The 2024 aluminum alloy is used extensively in the aircraft and aerospace industries because of its excellent mechanical properties.However,the weldability of 2024 aluminum alloy is generally low because it contains a...The 2024 aluminum alloy is used extensively in the aircraft and aerospace industries because of its excellent mechanical properties.However,the weldability of 2024 aluminum alloy is generally low because it contains a high number of solutes,such as copper(Cu),magnesium(Mg),and manganese(Mn),causing solidification cracking.If high speed welding of 2024 aluminum alloy without the use of filler is achieved,the applicability of 2024 aluminum alloys will expand.Grain refining is one of the methods used to prevent solidification cracking in weld metal,although it has never been achieved for high-speed laser welding of 2024 aluminum alloy without filler.Here,we propose a short-pulsed,laser-induced,grain-refining method during continuous wave laser welding without filler.Bead-on-plate welding was performed on a 2024-T3 aluminum alloy at a welding speed of 1 m min−1 with a single mode fiber laser at a wavelength of 1070 nm and power of 1 kW.Areas in and around the molten pool were irradiated with nanosecond laser pulses at a wavelength of 1064 nm,pulse width of 10 ns,and pulse energy of 430 mJ.The grain-refinement effect was confirmed when laser pulses were irradiated on the molten pool.The grain-refinement region was formed in a semicircular shape along the solid–liquid interface.Results of the vertical section indicate that the grain-refinement region reached a depth of 1 mm along the solid–liquid interface.The Vickers hardness test results demonstrated that the hardness increased as a result of grain refinement and that the progress of solidification cracking was suppressed in the grain refinement region.展开更多
The skin effect in the reversely switched dynistor (RSD) devices is investigated in this paper. Based on the plasma bipolar drift model of the RSD, the current density distributions on the chip are simulated with co...The skin effect in the reversely switched dynistor (RSD) devices is investigated in this paper. Based on the plasma bipolar drift model of the RSD, the current density distributions on the chip are simulated with considering the skin effect. The results indicate that the current density on the border can be several hundred to a thousand A/cm2 higher than that in the center of the chip. The skin effect becomes more prominent as the voltage increases and the inductance decreases in the main circuit. The phenomenon that most of a certain group of chips break over on the border has proved the existence of the skin effect.展开更多
The Lie symmetry analysis is performed for the coupled short plus (CSP) equation. We derive the infinitesimals that admit the classical symmetry group. Five types arise depending on the nature of the Lie symmetry ge...The Lie symmetry analysis is performed for the coupled short plus (CSP) equation. We derive the infinitesimals that admit the classical symmetry group. Five types arise depending on the nature of the Lie symmetry generator. In all types, we find reductions in terms of system of ordinary differential equations, and exact solutions of the CSP equation are derived, which are compared with numerical solutions using the classical fourth-order Runge-Kutta scheme.展开更多
Reciprocal transformations of the space-time shifted nonlocal short pulse equations are elaborated.Covariance of dependent and independent variables involved in the reciprocal transformations is investigated.Exact sol...Reciprocal transformations of the space-time shifted nonlocal short pulse equations are elaborated.Covariance of dependent and independent variables involved in the reciprocal transformations is investigated.Exact solutions of the space-time shifted nonlocal short pulse equations are given in terms of double Wronskians.Realness of independent variables involved in the reciprocal transformations is verified.Dynamics of some obtained solutions are illustrated.展开更多
In this paper, dependent and independent variable transformations are introduced to solve the short pulse equation. It is shown that different kinds of solutions can be obtained to the short pulse equation.
