging(PLIM)dyes based on ruthenium(I)coordination com-plexes are useful,in detaill TLD1433 which possesses a variety of different triplet states,enables complex photochemistry and redox reactions.PLIM is usally reached by two photon exci-tation of the drug with a femtosecond(fs)pulsed Ti:Sapphire laser working at 80 MHz repe-tition rate and(time-correlated single photon counting)(TCSPC)detection electronics.The interesting question was whether it is possible to follow up PLIM 1using faster repetition rates.Faster repetition rates could be advantageous for the induction of specific photochemical reactions because of similar light doses used normally in standard CW light treatments.For this,a default 2p-FLIM-PLIM system was expanded by adding a second fs pulsed laser("helixx")which provides 50 fs pulses at a repetition rate of 250 MHz,more than 2.3 w average power and tunable from 720 nm to 920 nm.The laser beam was coupled into the AOM instead of the default 80 MHz laser.We demonstrated siuccessful applications of the 250 MHz laser for PLIM which correlates well with measurements done by excitation with the conventional 80MHx laser source.展开更多
BaFe_(12)O_(19)(BaM)thin films with thicknesses ranging from 15 nm–200 nm were deposited on Al_(2)O_(3)(0001)substrates by pulsed laser deposition(PLD).X-ray diffraction patterns show that a buffer layer with a thick...BaFe_(12)O_(19)(BaM)thin films with thicknesses ranging from 15 nm–200 nm were deposited on Al_(2)O_(3)(0001)substrates by pulsed laser deposition(PLD).X-ray diffraction patterns show that a buffer layer with a thickness of nearly 60 nm forms on the substrate,and then a c-axis perpendicularly oriented Ba M thin film grows on the buffer layer.Atomic force microscopy results indicate that the Ba M thin film exhibits a spiral island growth mode on the buffer layer.Magnetic hysteresis loop results confirm that the buffer layer exhibits no significant magnetic anisotropy,while the Ba M thin film exhibits perpendicular magnetic anisotropy.The out-of-plane coercivity decreases with increasing Ba M thin-film thickness due to the combined effect of grain size growth and lattice strain relaxation.The 200 nm thick film exhibits optimum magnetic properties with M_(s)=319 emu/cm^(3) and H_(c)=1546 Oe.展开更多
Pulsed laser ablation of soft biological tissue was studied at 10.6-, 2.94-, and 2.08-μm wavelengths. The ablation effects were assessed by means of optical microscope, the ablation crater depths were measured with r...Pulsed laser ablation of soft biological tissue was studied at 10.6-, 2.94-, and 2.08-μm wavelengths. The ablation effects were assessed by means of optical microscope, the ablation crater depths were measured with reading microscope. It was shown that Er：YAG laser produced the highest quality ablation with clear, sharp cuts following closely the spatial contour of the incident beam and the lowest fluence threshold. The pulsed CO2 laser presented the moderate quality ablation with the highest ablation efficiency. The craters drilled with Ho：YAG laser were generally larger than the incident laser beam spot, irregular in shape, and clearly dependent on the local morphology of biotissue. The ablation characteristics, including fluence threshold and ablation efficiency, varied substantially with wavelength. It is not evident that water is the only dominant chromophore in tissue.展开更多
Heavy ions and pulsed lasers are important means to simulate the ionization damage effects on semiconductor materials. The analytic solution of high-energy heavy ion energy loss in silicon has been obtained using the ...Heavy ions and pulsed lasers are important means to simulate the ionization damage effects on semiconductor materials. The analytic solution of high-energy heavy ion energy loss in silicon has been obtained using the Bethe-Bloch formula and the Kobetich-Katz theory, and some ionization damage parameters of Fe ions in silicon, such as the track structure and ionized charge density distribution, have been calculated and analyzed according to the theoretical calculation results. Using the Gaussian function and Beer＇s law, the parameters of the track structure and charge density distribution induced by a pulsed laser in silicon have also been calculated and compared with those of Fe ions in silicon, which provides a theoretical basis for ionization damage effect modeling.展开更多
Pulsed laser deposition(PLD),as an advanced synthesis technology with unparalleled control over thin films,has evolved into a universal platform for optoelectronic materials engineering.Its unique advantages including...Pulsed laser deposition(PLD),as an advanced synthesis technology with unparalleled control over thin films,has evolved into a universal platform for optoelectronic materials engineering.Its unique advantages including precise stoichiometric transfer,heterogeneous structure preparation and in-situ monitoring enable the design of opto-electrocatalysts with controllable active sites.Traditional methods struggle to pinpoint active sites in hydrogen technologies such as fuel cells and water electrolysis,impeding catalyst customization and mechanistic understanding.Nevertheless,PLD remains underused here despite its outstanding performances in targeted photo-assisted electrocatalysts design.This review systematically explores the breakthrough achievements and provides detailed insights into photo-enhanced water electrolysis and fuel cells based on PLD.Beginning with the fundamentals of epitaxial film growth and film classification,particularly emphasis the related in situ optical analysis techniques.It subsequently highlights recent advances in electro-oxidation and reduction reactions of H_(2)and O_(2),demonstrating the control capabilities of PLD in precisely correlating the structure and activity at the atomic level.Finally,the review concludes by proposing scalable fabrication strategies and performance optimization frameworks to bridge fundamental insights with industrial-scale optoelectronic integration systems.展开更多
The development of highly active and cost-effective catalysts for the full pH range of the hydrogen evolution reaction(HER)to meet the industrial application demands is an urgent challenge.In this work,the performance...The development of highly active and cost-effective catalysts for the full pH range of the hydrogen evolution reaction(HER)to meet the industrial application demands is an urgent challenge.In this work,the performance and structure–activityrelationships of CuIr alloys prepared by the pulsed laser ablation in liquid technique as full pH range HER catalysts wereinvestigated.Results indicated that Ir is doped into the Cu matrix as single atoms in CuIr-0.1,and CuIr-0.1 single-atom alloys(SAAs)exhibit superior HER performance and stability across the full pH range,with overpotentials of 135,203,and 172 mVat the current density of 10 mA/cm^(2)in acidic,neutral,and alkaline electrolytes,respectively.The enhanced performance ofCuIr-0.1 SAAs can be attributed to the abundant active sites and accelerated reaction kinetics brought about by the electroniceffects.This work successfully alloyed two immiscible metals to improve the catalytic performance,providing an avenue forthe development of highly efficient and versatile HER catalysts for industrial applications.展开更多
