High-power laser technology is widely used in manufacturing processing,medical diagnosis,and treatment,and is one of the important fields of strategic high-tech competition in China at the moment.In the context of ind...High-power laser technology is widely used in manufacturing processing,medical diagnosis,and treatment,and is one of the important fields of strategic high-tech competition in China at the moment.In the context of industrial upgrading,high-power laser technology plays an important role in leading the development of the manufacturing industry and industrial intelligence.Based on this,this paper carries out research on high-power laser technology and industry,summarizes the basic principle and classification of high-power laser technology,analyzes the current status of high-power laser technology industry,points out the opportunities and challenges faced by the industry development,puts forward suggestions to promote the development of high-power laser technology industry,and to provide an effective reference for the application and development of high-power laser technology.展开更多
We propose a novel scheme for the population and depletion of nuclear isomers.This scheme combines the γ photons with energiesà 10 keV emitted during the interaction of a contemporary high-intensity laser pulse ...We propose a novel scheme for the population and depletion of nuclear isomers.This scheme combines the γ photons with energiesà 10 keV emitted during the interaction of a contemporary high-intensity laser pulse with a plasma and one or multiple photon beams supplied by intense lasers.Owing to nonlinear effects,two-or multiphoton absorption dominates over the conventional multistep one-photon process for an optimized γ flash.Moreover,this nonlinear effect can be greatly enhanced with the help of externally supplied low-energy photons coming from another laser.These low-energy photons act such that the effective cross-section experienced by the γ photons becomes tunable,growing with the intensity I_(0) of the beam.Assuming I_(0)~10^(18) W·cm^(-2) for the photon beam,an effective cross-section as large as 10^(-21)-10^(-28) cm^(2) for the γ photons can be achieved.Thus,with state-of-the-art 10 PW laser facilities,the yields from two-photon absorption can reach 10^(6)-10^(9) isomers per shot for selected states that are separated from their ground state by E2 transitions.Similar yields for transitions with higher multipolarities can be accommodated by multiphoton absorption with additional photons provided.展开更多
Due to laser-induced damage, the aperture of optics is one of the main factors limiting the output capability of highpower laser facilities. Because of the general difficulty in achieving large-aperture optics, an alt...Due to laser-induced damage, the aperture of optics is one of the main factors limiting the output capability of highpower laser facilities. Because of the general difficulty in achieving large-aperture optics, an alternative solution is to tile some small-aperture ones together. We propose an accurate, stable, and automatic method of array element tiling and verify it on a double-pass 1 × 2 tiled-grating compressor in the XG-III laser facility. The test results show the accuracy and stability of the method. This research provides an efficient way to obtain large-aperture optics for high-power laser facilities.展开更多
Intensive electromagnetic pulses （EMPs） can be generated when a high-power laser strikes a target. The transient electromagnetic field can have an intensity of up to several hundred kV m- 1 with a broad frequency of...Intensive electromagnetic pulses （EMPs） can be generated when a high-power laser strikes a target. The transient electromagnetic field can have an intensity of up to several hundred kV m- 1 with a broad frequency of up to several gigahertz, which may affect diagnostics and interfere with, or even damage, electronic equipment. In this paper, the process in which hot electrons produced by the laser-target interaction radiate EMPs is studied and simulated. The physical process is divided into three stages which are： the production of hot electrons; the escape of hot electrons; and the generation of EMPs. Instead of using a general finite difference time domain （FDTD） method to solve the Maxwell equations, a particle-in-cell method together with a time- biased FDTD method is applied in EMP simulation to restrain high-frequency noise. The results show that EMPs are stronger with higher laser intensity and larger target size.展开更多
High-power laser induced thermal blooming effects in a closed chamber with three different gases are investigated theoretically and experimentally in this work. In the theoretical treatment, an incompressible gas turb...High-power laser induced thermal blooming effects in a closed chamber with three different gases are investigated theoretically and experimentally in this work. In the theoretical treatment, an incompressible gas turbulent model is adopted.In the numerical simulation the gas refractive index as a function of both the temperature and pressure is taken into consideration. In the experimental study the pump-probe technology is adopted. A high-power 1064-nm fiber laser with maximum output power of 12 k W is used to drive the gas thermal blooming, and a 50-m W high-beam-quality 637-nm laser diode(LD)is used as a probe beam. The influences of the gas thermal blooming in the chamber on the probe beam wavefront and beam quality are analyzed for three different gases of air, nitrogen, and helium, respectively. The results indicate that nitrogen is well suitable for restraining thermal blooming effect for high-power laser. The measured data are in good agreement with the simulated results.展开更多