The development of a nanosecond discharge in a pin-to-pin gap filled with air at atmospheric pressure has been studied with high temporal and spatial resolutions from a breakdown start to the spark decay.Positive and ...The development of a nanosecond discharge in a pin-to-pin gap filled with air at atmospheric pressure has been studied with high temporal and spatial resolutions from a breakdown start to the spark decay.Positive and negative nanosecond voltage pulses with an amplitude of tens of kilovolts were applied.Time-resolved images of the discharge development were taken with a fourchannel Intensified Charge Coupled Device(ICCD)camera.The minimum delay between the camera channels could be as short as≈0.1 ns.This made it possible to study the gap breakdown process with subnanosecond resolution.It was observed that a wide-diameter streamer develops from the high-voltage pointed electrode.The ionization processes near the grounded pin electrode started when the streamer crossed half of the gap.After bridging the gap by the streamer,a diffuse discharge was formed.The development of spark leaders from bright spots on the surface of the pointed electrodes was observed at the next stage.It was found that the rate of development of the spark leader is an order of magnitude lower than that of the wide-diameter streamer.Long thin luminous tracks were observed against the background of a discharge plasma glow.It has been established that the tracks are adjacent to brightly glowing spots on the electrodes and are associated with the flight of small particles.展开更多
BACKGROUND Alzheimer's disease(AD),characterized by the ongoing deterioration of neural function,often presents alongside depressive features and greatly affects the quality of life of individuals living with the ...BACKGROUND Alzheimer's disease(AD),characterized by the ongoing deterioration of neural function,often presents alongside depressive features and greatly affects the quality of life of individuals living with the condition.Although several treatment methods exist,their efficacy is limited.In recent years,repetitive transcranial magnetic stimulation(rTMS)utilizing the theta burst stimulation(TBS)mode,specifically the intermittent TBS(iTBS),has demonstrated promising therapeutic potential in the management of neuropsychiatric disorders.AIM To examine the therapeutic efficacy of iTBS mode of rTMS for treating depressive symptoms in patients with AD.METHODS This retrospective study enrolled 105 individuals diagnosed with AD with depressive symptoms at Huzhou Third Municipal Hospital,affiliated with Huzhou University,between January 2020 and December 2023.Participants received standard pharmacological interventions and were categorized into control(n=53)and observation(n=52)groups based on treatment protocols.The observation group received iTBS mode of rTMS,while the control group received pseudo-stimulation.A comparative analysis evaluated psychological well-being,adverse events,and therapeutic at initiation of hospitalization(T0)and 15 days post-treatment(T1).RESULTS At T1,both groups exhibited a marked reduction in self-rating depression scale and Hamilton depression scale scores compared to T0.Furthermore,the observa-tion group showed a more pronounced decrease than the control group.By T1,the Mini-mental state examination scores for both groups had increased markedly from their initial T0 assessments.Importantly,the increase was particularly more substantial in the observation group than in the control group.Fourteen patients in the control group had ineffective treatment effects,while five patients in the observation group experienced the same.Additionally,the observation group experienced a substantially reduced incidence of ineffective treatment as compared to the control group(both P<0.05);there were no recorded serious adverse events in either group.CONCLUSION The iTBS model of rTMS effectively treated AD with depression,improving depressive symptoms and cognitive function in patients without serious adverse reactions,warranting clinical consideration.展开更多
This paper investigates experimentally high-order harmonic generation (HHG) of neon gas with 5-fs and 25-fs driving laser pulses. It has been demonstrated that the cutoff energy of the harmonic extreme ultraviolet p...This paper investigates experimentally high-order harmonic generation (HHG) of neon gas with 5-fs and 25-fs driving laser pulses. It has been demonstrated that the cutoff energy of the harmonic extreme ultraviolet photons is extended to 131 eV and the HHC spectrum near the cutoff region becomes continuum as the driving laser pulse duration is 5 fs; whereas much lower cutoff photon energy and discrete harmonic spectrum near the cutoff region are presented as the laser pulse duration is 25 fs. The results can be explained by the fact that neutral atoms can be exposed to more intense laser field before they are depleted by ionization because of the extremely short rising time of the few-cycle pulse. The 5-fs driving laser pulse paves the way of generation of coherent x-ray in the water window and single attosecond pulse.展开更多
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
Based on the documentation of the invited paper and the subsequent discussion at a virtual conference,discoveries are indicated,which are summarized in the following paper for further evaluation on the topic of non-th...Based on the documentation of the invited paper and the subsequent discussion at a virtual conference,discoveries are indicated,which are summarized in the following paper for further evaluation on the topic of non-thermal forces using terms of extremely powerful components of Maxwell’s stress tensor at the interaction of CPA(chirped pulse amplification)laser pulses in the fusion plasmas of hydrogen with the isotope 11 of boron.This is caused by a recoil mechanism given by the Fresnel formulas of the suppression of the reflectivity of inhomogeneous plasma given by optical constants of the plasma properties.展开更多