Type-II Dirac semimetal PtTe2is a promising candidate for various electronic device applications due to its high carrier mobility,high conductivity,and air stability.In this work,we report on the growth of large-scale...Type-II Dirac semimetal PtTe2is a promising candidate for various electronic device applications due to its high carrier mobility,high conductivity,and air stability.In this work,we report on the growth of large-scale PtTe_(2)films by the pulsed laser deposition(PLD)and the comparison of the magnetotransport properties with the PtTe2films grown by the chemical vapor deposition(CVD).The low-temperature Hall curves of the PLD-grown films exhibit a linear behavior,in contrast with the nonlinear characteristic of the Hall behavior observed in CVD-grown films,in which a defect gradient is introduced.Meanwhile,both PtTe2films show weak antilocalization at low temperatures,which is attributed to the strong spin–orbit coupling.展开更多
Avoiding crystallization while maintaining the original microstructure and mechanical properties of the material are long-term goals of laser welding of Zr-based bulk metallic glass(BMG).In this paper,the effect of pu...Avoiding crystallization while maintaining the original microstructure and mechanical properties of the material are long-term goals of laser welding of Zr-based bulk metallic glass(BMG).In this paper,the effect of pulsed laser welding parameters on the microstructure,crystallization degree,and mechanical properties of Zr57Nb5Cu15.4Ni12.6Al10 BMG is investigated.Non-crystallized welding forming of a zirconium-based amorphous alloy is achieved by optimizing the process parameters of pulsed laser welding.The crystallization degree of Zr-based BMG is mainly determined by the welding speed and power.The welding depth and crystallization area fraction increase with an increase in the effective peak power density.The optimized welding process can effectively reduce the heat accumulation of the weld,thus avoiding crystallization.The flexural strength of the weld can be maintained at 96.5%of the matrix.展开更多
Pulsed laser welding was used in joining pure aluminum to stainless steel in a lap joint configuration. It is found that the mechanical properties of the laser joints were closely correlated with the bead geometry, i....Pulsed laser welding was used in joining pure aluminum to stainless steel in a lap joint configuration. It is found that the mechanical properties of the laser joints were closely correlated with the bead geometry, i.e., penetration depth. In order to study the correlation, two typical laser welds with different penetration depths were analyzed. In high penetration depth (354 μm) joint, Al-rich Fe?Al IMCs with microcracks were formed at the Al/fusion zone (FZ) interface. The joint strength was found to be (27.2±1.7) N/mm and three failure modes were observed near the Al/FZ interface. In low penetration depth (108 μm) joint, Fe-rich Fe?Al IMCs without any defect were formed at the Al/FZ interface. The joint strength was found to be (46.2±1.9) N/mm and one failure mode was observed across the FZ.展开更多
Based on the kinetic theoretical Vlasov-Poisson equation, a surface Coulomb explosion model of SiO2 material induced by ultra-short pulsed laser radiation is established. The non-equilibrium free electron distribution...Based on the kinetic theoretical Vlasov-Poisson equation, a surface Coulomb explosion model of SiO2 material induced by ultra-short pulsed laser radiation is established. The non-equilibrium free electron distribution resulting from the two mechanisms of multi-photon ionization and avalanche ionization is computed. A quantitative analysis is given to describe the Coulomb explosion induced by the self-consistent electric field, and the impact of the parameters of laser pulses on the surface ablation is also discussed. The results show that the electron relaxation time is not constant, but it is related to the microscopic state of the electrons, so the relaxation time approximation is not available on the femtosecond time scale. The ablation depths computed by the theoretical model are in good agreement with the experimental results in the range of pulse durations from 0 to 1 ps.展开更多
Amorphous metal-based catalysts are highly promising for water splitting due to their abundance of unsaturated active sites.Herein,we report a one-step,surfactant-free synthesis of amorphous nickel nanoparticles(NPs)e...Amorphous metal-based catalysts are highly promising for water splitting due to their abundance of unsaturated active sites.Herein,we report a one-step,surfactant-free synthesis of amorphous nickel nanoparticles(NPs)encapsulated in nitrogen-doped carbon shells(A-Ni@NC)via pulsed laser ablation in liquid(PLAL).The synergistic integration of the amorphous Ni core and a defect-rich N-doped carbon shell markedly enhanced the catalytic activities for both the hydrogen evolution reaction(HER)and oxygen evolution reaction(OER),with low overpotentials of 182 mV for HER and 288 mV for OER at 10 mA cm^(-2)in 1.0 m KOH.Furthermore,the bifunctional catalyst achieved a current density of 10 mA cm^(-2)at 1.63 V and retained 98.9%of its initial performance after 100 h of operation.The nitrogen-rich carbon shell not only offered abundant active sites and structural protection but also promoted charge transport.Density functional theory(DFT)calculations revealed that N-doping optimized intermediate adsorption energies,while the amorphous Ni core facilitated efficient electron transfer.This green and scalable synthesis strategy provides a promising platform for developing a wide range of transition metal@N-doped carbon hybrid catalysts for sustainable energy conversion applications.展开更多
This paper quantitatively discusses the influence of well contact on single-event transient(SET)in sub-20 nm FinFET by two-photon absorption(TPA)pulse laser.Two groups of inverter chains were designed to investigate t...This paper quantitatively discusses the influence of well contact on single-event transient(SET)in sub-20 nm FinFET by two-photon absorption(TPA)pulse laser.Two groups of inverter chains were designed to investigate the impact of well contact distance on the FinFET process.The experimental results show that the SET pulse width has a bimodal symmetric distribution,which is different from that of a bulk planar CMOS device.To investigate the detailed mechanism of the phenomenon,a high-precision FinFET TCAD model was established,in which both Id-Vd and Id-Vg errors were less than 10%compared to the SPICE model provided by the commercial process.TCAD simulation under heavy ion injection showed the mechanism of the abnormal phenomenon,where the well contact plays a major role in charge collection at the near-well contact distance,while the source plays a major role at the far distance.This phenomenon is completely different from that of planar CMOS devices.This indicates that the SET mechanism becomes more complicated during the FinFET process.Therefore,more effective SET hardening methods should be investigated for FinFET.展开更多