A compact, efficient and high-power laser diode （LD） single-end-pumped Nd：YVO4 laser with continuous-wave emission at 1342 nm is reported. With a single crystal single-end-pumped by fibre-coupled LD array, an outpu...A compact, efficient and high-power laser diode （LD） single-end-pumped Nd：YVO4 laser with continuous-wave emission at 1342 nm is reported. With a single crystal single-end-pumped by fibre-coupled LD array, an output power of 7.36W is obtained from the laser cavity of concave-convex shape, corresponding to an optical-to-optical efficiency of 32.8%. The laser is operated in TEM00 mode with small rms amplitude noise of 0.3%. The influences of the Nd concentration, transmissivity of the output mirror and the cavity length on the output power have been studied experimentally.展开更多
Dear Editor,I am Dr.Shan-Shan Li,from Northern Jiangsu People’s Hospital,Yangzhou,China.I write to present the case of formation of choroidal neovascularization(CNV)under the fovea after high-power laser irradiation....Dear Editor,I am Dr.Shan-Shan Li,from Northern Jiangsu People’s Hospital,Yangzhou,China.I write to present the case of formation of choroidal neovascularization(CNV)under the fovea after high-power laser irradiation.Currently,there is an increasing availability and accessibility to laser instruments,but improper use of these tools can lead to macular damage and irreversible visual impairment.展开更多
Lutetium aluminum garnet doped with cerium(LuAG:Ce)thin films have been identified as a promising material for high-power laser-driven lighting applications.In this study,spray pyrolysis we employed to fabricate LuAG:...Lutetium aluminum garnet doped with cerium(LuAG:Ce)thin films have been identified as a promising material for high-power laser-driven lighting applications.In this study,spray pyrolysis we employed to fabricate LuAG:Ce films on sapphire substrates and the impact of film thickness on thermal management and light emission efficiency was investigated.Our results show that,regardless of thickness,LuAGiCe films exhibit impressive internal quantum efficiencies(IQE)exceeding 83.2%and external quantum efficiencies(EQE)surpassing 56.4%,with minimal alteration of luminescent color.Notably,thinner films facilitate more efficient heat dissipation to the underlying sapphire substrate,resulting in superior thermal management and outstanding luminous performance under high-power laser excitation.Specifically,the thinnest LuAG:Ce film(15.79μm)exhibited rapid thermal stabilization(~130℃ within 30s)and maintained stability during continuous irradiation lasting 30 min,with a corresponding decrease in luminous flux to 87.9%of its initial value within the first 60 s.This film also demonstrated relatively high and stable conversion efficiency and luminous efficiency,achieving higher saturation thresholds(15 W·mm^(-2))and luminous flux(1070 lm).In contrast,thicker films exhibited a shift in the saturation point toward lower power densities.These findings provide valuable insights for the practical implementation of LuAG:Ce films in advanced lighting technologies.展开更多
From sevenal models about damage mechanism, the damage mechanism of optical films and the factors which affect the damage threshold are described experimentally and theoretically. Some reasonable proposals are given i...From sevenal models about damage mechanism, the damage mechanism of optical films and the factors which affect the damage threshold are described experimentally and theoretically. Some reasonable proposals are given in this paper on how to select the high-threshold films.展开更多
Inertial confinement fusion(ICF)requires a constant search for the most effective materials to improve the efficiency of compression of the capsule and of laser-to-target energy transfer.Foams could provide a solution...Inertial confinement fusion(ICF)requires a constant search for the most effective materials to improve the efficiency of compression of the capsule and of laser-to-target energy transfer.Foams could provide a solution,but they require further experimental and theoretical investigation.The new 3D-printing technologies,such as two-photon polymerization,are opening a new era in the production of foams,allowing fine control of material morphology.Very few detailed studies of the interaction of foams with high-power lasers in regimes relevant for ICF have been described in the literature to date,and more investigation is needed.In this work,we present the results of an experimental campaign performed at the ABC laser facility at ENEA Centro Ricerche Frascati in which 3D-printed microstructured materials were irradiated at high power.3D simulations of the laser-target interaction performed with the FLASH code reveal that the laser is scattered by plasma density gradients and channeled into the structure when the center of the focal spot is on the through hole.The time required for the laser to completely ablate the structure given by the simulations is in good agreement with the experimental measurement.Measurements of the reflected and transmitted laser light indicate that scattering occurred during the irradiation,in accordance with the simulations.Two-plasmon decay has also been found to be active during irradiation.展开更多
Accurate characterization of high-power laser parameters,especially the near-field and far-field distributions,is crucial for inertial confinement fusion experiments.In this paper,we propose a method for computational...Accurate characterization of high-power laser parameters,especially the near-field and far-field distributions,is crucial for inertial confinement fusion experiments.In this paper,we propose a method for computationally reconstructing the complex amplitude of high-power laser beams using modified coherent modulation imaging.This method has the advantage of being able to simultaneously calculate both the near-field(intensity and wavefront/phase)and far-field(focal-spot)distributions using the reconstructed complex amplitude.More importantly,the focal-spot distributions at different focal planes can also be calculated.To verify the feasibility,the complex amplitude optical field of the highpower pulsed laser was measured after static aberrations calibration.Experimental results also indicate that the near-field wavefront resolution of this method is higher than that of the Hartmann measurement.In addition,the far-field focal spot exhibits a higher dynamic range(176 dB)than that of traditional direct imaging(62 dB).展开更多