Experiments of a GaAs ultra\|fast Photo\|Conductive Semiconductor Switch (PCSS) are reported. Both the linear and nonlinear modes were observed when triggered by the μJ nano\|second laser. The peak current could...Experiments of a GaAs ultra\|fast Photo\|Conductive Semiconductor Switch (PCSS) are reported. Both the linear and nonlinear modes were observed when triggered by the μJ nano\|second laser. The peak current could be as high as 560A. The rise time of the current pulse responses is less than 200ps when triggered with 76MHz femto\|second laser.展开更多
The spectral linewidth of a transversely excited pulsed CO_(2) laser is broadened at high working pressures.This phenomenon causes a decrease in the upper-level lifetime such that the pulse width is significantly comp...The spectral linewidth of a transversely excited pulsed CO_(2) laser is broadened at high working pressures.This phenomenon causes a decrease in the upper-level lifetime such that the pulse width is significantly compressed.Although the tail part of CO_(2) laser pulses owns a non-negligible proportion of total energy,it has minor effects during the interaction process between photons and materials due to its low amplitude.Thus,it is of great significance to yield the tail part and generate a narrow pulse in most applications.In this study,a continuously tunable pulsed CO_(2) laser with a low nitrogen proportion in the mixture is developed to generate tail-free short pulses;a minimum pulse width of 30.60 ns with a maximum pulse energy of 481 mJ is synchronously achieved at a pressure of 7 atm,and the estimated peak power is above 15 MW.A numerical simulation is also conducted for comparison with the experimental results.The contribution of the spectral gain toward the compression of the pulse width is discussed in the last section of this paper.展开更多
We report a cavity-dumped 1123 nm laser with narrow pulse width and high peak power by an Mg O: LN crystal electrooptic(EO) modulator. Based on the structural optimization design of a folded biconcave cavity using the...We report a cavity-dumped 1123 nm laser with narrow pulse width and high peak power by an Mg O: LN crystal electrooptic(EO) modulator. Based on the structural optimization design of a folded biconcave cavity using the 808 nm pulsed laser diode(LD) side-pumped ceramic Nd: YAG rod, output pulses with maximum pulse energy and peak power up to39.6 m J and 9.73 MW were obtained, corresponding to 100 Hz repetition rate and 4.07 ns pulse width. The instabilities of pulse width and pulse energy were ±1.55% and ±2.06%, respectively. At the highest repetition rate of 1 kHz, the pulse energy, pulse width, and peak power were 11.3 mJ, 5.05 ns, and 2.24 MW, respectively. The instabilities of pulse width and pulse energy were ±2.65% and ±3.47%, respectively.展开更多
Muons produced by a short pulse laser can serve as a new type of muon source having potential advantages of high intensity, small source emittance, short pulse duration and low cost. To validate it in experiments, a s...Muons produced by a short pulse laser can serve as a new type of muon source having potential advantages of high intensity, small source emittance, short pulse duration and low cost. To validate it in experiments, a suitable muon diagnostics system is needed since high muon flux generated by a short pulse laser shot is always accompanied by high radiation background, which is quite different from cases in general muon researches. A detection system is proposed to distinguish muon signals from radiation background by measuring the muon lifetime. It is based on the scintillator detector with water and lead shields, in which water is used to adjust energies of muons stopped in the scintillator and lead to against radiation background. A Geant 4 simulation on the performance of the detection system shows that efficiency up to 52% could be arrived for low-energy muons around 200 MeV and this efficiency decreases to 14% for high-energy muons above 1000 MeV. The simulation also shows that the muon lifetime can be derived properly by measuring attenuation of the scintilla light of electrons from muon decays inside the scintillator detector.展开更多
The short Hermite-Gaussian optical pulse transmission over 1440 km in a dense dispersion compensated system is investigated based on numerical simulation. In the simulation, compensation is made not only for the group...The short Hermite-Gaussian optical pulse transmission over 1440 km in a dense dispersion compensated system is investigated based on numerical simulation. In the simulation, compensation is made not only for the group-velocity dispersion but also for the third order dispersion. It is demonstrated that the pulse with reasonably lower power can propagate steadily in net zero, positive and negative dispersion system.展开更多
In this paper, the complex short pulse equation and the coupled complex short pulse equations that can describe the ultra-short pulse propagation in optical fibers are investigated. The two complex nonlinear models ar...In this paper, the complex short pulse equation and the coupled complex short pulse equations that can describe the ultra-short pulse propagation in optical fibers are investigated. The two complex nonlinear models are turned into multi-component real models by proper transformations. Lie symmetries are obtained via the classical Lie group method, and the results for the coupled complex short pulse equations contain the existing results as particular cases.Based on the linearizing operator and adjoint linearizing operator for the two real systems,adjoint symmetries can be obtained. Explicit conservation laws are constructed using the symmetry/adjoint symmetry pair(SA) method. Relationships between the nonlinear selfadjointness method and the SA method are investigated.展开更多
A mutual pulse injection-seeding scheme is developed to produce wavelength tunable optical short pulse generation. The sidemode suppression ratio obtained is more than 31 dB over the wavelength-tuning rang of 18 nm.