Understanding the complex plasma dynamics in ultra-intense relativistic laser-solid interactions is of fundamental importance for applications of laser-plasma-based particle accelerators,the creation of high-energy-de...Understanding the complex plasma dynamics in ultra-intense relativistic laser-solid interactions is of fundamental importance for applications of laser-plasma-based particle accelerators,the creation of high-energy-density matter,understanding planetary science,and laser-driven fusion energy.However,experimental efforts in this regime have been limited by the lack of accessibility of over-critical densities and the poor spatiotemporal resolution of conventional diagnostics.Over the last decade,the advent of femtosecond brilliant hard X-ray free-electron lasers(XFELs)has opened new horizons to overcome these limitations.Here,for the first time,we present full-scale spatiotemporal measurements of solid-density plasma dynamics,including preplasma generation with tens of nanometer scale length driven by the leading edge of a relativistic laser pulse,ultrafast heating and ionization at the main pulse arrival,the laser-driven blast wave,and transient surface return current-induced compression dynamics up to hundreds of picoseconds after interaction.These observations are enabled by utilizing a novel combination of advanced X-ray diagnostics including small-angle X-ray scattering,resonant X-ray emission spectroscopy,and propagation-based X-ray phase-contrast imaging simultaneously at the European XFEL-HED beamline station.展开更多
Experiments with interacting high-velocity flows in a laser plasma can help answer fundamental questions in plasma physics and improve understanding of the mechanisms behind some astrophysical phenomena,such as the fo...Experiments with interacting high-velocity flows in a laser plasma can help answer fundamental questions in plasma physics and improve understanding of the mechanisms behind some astrophysical phenomena,such as the formation of collisionless shock waves,deceleration of accretion flows,and evolution of solar and stellar flares.This work presents the first direct experimental observations of stagnation and redirection of counterstreaming flows(jets)of laser plasma induced by intense laser pulses with intensity I~2×10^(18) W/cm^(2).Hybrid particlein-cell-fluid modeling,which takes into account the kinetic effects of ion motion and the evolution of the pressure tensor for electrons,demonstrates the compression of counterdirected toroidal self-generated magnetic fields embedded in counterstreaming plasma flows.The enhancement of the toroidal magnetic field in the interaction region results in plasma flow stagnation and redirection of the jets across the line of their initial propagation.展开更多
Chemical vapor deposited （CVD） diamond film has broad application foreground in high-tech fields. But polycrystalline CVD self-standing diamond thick film has rough surface and non-uniform thickness that adversely a...Chemical vapor deposited （CVD） diamond film has broad application foreground in high-tech fields. But polycrystalline CVD self-standing diamond thick film has rough surface and non-uniform thickness that adversely affect its extensive applications. Laser polishing is a useful method to smooth self-standing diamond film. At present, attentions have been focused on experimental research on laser polishing, but the revealing of theoretical model and the forecast of polishing process are vacant. The paper presents a finite element model to simulate and analyze the mechanism of laser polishing diamond based on laser thermal conduction theory. The experimental investigation is also carried out on Nd：YAG pulsed laser smoothing diamond thick film. The simulation results have good accordance with the results of experimental results. The temperature and thermal stress fields are investigated at different incidence angles and parameters of Nd：YAG pulsed laser. The pyramidal-like roughness of diamond thick film leads to the non-homogeneous temperature fields. The temperature at the peak of diamond film is much higher than that in the valley, which leads to the smoothing of diamond thick film. The effect of laser parameters on the surface roughness and thickness of graphite transition layer is also carried out. The results show that high power density laser makes the diamond surface rapid heating, evaporation and sublimation after its graphitization. It is also found that the good polish quality of diamond thick film can be obtained by a combination of large incident angle, moderate laser pulsed energy, large repetition rate and moderate laser pulse width. The results obtained here provide the theoretical basis for laser polishing diamond film with high efficiency and high quality.展开更多
Effects of laser pulse distance and reinforcing of 5456 aluminum alloy were investigated on laser weldability of Al alloy to duplex stainless steel (DSS) plates. The aluminum alloy plate was reinforced by nickel-base ...Effects of laser pulse distance and reinforcing of 5456 aluminum alloy were investigated on laser weldability of Al alloy to duplex stainless steel (DSS) plates. The aluminum alloy plate was reinforced by nickel-base BNi-2 brazing powder via friction stir processing. The DSS plates were laser welded to the Al5456/BNi-2 composite and also to the Al5456 alloy plates. The welding zones were studied by scanning electron microscopy, X-ray diffractometry, micro-hardness and shear tests. The weld interface layer became thinner from 23 to 5 μm, as the laser pulse distance was increased from 0.2 to 0.5 mm. Reinforcing of the Al alloy modified the phases at interface layer from Al-Fe intermetallic compounds (IMCs) in the DSS/Al alloy weld, to Al-Ni-Fe IMCs in the DSS/Al composite one, since more nickel was injected in the weld pool by BNi-2 reinforcements. This led to a remarkable reduction in crack tendency of the welds and decreased the hardness of the interface layer from ~950 HV to ~600 HV. Shear strengths of the DSS/Al composite welds were significantly increased by ~150%, from 46 to 114 MPa, in comparison to the DSS/Al alloy ones.展开更多