Accelerator-driven systems(ADSs)may offer a promising technology for energy production and transmutation of nuclear waste.Here we introduce the concept of utilizing high-intensity laser acceleration technology in real...Accelerator-driven systems(ADSs)may offer a promising technology for energy production and transmutation of nuclear waste.Here we introduce the concept of utilizing high-intensity laser acceleration technology in realizing an ADS,with a focus on the use of thorium fuel in subcritical systems.We explore state-of-the-art laser-driven particle sources for neutron generation by nuclear fusion,spallation or photonuclear reactions and the prospect of reaching the flux of 10^(15)n/s required to drive a subcritical reactor.We review recent advances in high-power laser amplification and assess their technological readiness in view of integration in an ADS.Finally,we present a risk analysis of a laser-driven ADS in terms of laser and target development,radiation safety and operational stability.Our conclusion highlights the potential of laser-driven ADSs as a transformative approach to nuclear fission energy.With continued research and development,technological hurdles can be overcome to fully realize sustainable,green energy production that can meet global energy demands while addressing safety and environmental concerns.展开更多
Cladding light strippers(CLSs)are essential components for high-power monolithic fiber laser systems.Because they allow for bending of the fiber,which leads to an excellent stripping efficiency of light with a low ray...Cladding light strippers(CLSs)are essential components for high-power monolithic fiber laser systems.Because they allow for bending of the fiber,which leads to an excellent stripping efficiency of light with a low ray angle,refractive index-based CLSs have an advantage over the commonly used alternative approaches.However,conventional high-index CLSs overheat at relatively low input power as the maximum temperature,located in a hot-spot,increases linearly with the input power.This applies particularly to CLSs in thulium-based fiber systems,where very low power can already lead to extreme heat generation due to the high cladding material absorption around 2μm.Here,we investigate materials with a highly negative thermooptical coefficient combined with a refractive index closely above glass to distribute the stripped power and heat uniformly along an increased fiber length.Analyzing multiple CLS geometries for fiber diameters of 125 and 400μm,we show record-high maximum input powers for single-material CLSs of 21.8 W for the signal(2039 nm)and 675 W for the pump wavelength(793 nm).Transmitting excess light instead of overheating,this wavelength-adaptable self-protecting CLS concept is fast to apply onsite in the lab and reaches stripping efficiencies of>40 dB in the bent version.展开更多
The authors report the development of aλ~4.1μm quantum cascade laser grown by metal-organic chemical vapor deposition using strain-balanced In Ga As/In Al As materials.A device with a 7.5 mm cavity length and 6.5μm...The authors report the development of aλ~4.1μm quantum cascade laser grown by metal-organic chemical vapor deposition using strain-balanced In Ga As/In Al As materials.A device with a 7.5 mm cavity length and 6.5μm ridge width,bonded to an aluminum nitride heatsink,achieves maximum output powers of 3.4 W at 288 K in pulsed mode and 1.6 W at288 K in continuous-wave(CW)operation,with corresponding maximum wall-plug efficiencies of 14.8%and 9.3%.A kink is observed in the power–current curve under CW operation,which is absent in pulsed operation.Near-field results show that in CW operation,the horizontal beam quality factor M2fluctuates with current,indicating mode instability and highorder lateral mode excitation,while in pulsed mode,the horizontal M2remains stable around 1.3 as the current increases from 1.4 A to 1.9 A.展开更多
A large laser spark was produced in a homogeneous sulphur hexafluoride gas(pressures ranged from 10.7 to 101.3 kPa)by a focused high-power laser pulse(350 ps,125 J,1315.2 nm).Magnetic fields,electromagnetic pulses(EMP...A large laser spark was produced in a homogeneous sulphur hexafluoride gas(pressures ranged from 10.7 to 101.3 kPa)by a focused high-power laser pulse(350 ps,125 J,1315.2 nm).Magnetic fields,electromagnetic pulses(EMPs),optical emission spectra(OES)and chemical changes associated with the laser-induced dielectric breakdown(LIDB)in the SF6 gas were investigated.During the laser interaction,hot electrons escaping the plasma kernel produced EMPs and spontaneous magnetic fields,the frequency spectrum of which contains three bands around 1.15,2.1 and 3 GHz,while the EMP frequency band appeared around 1.1 GHz.The EMP emission from a laser spark was very weak in comparison to those generated at a solid target.Gas chromatography revealed the formation of only a limited number of products and a low degree of sulphur hexafluoride(SF_(6))conversion.OES diagnosed the LIDB plasma in the phase of its formation as well as during its recombination.展开更多
High-power lasers are vital for particle acceleration,imaging,fusion and materials processing,requiring precise control and high-energy delivery.Laser plasma accelerators(LPAs)demand laser positional stability at focu...High-power lasers are vital for particle acceleration,imaging,fusion and materials processing,requiring precise control and high-energy delivery.Laser plasma accelerators(LPAs)demand laser positional stability at focus to ensure consistent electron beams in applications such as X-ray free-electron lasers and high-energy colliders.Achieving this stability is especially challenging for the low-repetition-rate lasers in current LPAs.We present a machine learning method that predicts and corrects laser pointing instabilities in real-time using a high-frequency pilot beam.By preemptively adjusting a correction mirror,this approach overcomes traditional feedback limits.Demonstrated on the BELLA petawatt laser operating at the terawatt level(30 mJ amplification),our method achieved root mean square pointing stabilization of 0.34 and 0.59μrad in the x and y directions,reducing jitter by 65%and 47%,respectively.This is the first successful application of predictive control for shot-to-shot stabilization in low-repetition-rate laser systems,paving the way for full-energy petawatt lasers and transformative advances across science,industry and security.展开更多