The self-assembled growth of InAs/GaAs quantum dots by molecular beam epitaxy is conducted by optimizing several growth parameters, using a one-step interruption method after island formation. The dependence of photol...The self-assembled growth of InAs/GaAs quantum dots by molecular beam epitaxy is conducted by optimizing several growth parameters, using a one-step interruption method after island formation. The dependence of photoluminescence on areal quantum-dot density is systematically investigated as a function of InAs deposition, growth temperature and arsenic pressure. The results of this investigation along with time-resolved photoluminescence measurements show that the com- bination of a growth temperature of 490℃, with a deposition rate of 0.02 ML/s, under an arsenic pressure of 1×10^-6 Torr (1 Torr = 1.33322×10^2 Pa), provides the best compromise between high density and the photoluminescence of quantum dot structure, with a radiative lifetime of 780 ps. The applicability of this 5-layer quantum dot structure to high-repetition-rate pulsed lasers is demonstrated with the fabrication and characterization of a monolithic InAs/GaAs quantum-dot passively mode-locked laser operating at nearly 1300 nm. Picosecond pulse generation is achieved from a two-section laser, with a 19.7-GHz repetition rate.展开更多
We present an interferometry setup and the detailed fringe analysis method for intense short pulse(SP) laser experiments.The interferometry scheme was refined through multiple campaigns to investigate the effects of p...We present an interferometry setup and the detailed fringe analysis method for intense short pulse(SP) laser experiments.The interferometry scheme was refined through multiple campaigns to investigate the effects of pre-plasmas on energetic electrons at the Jupiter Laser Facility at Lawrence Livermore National Laboratory. The interferometer used a frequency doubled(λ=0.527 μm) 0.5 ps long optical probe beam to measure the pre-plasma density, an invaluable parameter to better understand how varying pre-plasma conditions affect the characteristics of the energetic electrons. The hardware of the diagnostic, data analysis and example data are presented. The diagnostic setup and the analysis procedure can be employed for any other SP laser experiments and interferograms, respectively.展开更多
The resonant third-harmonic generation of a tion was investigated. Because of self-focusing self-focusing laser in plasma with a density transi- of the fundamental laser pulse, a transverse intensity gradient was crea...The resonant third-harmonic generation of a tion was investigated. Because of self-focusing self-focusing laser in plasma with a density transi- of the fundamental laser pulse, a transverse intensity gradient was created, which generated a plasma wave at the fundamental wave frequency. Phase matching was satisfied by using a Wiggler magnetic field, which provided additional angular too- mentum to the third-harmonic photon to make the process resonant. An enhancement was observed in the resonant third-harmonic generation of an intense short-pulse laser in plasma embedded with a magnetic Wiggler with a density transition. A plasma density ramp played an important role in the self-focusing, enhancing the third-harmonic generation in plasma. We also examined the ef- fect of the Wiggler magnetic field on the pulse slippage of the third-harmonic pulse in plasma. The pulse slippage was due to the group-velocity mismatch between the fundamental and third-harmonic pulses.展开更多
基金The authors would like to thank Mr Tetsuji Kuwabara of NAC Image Technology Inc.for support of high-speed photographingThis work was supported in part by MEXT Quantum Leap Flagship Program(MEXT Q-LEAP)Grant No.JPMXS0118068348,JSPS KAKENHI Grant Nos.JP16H04247,JP16K14417,and 19K22061This work was funded in part by ImPACT Program of Council for Science,Technology and Innovation(Cabinet Office,Government of Japan).