Based on the extended application of COMSOL multiphysics, a novel dual heat source model for pulsed laser-gas tungsten arc （GTA） hybrid welding was established. This model successfully solved the problem of simulati...Based on the extended application of COMSOL multiphysics, a novel dual heat source model for pulsed laser-gas tungsten arc （GTA） hybrid welding was established. This model successfully solved the problem of simulation inaccuracy caused by energy superposition effect between laser and arc due to their different physical characteristics. Numerical simulation for pulsed laser-GTA hybrid welding of magnesium alloy process was conducted, and the simulation indicated good agree- ments with the measured thermal cycle curve and the shape of weld beads. Effects of pulse laser parameters （laser-excited current, pulse duration, and pulse frequency） on the temperature field and weld pool morphology were investigated. The experimental and simulation results suggest that when the laser pulse energy keeps constant, welding efficiency of the hybrid heat source is increased by increasing laser current or decreasing pulse duration due to the increased ratio of the weld bead depth to width. With large laser currents, severe spatters tend to occur. For optimized welding process, the laser current should be controlled in the range of 150-175 A, the pulse duration should be longer than 1 ms, and the pulse frequency should be equal to or slightly greater than 20 Hz.展开更多
Polycrystalline ZnS films were prepared by pulsed laser deposition （PLD） on quartz glass substrates under different growth conditions at different substrate temperatures of 20, 200, 400, and 600 ℃, which is a suita...Polycrystalline ZnS films were prepared by pulsed laser deposition （PLD） on quartz glass substrates under different growth conditions at different substrate temperatures of 20, 200, 400, and 600 ℃, which is a suitable alternative to chemical bath deposited （CBD） CdS as a buffer layer in Cu（In,Ga）Se2 （CIGS） solar cells. X-ray diffraction studies indicate the films are polycrystalline with zinc-blende structure and they exhibit preferential orientation along the cubic phase β-ZnS （111） direction, which conflicts with the conclusion of wurtzite structure by Murali that the ZnS films deposited by pulse plating technique was polycrystalline with wurtzite structure. The Raman spectra of grown films show Al mode at approximately 350 cm^-1, generally observed in the cubic phase β-ZnS compounds. The planar and the cross-sectional morphology were observed by scanning electron microscopic. The dense, smooth, uniform grains are formed on the quartz glass substrates through PLD technique. The grain size of ZnS deposited by PLD is much smaller than that of CdS by conventional CBD method, which is analyzed as the main reason of detrimental cell performance. The composition of the ZnS films was also measured by X-ray fluorescence. The typical ZnS films obtained in this work are near stoichiometric and only a small amount of S-rich. The energy band gaps at different temperatures were obtained by absorption spectroscopy measurement, which increases from 3.2 eV to 3.7 eV with the increasing of the deposition temperature. ZnS has a wider energy band gap than CdS （2.4 eV）, which can enhance the blue response of the photovoltaic cells. These results show the high-quality of these substitute buffer layer materials are prepared through an all-dry technology, which can be used in the manufacture of CIGS thin film solar cells.展开更多
The flat plane of small surface roughness below 0.1μm average roughness was obtained for monocrystalline diamond by nanosecond pulsed laser irradiation of 1060 nm and post-process acid cleaning,at a laser fluence aro...The flat plane of small surface roughness below 0.1μm average roughness was obtained for monocrystalline diamond by nanosecond pulsed laser irradiation of 1060 nm and post-process acid cleaning,at a laser fluence around the material removal threshold value.The glossy and flat plane at the bottom of the micro-groove was parallel to the top surface of the specimen,although the round beam of Gaussian mode was irradiated in the direction perpendicular to the top surface of specimen.The square beam of top-hat mode produced a shallower micro-groove with a wider,flatter bottom compared with the round beam in Gaussian mode.The creation method of the flat plane with small surface roughness was discussed in the arrangement strategy of linear micro-grooving by the square beam of top-hat mode.Normal side-by-side repetition of linear micro-grooving did not create a flat plane with constant depth.Therefore,a two-step scanning method was proposed in order to overcome the problem in the normal side-by-side repetition of liner micro-grooving.Non-removal areas were partly retained between the processing lines in the first step,and the laser scanning was conducted on the retained area in the second step.The newly proposed two-step scanning method was practical and useful to create a widely flat plane with small surface roughness,and the two-step scanning method provided superior control over the micro-groove depth.This proposed method can reduce the surface roughness in addition to the shape creation of monocrystalline diamond,and it can be used as a high-quality micro-shape fabrication method of monocrystalline diamond.展开更多
Functionalized implants demonstrate an upgraded approach in orthopedic implants,aiming to achieve long term success through improved bio integration.Bioceramic coatings with multifunctionality have arisen as an effect...Functionalized implants demonstrate an upgraded approach in orthopedic implants,aiming to achieve long term success through improved bio integration.Bioceramic coatings with multifunctionality have arisen as an effective substitute for conventional coatings,owing to their combination of various properties that are essential for bio-implants,such as osteointegration and antibacterial character.In the present study,thin hopeite coatings were produced by Pulsed laser deposition(PLD)and radio frequency magnetron sputtering(RFMS)on Ti64 substrates.The obtained hopeite coatings were annealed at 500°C in ambient air and studied in terms of surface morphology,phase composition,surface roughness,adhesion strength,antibacterial efficacy,apatite forming ability,and surface wettability by scanning electron microscope(SEM),X-ray diffraction(XRD),atomic force microscope(AFM),tensometer,fluorescence-activated cell sorting(FACS),simulated body fluid(SBF)immersion test and contact angle goniometer,respectively.Furthermore,based on promising results obtained in the present work it can be summarized that the new generation multifunctional hopeite coating synthesized by two alternative new process routes of PLD and RFMS on Ti64 substrates,provides effective alternatives to conventional coatings,largely attributed to strong osteointegration and antibacterial character of deposited hopeite coating ensuring the overall stability of metallic orthopedic implants.展开更多
基金supported by the Ministry of Research and Development,FKZ order:13N14508("OMOXI")by the Ministry of Economics,ZIM-Project,FKZ:ZF4322901RE6("UFEMPU").