Ultra-broadband supercontinuum(SC)lasers covering the mid-infrared(MIR)region have significant applications in trace substance detection,national defense,and biomedical fields.Currently,high-power SC spanning2–5μm i...Ultra-broadband supercontinuum(SC)lasers covering the mid-infrared(MIR)region have significant applications in trace substance detection,national defense,and biomedical fields.Currently,high-power SC spanning2–5μm is still dominated by traditional fluoride(InF_(3))fibers.Although tellurite fibers,with their excellent chemical and thermal stability,have demonstrated significantly higher power scalability compared to other MIR fibers,their spectral broadening capabilities in the 4–5μm region remain largely unexplored.Here,we demonstrate a>10 W ultra-broadband flat SC spanning the 1.8–5.1μm spectral range in a fluorotellurite fiber using a cascaded soliton self-frequency shifting technique.The fluorotellurite fiber is precisely tapered to reconstruct dispersion and nonlinearity,which facilitates the evolution of the pre-stage Raman soliton into higherorder solitons,thereby enabling a new round of“rapid relay fission.”At a low pump power of 7.5 W,we also achieved a high-power(0.5 W)Raman soliton(60 fs)at 4.3μm.These results,for the first time,to our knowledge,demonstrate that tapered fluorotellurite fibers can be used for high-power femtosecond pulse generation beyond4μm and high-power SC generation beyond 5μm,establishing them as an exceptional nonlinear medium for the development of high-power MIR fiber lasers in the 4–5μm spectral region.展开更多
Classification of plume and spatter images was studied to evaluate the welding stability. A high-speed camera was used to capture the instantaneous images of plume and spatters during high power disk laser welding. Ch...Classification of plume and spatter images was studied to evaluate the welding stability. A high-speed camera was used to capture the instantaneous images of plume and spatters during high power disk laser welding. Characteristic parameters such as the area and number of spatters, the average grayscale of a spatter image, the entropy of a spatter grayscale image, the coordinate ratio of the plume centroid and the welding point, the polar coordinates of the plume centroid were defined and extracted. Karhunen-Loeve transform method was used to change the seven characteristics into three primary characteristics to reduce the dimensions. Also, K-nearest neighbor method was used to classify the plume and spatter images into two categories such as good and poor welding quality. The results show that plume and spatter have a close relationship with the welding stability, and two categories could be recognized effectively using K-nearest neighbor method based on Karhunen-Loeve transform.展开更多
Giant electromagnetic pulses(EMP) generated during the interaction of high-power lasers with solid targets can seriously degrade electrical measurements and equipment. EMP emission is caused by the acceleration of hot...Giant electromagnetic pulses(EMP) generated during the interaction of high-power lasers with solid targets can seriously degrade electrical measurements and equipment. EMP emission is caused by the acceleration of hot electrons inside the target, which produce radiation across a wide band from DC to terahertz frequencies. Improved understanding and control of EMP is vital as we enter a new era of high repetition rate, high intensity lasers(e.g. the Extreme Light Infrastructure).We present recent data from the VULCAN laser facility that demonstrates how EMP can be readily and effectively reduced. Characterization of the EMP was achieved using B-dot and D-dot probes that took measurements for a range of different target and laser parameters. We demonstrate that target stalk geometry, material composition, geodesic path length and foil surface area can all play a significant role in the reduction of EMP. A combination of electromagnetic wave and 3 D particle-in-cell simulations is used to inform our conclusions about the effects of stalk geometry on EMP,providing an opportunity for comparison with existing charge separation models.展开更多
The first demonstration of laser action in ruby was made in 1960 by T.H.Maiman of Hughes Research Laboratories,USA.Many laboratories worldwide began the search for lasers using different materials,operating at differe...The first demonstration of laser action in ruby was made in 1960 by T.H.Maiman of Hughes Research Laboratories,USA.Many laboratories worldwide began the search for lasers using different materials,operating at different wavelengths.In the UK,academia,industry and the central laboratories took up the challenge from the earliest days to develop these systems for a broad range of applications.This historical review looks at the contribution the UK has made to the advancement of the technology,the development of systems and components and their exploitation over the last 60 years.展开更多
文摘High-power laser technology is widely used in manufacturing processing,medical diagnosis,and treatment,and is one of the important fields of strategic high-tech competition in China at the moment.In the context of industrial upgrading,high-power laser technology plays an important role in leading the development of the manufacturing industry and industrial intelligence.Based on this,this paper carries out research on high-power laser technology and industry,summarizes the basic principle and classification of high-power laser technology,analyzes the current status of high-power laser technology industry,points out the opportunities and challenges faced by the industry development,puts forward suggestions to promote the development of high-power laser technology industry,and to provide an effective reference for the application and development of high-power laser technology.