文摘The 2024 aluminum alloy is used extensively in the aircraft and aerospace industries because of its excellent mechanical properties.However,the weldability of 2024 aluminum alloy is generally low because it contains a high number of solutes,such as copper(Cu),magnesium(Mg),and manganese(Mn),causing solidification cracking.If high speed welding of 2024 aluminum alloy without the use of filler is achieved,the applicability of 2024 aluminum alloys will expand.Grain refining is one of the methods used to prevent solidification cracking in weld metal,although it has never been achieved for high-speed laser welding of 2024 aluminum alloy without filler.Here,we propose a short-pulsed,laser-induced,grain-refining method during continuous wave laser welding without filler.Bead-on-plate welding was performed on a 2024-T3 aluminum alloy at a welding speed of 1 m min−1 with a single mode fiber laser at a wavelength of 1070 nm and power of 1 kW.Areas in and around the molten pool were irradiated with nanosecond laser pulses at a wavelength of 1064 nm,pulse width of 10 ns,and pulse energy of 430 mJ.The grain-refinement effect was confirmed when laser pulses were irradiated on the molten pool.The grain-refinement region was formed in a semicircular shape along the solid–liquid interface.Results of the vertical section indicate that the grain-refinement region reached a depth of 1 mm along the solid–liquid interface.The Vickers hardness test results demonstrated that the hardness increased as a result of grain refinement and that the progress of solidification cracking was suppressed in the grain refinement region.
基金supported by the National Natural Science Foundation of China under Grant No.50577028the Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant No.20050487044the China Postdoctoral Science Foundation under Grant No.20080440931
文摘The skin effect in the reversely switched dynistor (RSD) devices is investigated in this paper. Based on the plasma bipolar drift model of the RSD, the current density distributions on the chip are simulated with considering the skin effect. The results indicate that the current density on the border can be several hundred to a thousand A/cm2 higher than that in the center of the chip. The skin effect becomes more prominent as the voltage increases and the inductance decreases in the main circuit. The phenomenon that most of a certain group of chips break over on the border has proved the existence of the skin effect.
文摘The Lie symmetry analysis is performed for the coupled short plus (CSP) equation. We derive the infinitesimals that admit the classical symmetry group. Five types arise depending on the nature of the Lie symmetry generator. In all types, we find reductions in terms of system of ordinary differential equations, and exact solutions of the CSP equation are derived, which are compared with numerical solutions using the classical fourth-order Runge-Kutta scheme.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11875040 and 12171308)
文摘Reciprocal transformations of the space-time shifted nonlocal short pulse equations are elaborated.Covariance of dependent and independent variables involved in the reciprocal transformations is investigated.Exact solutions of the space-time shifted nonlocal short pulse equations are given in terms of double Wronskians.Realness of independent variables involved in the reciprocal transformations is verified.Dynamics of some obtained solutions are illustrated.
基金supported by National Natural Science Foundation of China under Grant Nos.40775040 and 90511009
文摘In this paper, dependent and independent variable transformations are introduced to solve the short pulse equation. It is shown that different kinds of solutions can be obtained to the short pulse equation.
基金performed within the framework of the State assignment of the IHCE SB RAS,project No.FWRM-2021-0014.