文摘Simultaneous metabolic and oxygen imaging is promising to follow up therapy response,dis-ease development and to determine prognostic factors.FLIM of metabolic coenzymes is now widely accepted to be the most reliable method to determine cellular bioenergetics.Also,oxygen consumption has to be taken into account to understand treatment responses.The phosphorescence lifetimne of oxygen sensors is able to indicate local oxygen changes.For phosphorescence lifetime imaging(PLIM)dyes based on ruthenium(I)coordination com-plexes are useful,in detaill TLD1433 which possesses a variety of different triplet states,enables complex photochemistry and redox reactions.PLIM is usally reached by two photon exci-tation of the drug with a femtosecond(fs)pulsed Ti:Sapphire laser working at 80 MHz repe-tition rate and(time-correlated single photon counting)(TCSPC)detection electronics.The interesting question was whether it is possible to follow up PLIM 1using faster repetition rates.Faster repetition rates could be advantageous for the induction of specific photochemical reactions because of similar light doses used normally in standard CW light treatments.For this,a default 2p-FLIM-PLIM system was expanded by adding a second fs pulsed laser("helixx")which provides 50 fs pulses at a repetition rate of 250 MHz,more than 2.3 w average power and tunable from 720 nm to 920 nm.The laser beam was coupled into the AOM instead of the default 80 MHz laser.We demonstrated siuccessful applications of the 250 MHz laser for PLIM which correlates well with measurements done by excitation with the conventional 80MHx laser source.
文摘BaFe_(12)O_(19)(BaM)thin films with thicknesses ranging from 15 nm–200 nm were deposited on Al_(2)O_(3)(0001)substrates by pulsed laser deposition(PLD).X-ray diffraction patterns show that a buffer layer with a thickness of nearly 60 nm forms on the substrate,and then a c-axis perpendicularly oriented Ba M thin film grows on the buffer layer.Atomic force microscopy results indicate that the Ba M thin film exhibits a spiral island growth mode on the buffer layer.Magnetic hysteresis loop results confirm that the buffer layer exhibits no significant magnetic anisotropy,while the Ba M thin film exhibits perpendicular magnetic anisotropy.The out-of-plane coercivity decreases with increasing Ba M thin-film thickness due to the combined effect of grain size growth and lattice strain relaxation.The 200 nm thick film exhibits optimum magnetic properties with M_(s)=319 emu/cm^(3) and H_(c)=1546 Oe.
基金This work was supported by the National Natural Science Foundation of China (No.60578057)the Fujian Provincial Education Scientific Project (No.JAO50217/JB06108).
文摘Pulsed laser ablation of soft biological tissue was studied at 10.6-, 2.94-, and 2.08-μm wavelengths. The ablation effects were assessed by means of optical microscope, the ablation crater depths were measured with reading microscope. It was shown that Er：YAG laser produced the highest quality ablation with clear, sharp cuts following closely the spatial contour of the incident beam and the lowest fluence threshold. The pulsed CO2 laser presented the moderate quality ablation with the highest ablation efficiency. The craters drilled with Ho：YAG laser were generally larger than the incident laser beam spot, irregular in shape, and clearly dependent on the local morphology of biotissue. The ablation characteristics, including fluence threshold and ablation efficiency, varied substantially with wavelength. It is not evident that water is the only dominant chromophore in tissue.
基金Supported by Foundation of the National Laboratory of Vacuum & Cryogenics Technology and Physics (9140C5503070803)
文摘Heavy ions and pulsed lasers are important means to simulate the ionization damage effects on semiconductor materials. The analytic solution of high-energy heavy ion energy loss in silicon has been obtained using the Bethe-Bloch formula and the Kobetich-Katz theory, and some ionization damage parameters of Fe ions in silicon, such as the track structure and ionized charge density distribution, have been calculated and analyzed according to the theoretical calculation results. Using the Gaussian function and Beer＇s law, the parameters of the track structure and charge density distribution induced by a pulsed laser in silicon have also been calculated and compared with those of Fe ions in silicon, which provides a theoretical basis for ionization damage effect modeling.
基金supported by the Youth Project of the National Natural Science Foundation of China(Grant No.22402024)the Postdoctoral Innovation Talents Support Program of China(Grant No.BX20230061)the Natural Science Foundation of Sichuan(Grant No.25QNJJ3094).P.M.-B.acknowledges funding from Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)under Germany's Excellence Strategy-EXC 2089/1-390776260(e conversion).
文摘Pulsed laser deposition(PLD),as an advanced synthesis technology with unparalleled control over thin films,has evolved into a universal platform for optoelectronic materials engineering.Its unique advantages including precise stoichiometric transfer,heterogeneous structure preparation and in-situ monitoring enable the design of opto-electrocatalysts with controllable active sites.Traditional methods struggle to pinpoint active sites in hydrogen technologies such as fuel cells and water electrolysis,impeding catalyst customization and mechanistic understanding.Nevertheless,PLD remains underused here despite its outstanding performances in targeted photo-assisted electrocatalysts design.This review systematically explores the breakthrough achievements and provides detailed insights into photo-enhanced water electrolysis and fuel cells based on PLD.Beginning with the fundamentals of epitaxial film growth and film classification,particularly emphasis the related in situ optical analysis techniques.It subsequently highlights recent advances in electro-oxidation and reduction reactions of H_(2)and O_(2),demonstrating the control capabilities of PLD in precisely correlating the structure and activity at the atomic level.Finally,the review concludes by proposing scalable fabrication strategies and performance optimization frameworks to bridge fundamental insights with industrial-scale optoelectronic integration systems.