基金supported by the Extreme Light Infrastructure Nuclear Physics(ELI-NP)Phase Ⅱ,a project co-financed by the Romanian Government and the European Union through the European Regional Development Fund—the Competitiveness Operational Programme(1/07.07.2016,COP,ID 1334)the Romanian Ministry of Research and Innovation:PN23210105(Phase 2,the Program Nucleu),ELI-RO grants Proiectul ELI-RO/RDI_2024_AMAP,ELI-RO_RDI_2024_LaLuThe,ELIRO_RDI_2024_SPARC+4 种基金ELI10/01.10.2020 of the Romanian Governmentthe European Union,the Romanian Governmentthe Health Program,within the project“Medical Applications of High-Power Lasers—Dr.LASER”SMIS Code:326475the IOSIN funds for research infrastructures of national interest.
文摘We propose a novel scheme for the population and depletion of nuclear isomers.This scheme combines the γ photons with energiesà 10 keV emitted during the interaction of a contemporary high-intensity laser pulse with a plasma and one or multiple photon beams supplied by intense lasers.Owing to nonlinear effects,two-or multiphoton absorption dominates over the conventional multistep one-photon process for an optimized γ flash.Moreover,this nonlinear effect can be greatly enhanced with the help of externally supplied low-energy photons coming from another laser.These low-energy photons act such that the effective cross-section experienced by the γ photons becomes tunable,growing with the intensity I_(0) of the beam.Assuming I_(0)~10^(18) W·cm^(-2) for the photon beam,an effective cross-section as large as 10^(-21)-10^(-28) cm^(2) for the γ photons can be achieved.Thus,with state-of-the-art 10 PW laser facilities,the yields from two-photon absorption can reach 10^(6)-10^(9) isomers per shot for selected states that are separated from their ground state by E2 transitions.Similar yields for transitions with higher multipolarities can be accommodated by multiphoton absorption with additional photons provided.
基金Project supported by the National Natural Science Foundation of China(Grant No.61308040)the National High Technology Research and Development Program of China(Grant No.2013AA8043047)
文摘Due to laser-induced damage, the aperture of optics is one of the main factors limiting the output capability of highpower laser facilities. Because of the general difficulty in achieving large-aperture optics, an alternative solution is to tile some small-aperture ones together. We propose an accurate, stable, and automatic method of array element tiling and verify it on a double-pass 1 × 2 tiled-grating compressor in the XG-III laser facility. The test results show the accuracy and stability of the method. This research provides an efficient way to obtain large-aperture optics for high-power laser facilities.
文摘Intensive electromagnetic pulses （EMPs） can be generated when a high-power laser strikes a target. The transient electromagnetic field can have an intensity of up to several hundred kV m- 1 with a broad frequency of up to several gigahertz, which may affect diagnostics and interfere with, or even damage, electronic equipment. In this paper, the process in which hot electrons produced by the laser-target interaction radiate EMPs is studied and simulated. The physical process is divided into three stages which are： the production of hot electrons; the escape of hot electrons; and the generation of EMPs. Instead of using a general finite difference time domain （FDTD） method to solve the Maxwell equations, a particle-in-cell method together with a time- biased FDTD method is applied in EMP simulation to restrain high-frequency noise. The results show that EMPs are stronger with higher laser intensity and larger target size.
基金Project supported by the National Natural Science Foundation of China(Grant No.61875208)。
文摘High-power laser induced thermal blooming effects in a closed chamber with three different gases are investigated theoretically and experimentally in this work. In the theoretical treatment, an incompressible gas turbulent model is adopted.In the numerical simulation the gas refractive index as a function of both the temperature and pressure is taken into consideration. In the experimental study the pump-probe technology is adopted. A high-power 1064-nm fiber laser with maximum output power of 12 k W is used to drive the gas thermal blooming, and a 50-m W high-beam-quality 637-nm laser diode(LD)is used as a probe beam. The influences of the gas thermal blooming in the chamber on the probe beam wavefront and beam quality are analyzed for three different gases of air, nitrogen, and helium, respectively. The results indicate that nitrogen is well suitable for restraining thermal blooming effect for high-power laser. The measured data are in good agreement with the simulated results.
文摘A compact, efficient and high-power laser diode （LD） single-end-pumped Nd：YVO4 laser with continuous-wave emission at 1342 nm is reported. With a single crystal single-end-pumped by fibre-coupled LD array, an output power of 7.36W is obtained from the laser cavity of concave-convex shape, corresponding to an optical-to-optical efficiency of 32.8%. The laser is operated in TEM00 mode with small rms amplitude noise of 0.3%. The influences of the Nd concentration, transmissivity of the output mirror and the cavity length on the output power have been studied experimentally.