文摘The development of a nanosecond discharge in a pin-to-pin gap filled with air at atmospheric pressure has been studied with high temporal and spatial resolutions from a breakdown start to the spark decay.Positive and negative nanosecond voltage pulses with an amplitude of tens of kilovolts were applied.Time-resolved images of the discharge development were taken with a fourchannel Intensified Charge Coupled Device(ICCD)camera.The minimum delay between the camera channels could be as short as≈0.1 ns.This made it possible to study the gap breakdown process with subnanosecond resolution.It was observed that a wide-diameter streamer develops from the high-voltage pointed electrode.The ionization processes near the grounded pin electrode started when the streamer crossed half of the gap.After bridging the gap by the streamer,a diffuse discharge was formed.The development of spark leaders from bright spots on the surface of the pointed electrodes was observed at the next stage.It was found that the rate of development of the spark leader is an order of magnitude lower than that of the wide-diameter streamer.Long thin luminous tracks were observed against the background of a discharge plasma glow.It has been established that the tracks are adjacent to brightly glowing spots on the electrodes and are associated with the flight of small particles.
基金Huzhou Science and Technology Plan Project,No.2019GZ38.
文摘BACKGROUND Alzheimer's disease(AD),characterized by the ongoing deterioration of neural function,often presents alongside depressive features and greatly affects the quality of life of individuals living with the condition.Although several treatment methods exist,their efficacy is limited.In recent years,repetitive transcranial magnetic stimulation(rTMS)utilizing the theta burst stimulation(TBS)mode,specifically the intermittent TBS(iTBS),has demonstrated promising therapeutic potential in the management of neuropsychiatric disorders.AIM To examine the therapeutic efficacy of iTBS mode of rTMS for treating depressive symptoms in patients with AD.METHODS This retrospective study enrolled 105 individuals diagnosed with AD with depressive symptoms at Huzhou Third Municipal Hospital,affiliated with Huzhou University,between January 2020 and December 2023.Participants received standard pharmacological interventions and were categorized into control(n=53)and observation(n=52)groups based on treatment protocols.The observation group received iTBS mode of rTMS,while the control group received pseudo-stimulation.A comparative analysis evaluated psychological well-being,adverse events,and therapeutic at initiation of hospitalization(T0)and 15 days post-treatment(T1).RESULTS At T1,both groups exhibited a marked reduction in self-rating depression scale and Hamilton depression scale scores compared to T0.Furthermore,the observa-tion group showed a more pronounced decrease than the control group.By T1,the Mini-mental state examination scores for both groups had increased markedly from their initial T0 assessments.Importantly,the increase was particularly more substantial in the observation group than in the control group.Fourteen patients in the control group had ineffective treatment effects,while five patients in the observation group experienced the same.Additionally,the observation group experienced a substantially reduced incidence of ineffective treatment as compared to the control group(both P<0.05);there were no recorded serious adverse events in either group.CONCLUSION The iTBS model of rTMS effectively treated AD with depression,improving depressive symptoms and cognitive function in patients without serious adverse reactions,warranting clinical consideration.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 60608003,10874237 and 60808007)the National Basic Research Program of China (973 Program) (Grant No. 2007CB815104)
文摘This paper investigates experimentally high-order harmonic generation (HHG) of neon gas with 5-fs and 25-fs driving laser pulses. It has been demonstrated that the cutoff energy of the harmonic extreme ultraviolet photons is extended to 131 eV and the HHC spectrum near the cutoff region becomes continuum as the driving laser pulse duration is 5 fs; whereas much lower cutoff photon energy and discrete harmonic spectrum near the cutoff region are presented as the laser pulse duration is 25 fs. The results can be explained by the fact that neutral atoms can be exposed to more intense laser field before they are depleted by ionization because of the extremely short rising time of the few-cycle pulse. The 5-fs driving laser pulse paves the way of generation of coherent x-ray in the water window and single attosecond pulse.
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Based on the documentation of the invited paper and the subsequent discussion at a virtual conference,discoveries are indicated,which are summarized in the following paper for further evaluation on the topic of non-thermal forces using terms of extremely powerful components of Maxwell’s stress tensor at the interaction of CPA(chirped pulse amplification)laser pulses in the fusion plasmas of hydrogen with the isotope 11 of boron.This is caused by a recoil mechanism given by the Fresnel formulas of the suppression of the reflectivity of inhomogeneous plasma given by optical constants of the plasma properties.
文摘Experiments of a GaAs ultra\|fast Photo\|Conductive Semiconductor Switch (PCSS) are reported. Both the linear and nonlinear modes were observed when triggered by the μJ nano\|second laser. The peak current could be as high as 560A. The rise time of the current pulse responses is less than 200ps when triggered with 76MHz femto\|second laser.