基金supported by the Natural Science Foundation of China(Nos.52022064 and 51971154).
文摘The development of highly active and cost-effective catalysts for the full pH range of the hydrogen evolution reaction(HER)to meet the industrial application demands is an urgent challenge.In this work,the performance and structure–activityrelationships of CuIr alloys prepared by the pulsed laser ablation in liquid technique as full pH range HER catalysts wereinvestigated.Results indicated that Ir is doped into the Cu matrix as single atoms in CuIr-0.1,and CuIr-0.1 single-atom alloys(SAAs)exhibit superior HER performance and stability across the full pH range,with overpotentials of 135,203,and 172 mVat the current density of 10 mA/cm^(2)in acidic,neutral,and alkaline electrolytes,respectively.The enhanced performance ofCuIr-0.1 SAAs can be attributed to the abundant active sites and accelerated reaction kinetics brought about by the electroniceffects.This work successfully alloyed two immiscible metals to improve the catalytic performance,providing an avenue forthe development of highly efficient and versatile HER catalysts for industrial applications.
基金Project supported by the National Key R&D Program of China(Grant No.2022YFA1402404)the National Natural Science Foundation of China(Grant Nos.T2394473,624B2070,and 62274085)。
文摘Type-II Dirac semimetal PtTe2is a promising candidate for various electronic device applications due to its high carrier mobility,high conductivity,and air stability.In this work,we report on the growth of large-scale PtTe_(2)films by the pulsed laser deposition(PLD)and the comparison of the magnetotransport properties with the PtTe2films grown by the chemical vapor deposition(CVD).The low-temperature Hall curves of the PLD-grown films exhibit a linear behavior,in contrast with the nonlinear characteristic of the Hall behavior observed in CVD-grown films,in which a defect gradient is introduced.Meanwhile,both PtTe2films show weak antilocalization at low temperatures,which is attributed to the strong spin–orbit coupling.
基金Supported by Guangdong Major Project of Basic and Applied Research,China(Grant No.2019B030302010)National Natural Science Foundation of China (Grant Nos.51735003,52205456)
文摘Avoiding crystallization while maintaining the original microstructure and mechanical properties of the material are long-term goals of laser welding of Zr-based bulk metallic glass(BMG).In this paper,the effect of pulsed laser welding parameters on the microstructure,crystallization degree,and mechanical properties of Zr57Nb5Cu15.4Ni12.6Al10 BMG is investigated.Non-crystallized welding forming of a zirconium-based amorphous alloy is achieved by optimizing the process parameters of pulsed laser welding.The crystallization degree of Zr-based BMG is mainly determined by the welding speed and power.The welding depth and crystallization area fraction increase with an increase in the effective peak power density.The optimized welding process can effectively reduce the heat accumulation of the weld,thus avoiding crystallization.The flexural strength of the weld can be maintained at 96.5%of the matrix.
基金Project(51265035)supported by the National Natural Science Foundation of ChinaProject(20151BAB206042)supported by the Natural Science Foundation of Jiangxi Province,ChinaProject(GJJ150020)supported by the Jiangxi Provincial Department of Education,China
文摘Pulsed laser welding was used in joining pure aluminum to stainless steel in a lap joint configuration. It is found that the mechanical properties of the laser joints were closely correlated with the bead geometry, i.e., penetration depth. In order to study the correlation, two typical laser welds with different penetration depths were analyzed. In high penetration depth (354 μm) joint, Al-rich Fe?Al IMCs with microcracks were formed at the Al/fusion zone (FZ) interface. The joint strength was found to be (27.2±1.7) N/mm and three failure modes were observed near the Al/FZ interface. In low penetration depth (108 μm) joint, Fe-rich Fe?Al IMCs without any defect were formed at the Al/FZ interface. The joint strength was found to be (46.2±1.9) N/mm and one failure mode was observed across the FZ.
文摘Based on the kinetic theoretical Vlasov-Poisson equation, a surface Coulomb explosion model of SiO2 material induced by ultra-short pulsed laser radiation is established. The non-equilibrium free electron distribution resulting from the two mechanisms of multi-photon ionization and avalanche ionization is computed. A quantitative analysis is given to describe the Coulomb explosion induced by the self-consistent electric field, and the impact of the parameters of laser pulses on the surface ablation is also discussed. The results show that the electron relaxation time is not constant, but it is related to the microscopic state of the electrons, so the relaxation time approximation is not available on the femtosecond time scale. The ablation depths computed by the theoretical model are in good agreement with the experimental results in the range of pulse durations from 0 to 1 ps.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(NRF-2023R1A2C1005419).
文摘Amorphous metal-based catalysts are highly promising for water splitting due to their abundance of unsaturated active sites.Herein,we report a one-step,surfactant-free synthesis of amorphous nickel nanoparticles(NPs)encapsulated in nitrogen-doped carbon shells(A-Ni@NC)via pulsed laser ablation in liquid(PLAL).The synergistic integration of the amorphous Ni core and a defect-rich N-doped carbon shell markedly enhanced the catalytic activities for both the hydrogen evolution reaction(HER)and oxygen evolution reaction(OER),with low overpotentials of 182 mV for HER and 288 mV for OER at 10 mA cm^(-2)in 1.0 m KOH.Furthermore,the bifunctional catalyst achieved a current density of 10 mA cm^(-2)at 1.63 V and retained 98.9%of its initial performance after 100 h of operation.The nitrogen-rich carbon shell not only offered abundant active sites and structural protection but also promoted charge transport.Density functional theory(DFT)calculations revealed that N-doping optimized intermediate adsorption energies,while the amorphous Ni core facilitated efficient electron transfer.This green and scalable synthesis strategy provides a promising platform for developing a wide range of transition metal@N-doped carbon hybrid catalysts for sustainable energy conversion applications.