文摘Dear Editor,I am Dr.Shan-Shan Li,from Northern Jiangsu People’s Hospital,Yangzhou,China.I write to present the case of formation of choroidal neovascularization(CNV)under the fovea after high-power laser irradiation.Currently,there is an increasing availability and accessibility to laser instruments,but improper use of these tools can lead to macular damage and irreversible visual impairment.
基金financially supported by the National Natural Science Foundation of China(Nos.51977027 and 51967008)the Scientific and Technological Project of Yunnan Precious Metals Laboratory(Nos.YPML-2023050250 and YPML-2022050206)。
文摘Lutetium aluminum garnet doped with cerium(LuAG:Ce)thin films have been identified as a promising material for high-power laser-driven lighting applications.In this study,spray pyrolysis we employed to fabricate LuAG:Ce films on sapphire substrates and the impact of film thickness on thermal management and light emission efficiency was investigated.Our results show that,regardless of thickness,LuAGiCe films exhibit impressive internal quantum efficiencies(IQE)exceeding 83.2%and external quantum efficiencies(EQE)surpassing 56.4%,with minimal alteration of luminescent color.Notably,thinner films facilitate more efficient heat dissipation to the underlying sapphire substrate,resulting in superior thermal management and outstanding luminous performance under high-power laser excitation.Specifically,the thinnest LuAG:Ce film(15.79μm)exhibited rapid thermal stabilization(~130℃ within 30s)and maintained stability during continuous irradiation lasting 30 min,with a corresponding decrease in luminous flux to 87.9%of its initial value within the first 60 s.This film also demonstrated relatively high and stable conversion efficiency and luminous efficiency,achieving higher saturation thresholds(15 W·mm^(-2))and luminous flux(1070 lm).In contrast,thicker films exhibited a shift in the saturation point toward lower power densities.These findings provide valuable insights for the practical implementation of LuAG:Ce films in advanced lighting technologies.
文摘From sevenal models about damage mechanism, the damage mechanism of optical films and the factors which affect the damage threshold are described experimentally and theoretically. Some reasonable proposals are given in this paper on how to select the high-threshold films.
基金framework of the EUROfusion Consortium,funded by the European Union via the Euratom Research and Training Programme(Grant Agreement No.101052200—EUROfusion)The CRESCO-ENEAGRID High Performance Computing infrastructure is funded by ENEA+3 种基金the Italian National Agency for New Technologies,Energy and Sustainable Economic Developmentby Italian and European research programmesthe framework of the“Universities’Excellence Initiative”programme by the Ministry of Education,Science and Sports of the Republic of Lithuania under an agreement with the Research Council of Lithuania(Project No.S-A-UEI-23-6)support was received through EU LASERLAB-EUROPE JRAextension(Grant Agreement No.871124,Horizon 2020 Research and Innovation Programme).
文摘Inertial confinement fusion(ICF)requires a constant search for the most effective materials to improve the efficiency of compression of the capsule and of laser-to-target energy transfer.Foams could provide a solution,but they require further experimental and theoretical investigation.The new 3D-printing technologies,such as two-photon polymerization,are opening a new era in the production of foams,allowing fine control of material morphology.Very few detailed studies of the interaction of foams with high-power lasers in regimes relevant for ICF have been described in the literature to date,and more investigation is needed.In this work,we present the results of an experimental campaign performed at the ABC laser facility at ENEA Centro Ricerche Frascati in which 3D-printed microstructured materials were irradiated at high power.3D simulations of the laser-target interaction performed with the FLASH code reveal that the laser is scattered by plasma density gradients and channeled into the structure when the center of the focal spot is on the through hole.The time required for the laser to completely ablate the structure given by the simulations is in good agreement with the experimental measurement.Measurements of the reflected and transmitted laser light indicate that scattering occurred during the irradiation,in accordance with the simulations.Two-plasmon decay has also been found to be active during irradiation.
基金supported by the Project of the Ministry of Industry and Information Technology(Grant No.TC220H05L)the National Natural Science Foundation of China(NSFC)(Grant Nos.61905261,61827816 and 11875308)+1 种基金the Shanghai Sailing Program(Grant No.18YF1426600)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA25020306).
文摘Accurate characterization of high-power laser parameters,especially the near-field and far-field distributions,is crucial for inertial confinement fusion experiments.In this paper,we propose a method for computationally reconstructing the complex amplitude of high-power laser beams using modified coherent modulation imaging.This method has the advantage of being able to simultaneously calculate both the near-field(intensity and wavefront/phase)and far-field(focal-spot)distributions using the reconstructed complex amplitude.More importantly,the focal-spot distributions at different focal planes can also be calculated.To verify the feasibility,the complex amplitude optical field of the highpower pulsed laser was measured after static aberrations calibration.Experimental results also indicate that the near-field wavefront resolution of this method is higher than that of the Hartmann measurement.In addition,the far-field focal spot exhibits a higher dynamic range(176 dB)than that of traditional direct imaging(62 dB).