基金This work was supported by the open fund of Science and Technology on Particle Transport and Separation Laboratory(No.QT210005).
文摘The spectral linewidth of a transversely excited pulsed CO_(2) laser is broadened at high working pressures.This phenomenon causes a decrease in the upper-level lifetime such that the pulse width is significantly compressed.Although the tail part of CO_(2) laser pulses owns a non-negligible proportion of total energy,it has minor effects during the interaction process between photons and materials due to its low amplitude.Thus,it is of great significance to yield the tail part and generate a narrow pulse in most applications.In this study,a continuously tunable pulsed CO_(2) laser with a low nitrogen proportion in the mixture is developed to generate tail-free short pulses;a minimum pulse width of 30.60 ns with a maximum pulse energy of 481 mJ is synchronously achieved at a pressure of 7 atm,and the estimated peak power is above 15 MW.A numerical simulation is also conducted for comparison with the experimental results.The contribution of the spectral gain toward the compression of the pulse width is discussed in the last section of this paper.
基金supported by the National Natural Science Foundation of China (No. 61205114)the Key Laboratory Project – scientific research plan of Shaanxi Provincial Department of Education (No. 2010JS112)
文摘We report a cavity-dumped 1123 nm laser with narrow pulse width and high peak power by an Mg O: LN crystal electrooptic(EO) modulator. Based on the structural optimization design of a folded biconcave cavity using the 808 nm pulsed laser diode(LD) side-pumped ceramic Nd: YAG rod, output pulses with maximum pulse energy and peak power up to39.6 m J and 9.73 MW were obtained, corresponding to 100 Hz repetition rate and 4.07 ns pulse width. The instabilities of pulse width and pulse energy were ±1.55% and ±2.06%, respectively. At the highest repetition rate of 1 kHz, the pulse energy, pulse width, and peak power were 11.3 mJ, 5.05 ns, and 2.24 MW, respectively. The instabilities of pulse width and pulse energy were ±2.65% and ±3.47%, respectively.
基金supported by the Science Challenge Project (No.JCKY2016212A505)the CAEP Foundation (No.2014A0102003)
文摘Muons produced by a short pulse laser can serve as a new type of muon source having potential advantages of high intensity, small source emittance, short pulse duration and low cost. To validate it in experiments, a suitable muon diagnostics system is needed since high muon flux generated by a short pulse laser shot is always accompanied by high radiation background, which is quite different from cases in general muon researches. A detection system is proposed to distinguish muon signals from radiation background by measuring the muon lifetime. It is based on the scintillator detector with water and lead shields, in which water is used to adjust energies of muons stopped in the scintillator and lead to against radiation background. A Geant 4 simulation on the performance of the detection system shows that efficiency up to 52% could be arrived for low-energy muons around 200 MeV and this efficiency decreases to 14% for high-energy muons above 1000 MeV. The simulation also shows that the muon lifetime can be derived properly by measuring attenuation of the scintilla light of electrons from muon decays inside the scintillator detector.
基金This research is supported by the National Natural Science Foundation of China (No. 10074041) and the Shanxi Province Youth Science Foundation (No. 20011015). Y. Xiao's e-mail address is xiaoyan @ mail. sxu. edu. cn.
文摘The short Hermite-Gaussian optical pulse transmission over 1440 km in a dense dispersion compensated system is investigated based on numerical simulation. In the simulation, compensation is made not only for the group-velocity dispersion but also for the third order dispersion. It is demonstrated that the pulse with reasonably lower power can propagate steadily in net zero, positive and negative dispersion system.