基金supported by Natural Science Foundation of China(Nos.62174180 and 62304258)National Key R&D Program of China(No.2023YFA1609000)。
文摘This paper quantitatively discusses the influence of well contact on single-event transient(SET)in sub-20 nm FinFET by two-photon absorption(TPA)pulse laser.Two groups of inverter chains were designed to investigate the impact of well contact distance on the FinFET process.The experimental results show that the SET pulse width has a bimodal symmetric distribution,which is different from that of a bulk planar CMOS device.To investigate the detailed mechanism of the phenomenon,a high-precision FinFET TCAD model was established,in which both Id-Vd and Id-Vg errors were less than 10%compared to the SPICE model provided by the commercial process.TCAD simulation under heavy ion injection showed the mechanism of the abnormal phenomenon,where the well contact plays a major role in charge collection at the near-well contact distance,while the source plays a major role at the far distance.This phenomenon is completely different from that of planar CMOS devices.This indicates that the SET mechanism becomes more complicated during the FinFET process.Therefore,more effective SET hardening methods should be investigated for FinFET.
基金funding from Grant No. HIDSS-0002 DASHH (Data Science in Hamburg-Helmholtz Graduate School for the Structure of Matter)partially supported by the Helmholtz Imaging platform through the project “Smart Phase.”
文摘Understanding the complex plasma dynamics in ultra-intense relativistic laser-solid interactions is of fundamental importance for applications of laser-plasma-based particle accelerators,the creation of high-energy-density matter,understanding planetary science,and laser-driven fusion energy.However,experimental efforts in this regime have been limited by the lack of accessibility of over-critical densities and the poor spatiotemporal resolution of conventional diagnostics.Over the last decade,the advent of femtosecond brilliant hard X-ray free-electron lasers(XFELs)has opened new horizons to overcome these limitations.Here,for the first time,we present full-scale spatiotemporal measurements of solid-density plasma dynamics,including preplasma generation with tens of nanometer scale length driven by the leading edge of a relativistic laser pulse,ultrafast heating and ionization at the main pulse arrival,the laser-driven blast wave,and transient surface return current-induced compression dynamics up to hundreds of picoseconds after interaction.These observations are enabled by utilizing a novel combination of advanced X-ray diagnostics including small-angle X-ray scattering,resonant X-ray emission spectroscopy,and propagation-based X-ray phase-contrast imaging simultaneously at the European XFEL-HED beamline station.
基金supported by Russian Science Foundation Grant No.24-62-00032.
文摘Experiments with interacting high-velocity flows in a laser plasma can help answer fundamental questions in plasma physics and improve understanding of the mechanisms behind some astrophysical phenomena,such as the formation of collisionless shock waves,deceleration of accretion flows,and evolution of solar and stellar flares.This work presents the first direct experimental observations of stagnation and redirection of counterstreaming flows(jets)of laser plasma induced by intense laser pulses with intensity I~2×10^(18) W/cm^(2).Hybrid particlein-cell-fluid modeling,which takes into account the kinetic effects of ion motion and the evolution of the pressure tensor for electrons,demonstrates the compression of counterdirected toroidal self-generated magnetic fields embedded in counterstreaming plasma flows.The enhancement of the toroidal magnetic field in the interaction region results in plasma flow stagnation and redirection of the jets across the line of their initial propagation.
基金supported by National Natural Science Foundation of China (Grant No. 51005117)Graduate Innovation Fund of Nanjing University of Aeronautics and Astronautics,China (Grant No.KFJJ20110223)Priority Academic Program Development of Jiangsu Higher Education Institutions of China (PAPD)
文摘Chemical vapor deposited （CVD） diamond film has broad application foreground in high-tech fields. But polycrystalline CVD self-standing diamond thick film has rough surface and non-uniform thickness that adversely affect its extensive applications. Laser polishing is a useful method to smooth self-standing diamond film. At present, attentions have been focused on experimental research on laser polishing, but the revealing of theoretical model and the forecast of polishing process are vacant. The paper presents a finite element model to simulate and analyze the mechanism of laser polishing diamond based on laser thermal conduction theory. The experimental investigation is also carried out on Nd：YAG pulsed laser smoothing diamond thick film. The simulation results have good accordance with the results of experimental results. The temperature and thermal stress fields are investigated at different incidence angles and parameters of Nd：YAG pulsed laser. The pyramidal-like roughness of diamond thick film leads to the non-homogeneous temperature fields. The temperature at the peak of diamond film is much higher than that in the valley, which leads to the smoothing of diamond thick film. The effect of laser parameters on the surface roughness and thickness of graphite transition layer is also carried out. The results show that high power density laser makes the diamond surface rapid heating, evaporation and sublimation after its graphitization. It is also found that the good polish quality of diamond thick film can be obtained by a combination of large incident angle, moderate laser pulsed energy, large repetition rate and moderate laser pulse width. The results obtained here provide the theoretical basis for laser polishing diamond film with high efficiency and high quality.
文摘Effects of laser pulse distance and reinforcing of 5456 aluminum alloy were investigated on laser weldability of Al alloy to duplex stainless steel (DSS) plates. The aluminum alloy plate was reinforced by nickel-base BNi-2 brazing powder via friction stir processing. The DSS plates were laser welded to the Al5456/BNi-2 composite and also to the Al5456 alloy plates. The welding zones were studied by scanning electron microscopy, X-ray diffractometry, micro-hardness and shear tests. The weld interface layer became thinner from 23 to 5 μm, as the laser pulse distance was increased from 0.2 to 0.5 mm. Reinforcing of the Al alloy modified the phases at interface layer from Al-Fe intermetallic compounds (IMCs) in the DSS/Al alloy weld, to Al-Ni-Fe IMCs in the DSS/Al composite one, since more nickel was injected in the weld pool by BNi-2 reinforcements. This led to a remarkable reduction in crack tendency of the welds and decreased the hardness of the interface layer from ~950 HV to ~600 HV. Shear strengths of the DSS/Al composite welds were significantly increased by ~150%, from 46 to 114 MPa, in comparison to the DSS/Al alloy ones.