基金funding from the EU Horizon 2020 Eu PRAXIA Preparatory Phase,under Grant Agreement No.101079773,and EU Horizon IFAST,under Grant Agreement No.101004730co-funded by the European Union–Next Generation EU‘Integrated infrastructure initiative in Photonic and Quantum Sciences’–I-PHOQS(IR0000016,ID D2B8D520,CUP B53C22001750006)and‘Eu PRAXIA Advanced Photon Sources’–Eu APS(IR0000030,CUP I93C21000160006)the funding from the National Research,Development,and Innovation Office through the National Laboratory program(contract#NKFIH 877-2/2020,and 476-4/2021)。
文摘Accelerator-driven systems(ADSs)may offer a promising technology for energy production and transmutation of nuclear waste.Here we introduce the concept of utilizing high-intensity laser acceleration technology in realizing an ADS,with a focus on the use of thorium fuel in subcritical systems.We explore state-of-the-art laser-driven particle sources for neutron generation by nuclear fusion,spallation or photonuclear reactions and the prospect of reaching the flux of 10^(15)n/s required to drive a subcritical reactor.We review recent advances in high-power laser amplification and assess their technological readiness in view of integration in an ADS.Finally,we present a risk analysis of a laser-driven ADS in terms of laser and target development,radiation safety and operational stability.Our conclusion highlights the potential of laser-driven ADSs as a transformative approach to nuclear fission energy.With continued research and development,technological hurdles can be overcome to fully realize sustainable,green energy production that can meet global energy demands while addressing safety and environmental concerns.
文摘Cladding light strippers(CLSs)are essential components for high-power monolithic fiber laser systems.Because they allow for bending of the fiber,which leads to an excellent stripping efficiency of light with a low ray angle,refractive index-based CLSs have an advantage over the commonly used alternative approaches.However,conventional high-index CLSs overheat at relatively low input power as the maximum temperature,located in a hot-spot,increases linearly with the input power.This applies particularly to CLSs in thulium-based fiber systems,where very low power can already lead to extreme heat generation due to the high cladding material absorption around 2μm.Here,we investigate materials with a highly negative thermooptical coefficient combined with a refractive index closely above glass to distribute the stripped power and heat uniformly along an increased fiber length.Analyzing multiple CLS geometries for fiber diameters of 125 and 400μm,we show record-high maximum input powers for single-material CLSs of 21.8 W for the signal(2039 nm)and 675 W for the pump wavelength(793 nm).Transmitting excess light instead of overheating,this wavelength-adaptable self-protecting CLS concept is fast to apply onsite in the lab and reaches stripping efficiencies of>40 dB in the bent version.
文摘The authors report the development of aλ~4.1μm quantum cascade laser grown by metal-organic chemical vapor deposition using strain-balanced In Ga As/In Al As materials.A device with a 7.5 mm cavity length and 6.5μm ridge width,bonded to an aluminum nitride heatsink,achieves maximum output powers of 3.4 W at 288 K in pulsed mode and 1.6 W at288 K in continuous-wave(CW)operation,with corresponding maximum wall-plug efficiencies of 14.8%and 9.3%.A kink is observed in the power–current curve under CW operation,which is absent in pulsed operation.Near-field results show that in CW operation,the horizontal beam quality factor M2fluctuates with current,indicating mode instability and highorder lateral mode excitation,while in pulsed mode,the horizontal M2remains stable around 1.3 as the current increases from 1.4 A to 1.9 A.
基金the Czech Ministry of Education,Youth and Sports(CMEYS)for the financial support of the project No.LM2023068(PALS RI)the Grant Agency of the Czech Republic(Project No.GM23-05027M)。
文摘A large laser spark was produced in a homogeneous sulphur hexafluoride gas(pressures ranged from 10.7 to 101.3 kPa)by a focused high-power laser pulse(350 ps,125 J,1315.2 nm).Magnetic fields,electromagnetic pulses(EMPs),optical emission spectra(OES)and chemical changes associated with the laser-induced dielectric breakdown(LIDB)in the SF6 gas were investigated.During the laser interaction,hot electrons escaping the plasma kernel produced EMPs and spontaneous magnetic fields,the frequency spectrum of which contains three bands around 1.15,2.1 and 3 GHz,while the EMP frequency band appeared around 1.1 GHz.The EMP emission from a laser spark was very weak in comparison to those generated at a solid target.Gas chromatography revealed the formation of only a limited number of products and a low degree of sulphur hexafluoride(SF_(6))conversion.OES diagnosed the LIDB plasma in the phase of its formation as well as during its recombination.