基金funded by the National Natural Science Foundation of China(No.12105073)Science and Technology Program of Colleges and Universities in Hebei Province(No.QN2020144)+2 种基金Science and Technology Plan Project(Special Program for Soft Science)in Hebei Province(No.20556201D)Scientific Research and Development Program Fund Project of Hebei University of Economics and Business(Nos.2020YB15,2020YB12 and 2021ZD07)Youth Team Support Program of Hebei University of Economics and Business。
文摘In this paper, the complex short pulse equation and the coupled complex short pulse equations that can describe the ultra-short pulse propagation in optical fibers are investigated. The two complex nonlinear models are turned into multi-component real models by proper transformations. Lie symmetries are obtained via the classical Lie group method, and the results for the coupled complex short pulse equations contain the existing results as particular cases.Based on the linearizing operator and adjoint linearizing operator for the two real systems,adjoint symmetries can be obtained. Explicit conservation laws are constructed using the symmetry/adjoint symmetry pair(SA) method. Relationships between the nonlinear selfadjointness method and the SA method are investigated.
文摘A mutual pulse injection-seeding scheme is developed to produce wavelength tunable optical short pulse generation. The sidemode suppression ratio obtained is more than 31 dB over the wavelength-tuning rang of 18 nm.
基金Project supported by the Natural Science Foundation of Beijing,China (Grant No.4112060)the Special Foundation for National Key Scientific Instrument,China (Grant No.2012YQ140005)+5 种基金the Open Fund of High Power Laser Laboratory,China Academy of Engineering Physics (Grant No.2013HEL03)the National Natural Science Foundation of China (Grant No.61274125)the National Basic Research Program,China (Grant No.2010CB327601)the State Key Laboratory on Integrated Optoelectronics Open Project,China (Grant No.2011KFB002)financially supported by a Marie Curie International Incoming Fellowship within the 7th European Community Framework Programmethe financial support through a Royal Academy of Engineering/EPSRC Research Fellowship
文摘The self-assembled growth of InAs/GaAs quantum dots by molecular beam epitaxy is conducted by optimizing several growth parameters, using a one-step interruption method after island formation. The dependence of photoluminescence on areal quantum-dot density is systematically investigated as a function of InAs deposition, growth temperature and arsenic pressure. The results of this investigation along with time-resolved photoluminescence measurements show that the com- bination of a growth temperature of 490℃, with a deposition rate of 0.02 ML/s, under an arsenic pressure of 1×10^-6 Torr (1 Torr = 1.33322×10^2 Pa), provides the best compromise between high density and the photoluminescence of quantum dot structure, with a radiative lifetime of 780 ps. The applicability of this 5-layer quantum dot structure to high-repetition-rate pulsed lasers is demonstrated with the fabrication and characterization of a monolithic InAs/GaAs quantum-dot passively mode-locked laser operating at nearly 1300 nm. Picosecond pulse generation is achieved from a two-section laser, with a 19.7-GHz repetition rate.
基金support from the LDRD (15-ERD-054) program to finish the manuscriptthe auspices of the US DOE by LLNL under contract no.DEAC52-07NA27344funded by the LDRD (12-ERD-062) program
文摘We present an interferometry setup and the detailed fringe analysis method for intense short pulse(SP) laser experiments.The interferometry scheme was refined through multiple campaigns to investigate the effects of pre-plasmas on energetic electrons at the Jupiter Laser Facility at Lawrence Livermore National Laboratory. The interferometer used a frequency doubled(λ=0.527 μm) 0.5 ps long optical probe beam to measure the pre-plasma density, an invaluable parameter to better understand how varying pre-plasma conditions affect the characteristics of the energetic electrons. The hardware of the diagnostic, data analysis and example data are presented. The diagnostic setup and the analysis procedure can be employed for any other SP laser experiments and interferograms, respectively.
文摘The resonant third-harmonic generation of a tion was investigated. Because of self-focusing self-focusing laser in plasma with a density transi- of the fundamental laser pulse, a transverse intensity gradient was created, which generated a plasma wave at the fundamental wave frequency. Phase matching was satisfied by using a Wiggler magnetic field, which provided additional angular too- mentum to the third-harmonic photon to make the process resonant. An enhancement was observed in the resonant third-harmonic generation of an intense short-pulse laser in plasma embedded with a magnetic Wiggler with a density transition. A plasma density ramp played an important role in the self-focusing, enhancing the third-harmonic generation in plasma. We also examined the ef- fect of the Wiggler magnetic field on the pulse slippage of the third-harmonic pulse in plasma. The pulse slippage was due to the group-velocity mismatch between the fundamental and third-harmonic pulses.