基金This work was supported by the Natural Science Foundation of Liaoning Province of China （Grant Nos. 201602391 and 20170540460）.
文摘Based on the extended application of COMSOL multiphysics, a novel dual heat source model for pulsed laser-gas tungsten arc （GTA） hybrid welding was established. This model successfully solved the problem of simulation inaccuracy caused by energy superposition effect between laser and arc due to their different physical characteristics. Numerical simulation for pulsed laser-GTA hybrid welding of magnesium alloy process was conducted, and the simulation indicated good agree- ments with the measured thermal cycle curve and the shape of weld beads. Effects of pulse laser parameters （laser-excited current, pulse duration, and pulse frequency） on the temperature field and weld pool morphology were investigated. The experimental and simulation results suggest that when the laser pulse energy keeps constant, welding efficiency of the hybrid heat source is increased by increasing laser current or decreasing pulse duration due to the increased ratio of the weld bead depth to width. With large laser currents, severe spatters tend to occur. For optimized welding process, the laser current should be controlled in the range of 150-175 A, the pulse duration should be longer than 1 ms, and the pulse frequency should be equal to or slightly greater than 20 Hz.
基金ACKNOWLEDGMENTS This work was supported by the National Basic Research Program of China （No.2006CB92200） and the National Natural Science Foundation of China （No.10774136）.
文摘Polycrystalline ZnS films were prepared by pulsed laser deposition （PLD） on quartz glass substrates under different growth conditions at different substrate temperatures of 20, 200, 400, and 600 ℃, which is a suitable alternative to chemical bath deposited （CBD） CdS as a buffer layer in Cu（In,Ga）Se2 （CIGS） solar cells. X-ray diffraction studies indicate the films are polycrystalline with zinc-blende structure and they exhibit preferential orientation along the cubic phase β-ZnS （111） direction, which conflicts with the conclusion of wurtzite structure by Murali that the ZnS films deposited by pulse plating technique was polycrystalline with wurtzite structure. The Raman spectra of grown films show Al mode at approximately 350 cm^-1, generally observed in the cubic phase β-ZnS compounds. The planar and the cross-sectional morphology were observed by scanning electron microscopic. The dense, smooth, uniform grains are formed on the quartz glass substrates through PLD technique. The grain size of ZnS deposited by PLD is much smaller than that of CdS by conventional CBD method, which is analyzed as the main reason of detrimental cell performance. The composition of the ZnS films was also measured by X-ray fluorescence. The typical ZnS films obtained in this work are near stoichiometric and only a small amount of S-rich. The energy band gaps at different temperatures were obtained by absorption spectroscopy measurement, which increases from 3.2 eV to 3.7 eV with the increasing of the deposition temperature. ZnS has a wider energy band gap than CdS （2.4 eV）, which can enhance the blue response of the photovoltaic cells. These results show the high-quality of these substitute buffer layer materials are prepared through an all-dry technology, which can be used in the manufacture of CIGS thin film solar cells.
基金partially supported by Osawa Scientific Studies Grants Foundation
文摘The flat plane of small surface roughness below 0.1μm average roughness was obtained for monocrystalline diamond by nanosecond pulsed laser irradiation of 1060 nm and post-process acid cleaning,at a laser fluence around the material removal threshold value.The glossy and flat plane at the bottom of the micro-groove was parallel to the top surface of the specimen,although the round beam of Gaussian mode was irradiated in the direction perpendicular to the top surface of specimen.The square beam of top-hat mode produced a shallower micro-groove with a wider,flatter bottom compared with the round beam in Gaussian mode.The creation method of the flat plane with small surface roughness was discussed in the arrangement strategy of linear micro-grooving by the square beam of top-hat mode.Normal side-by-side repetition of linear micro-grooving did not create a flat plane with constant depth.Therefore,a two-step scanning method was proposed in order to overcome the problem in the normal side-by-side repetition of liner micro-grooving.Non-removal areas were partly retained between the processing lines in the first step,and the laser scanning was conducted on the retained area in the second step.The newly proposed two-step scanning method was practical and useful to create a widely flat plane with small surface roughness,and the two-step scanning method provided superior control over the micro-groove depth.This proposed method can reduce the surface roughness in addition to the shape creation of monocrystalline diamond,and it can be used as a high-quality micro-shape fabrication method of monocrystalline diamond.
文摘Functionalized implants demonstrate an upgraded approach in orthopedic implants,aiming to achieve long term success through improved bio integration.Bioceramic coatings with multifunctionality have arisen as an effective substitute for conventional coatings,owing to their combination of various properties that are essential for bio-implants,such as osteointegration and antibacterial character.In the present study,thin hopeite coatings were produced by Pulsed laser deposition(PLD)and radio frequency magnetron sputtering(RFMS)on Ti64 substrates.The obtained hopeite coatings were annealed at 500°C in ambient air and studied in terms of surface morphology,phase composition,surface roughness,adhesion strength,antibacterial efficacy,apatite forming ability,and surface wettability by scanning electron microscope(SEM),X-ray diffraction(XRD),atomic force microscope(AFM),tensometer,fluorescence-activated cell sorting(FACS),simulated body fluid(SBF)immersion test and contact angle goniometer,respectively.Furthermore,based on promising results obtained in the present work it can be summarized that the new generation multifunctional hopeite coating synthesized by two alternative new process routes of PLD and RFMS on Ti64 substrates,provides effective alternatives to conventional coatings,largely attributed to strong osteointegration and antibacterial character of deposited hopeite coating ensuring the overall stability of metallic orthopedic implants.