基金supported by the Office of Science,Office of High Energy Physics,of the US Department of Energythe Laboratory Directed Research and Development Program of Lawrence Berkeley National Laboratory under contract No.DE-AC02-05CH11231。
文摘High-power lasers are vital for particle acceleration,imaging,fusion and materials processing,requiring precise control and high-energy delivery.Laser plasma accelerators(LPAs)demand laser positional stability at focus to ensure consistent electron beams in applications such as X-ray free-electron lasers and high-energy colliders.Achieving this stability is especially challenging for the low-repetition-rate lasers in current LPAs.We present a machine learning method that predicts and corrects laser pointing instabilities in real-time using a high-frequency pilot beam.By preemptively adjusting a correction mirror,this approach overcomes traditional feedback limits.Demonstrated on the BELLA petawatt laser operating at the terawatt level(30 mJ amplification),our method achieved root mean square pointing stabilization of 0.34 and 0.59μrad in the x and y directions,reducing jitter by 65%and 47%,respectively.This is the first successful application of predictive control for shot-to-shot stabilization in low-repetition-rate laser systems,paving the way for full-energy petawatt lasers and transformative advances across science,industry and security.
基金National Natural Science Foundation of China(62005004,61675009)Natural Science Foundation of Beijing Municipality(4204091,KZ201910005006)China Postdoctoral Science Foundation(212423)。
文摘Ultra-broadband supercontinuum(SC)lasers covering the mid-infrared(MIR)region have significant applications in trace substance detection,national defense,and biomedical fields.Currently,high-power SC spanning2–5μm is still dominated by traditional fluoride(InF_(3))fibers.Although tellurite fibers,with their excellent chemical and thermal stability,have demonstrated significantly higher power scalability compared to other MIR fibers,their spectral broadening capabilities in the 4–5μm region remain largely unexplored.Here,we demonstrate a>10 W ultra-broadband flat SC spanning the 1.8–5.1μm spectral range in a fluorotellurite fiber using a cascaded soliton self-frequency shifting technique.The fluorotellurite fiber is precisely tapered to reconstruct dispersion and nonlinearity,which facilitates the evolution of the pre-stage Raman soliton into higherorder solitons,thereby enabling a new round of“rapid relay fission.”At a low pump power of 7.5 W,we also achieved a high-power(0.5 W)Raman soliton(60 fs)at 4.3μm.These results,for the first time,to our knowledge,demonstrate that tapered fluorotellurite fibers can be used for high-power femtosecond pulse generation beyond4μm and high-power SC generation beyond 5μm,establishing them as an exceptional nonlinear medium for the development of high-power MIR fiber lasers in the 4–5μm spectral region.
基金Project (51175095) supported by the National Natural Science Foundation of ChinaProjects (10251009001000001,9151009001000020) supported by the Natural Science Foundation of Guangdong Province,ChinaProject (20104420110001) supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China
文摘Classification of plume and spatter images was studied to evaluate the welding stability. A high-speed camera was used to capture the instantaneous images of plume and spatters during high power disk laser welding. Characteristic parameters such as the area and number of spatters, the average grayscale of a spatter image, the entropy of a spatter grayscale image, the coordinate ratio of the plume centroid and the welding point, the polar coordinates of the plume centroid were defined and extracted. Karhunen-Loeve transform method was used to change the seven characteristics into three primary characteristics to reduce the dimensions. Also, K-nearest neighbor method was used to classify the plume and spatter images into two categories such as good and poor welding quality. The results show that plume and spatter have a close relationship with the welding stability, and two categories could be recognized effectively using K-nearest neighbor method based on Karhunen-Loeve transform.
基金funding from EPSRC grants EP/L01663X/1 and EP/L000644/1the Newton UK grant+1 种基金the National Natural Science Foundation of China NSFC/11520101003the LLNL Academic Partnership in ICF
文摘Giant electromagnetic pulses(EMP) generated during the interaction of high-power lasers with solid targets can seriously degrade electrical measurements and equipment. EMP emission is caused by the acceleration of hot electrons inside the target, which produce radiation across a wide band from DC to terahertz frequencies. Improved understanding and control of EMP is vital as we enter a new era of high repetition rate, high intensity lasers(e.g. the Extreme Light Infrastructure).We present recent data from the VULCAN laser facility that demonstrates how EMP can be readily and effectively reduced. Characterization of the EMP was achieved using B-dot and D-dot probes that took measurements for a range of different target and laser parameters. We demonstrate that target stalk geometry, material composition, geodesic path length and foil surface area can all play a significant role in the reduction of EMP. A combination of electromagnetic wave and 3 D particle-in-cell simulations is used to inform our conclusions about the effects of stalk geometry on EMP,providing an opportunity for comparison with existing charge separation models.
文摘The first demonstration of laser action in ruby was made in 1960 by T.H.Maiman of Hughes Research Laboratories,USA.Many laboratories worldwide began the search for lasers using different materials,operating at different wavelengths.In the UK,academia,industry and the central laboratories took up the challenge from the earliest days to develop these systems for a broad range of applications.This historical review looks at the contribution the UK has made to the advancement of the technology,the development of systems and components and their exploitation over the last 60 years.
