High-average-power strong-field terahertz(THz)pulses,which are generated via the optical rectification of 100-W average-power ytterbium(Yb)lasers in a nonlinear crystal,have been used to study extreme physical phenome...High-average-power strong-field terahertz(THz)pulses,which are generated via the optical rectification of 100-W average-power ytterbium(Yb)lasers in a nonlinear crystal,have been used to study extreme physical phenomena and realize various applications.However,this THz generation method suffers from a trade-off in which high repetition rates lead to low optical-to-THz energy conversion efficiency,as well as the risk of damage to the crystals under high average pumping power.In this study,we demonstrate a high-averagepower,high-repetition-rate,strong-field THz source in lithium niobate driven by a 1030 nm,1 ps,2 mJ,100 kHz Yb femtosecond laser with a tilted-pulse front-pumping configuration.By characterizing two key experimental parameters,namely the pump spot size and pulse duration,we achieve,to the best of our knowledge,the highest THz average power of 104mW at 100 kHz,with a conversion efficiency of 0.1%and without any cooling operation at room temperature.In addition,a strong electric field of 421 kV/cm is achieved at 1 kHz.Our THz system directly demonstrates its potential capabilities in high-signal-to-noise spectroscopy,imaging,nondestructive testing,and relevant THz applications.展开更多
Poly-L-lactide（PLLA） was synthesized by ring-opening polymerization fi＇om high purity L-lactide with tin octoate as initiator, and characterized by means of infi＇ared, and ^1H-nuclear magnetic resonance. The influ...Poly-L-lactide（PLLA） was synthesized by ring-opening polymerization fi＇om high purity L-lactide with tin octoate as initiator, and characterized by means of infi＇ared, and ^1H-nuclear magnetic resonance. The influences of initiator concentration, polymerization temperature and polymerization time on the viscosity average molecular mass of PLLA were investigated. The effects of different purification methods on the concentration of initiator and viscosity average molecular mass were also studied. PLLA with a viscosity average molecular mass of about 50.5×1^04 was obtained when polymerization was conducted for 24 h at 140℃ with the molar ratio of monomer to purification initator being 12 000. After purification, the concentration of tin octoate decreases; however, the effect of different purification methods on the viscosity average molecular mass of PLLA is different, and the obtained PLLA is a typical amorphous polymeric material. The crystallinity of PLLA decreases with the increase of viscosity average molecular mass.展开更多
Free-space strong-field terahertz(THz)pulses,generated via optical rectification of femtosecond lasers in nonlinear crystals,are pivotal in various applications.However,conventional Ti:sapphire lasers struggle to prod...Free-space strong-field terahertz(THz)pulses,generated via optical rectification of femtosecond lasers in nonlinear crystals,are pivotal in various applications.However,conventional Ti:sapphire lasers struggle to produce high-average-power THz sources due to their limited output power.While kilowatt ytterbium lasers are increasingly adopted,their application in THz generation faces challenges:low optical-to-THz conversion efficiency(attributed to long pulse duration and low energy)and crystal damage under high pumping power.Here,we report a high-average-power strong-field THz source using a lithium niobate crystal pumped by a 1030 nm,570 fs,1 mJ,50 kHz ytterbium femtosecond laser with tilted pulse front pumping(TPFP).By systematically optimizing TPFP implementations and comparing grating-and echelon-type configurations,we achieve a THz source with 64.5 mW average power at 42 W,50 kHz pumping,and focused peak electric field of 525 kV/cm at 0.83 mJ,1 kHz operation.Additionally,we observe Zeeman torque signals in cobalt-iron ferromagnetic nanofilms.This high-repetition-rate,high-average-power THz system,combined with its potential capabilities in high signal-to-noise ratio spectroscopy and imaging,promises transformative impacts in quantum matter manipulation,non-destructive testing,and biomedicine.展开更多
We present a cascaded nonlinear spectral broadening scheme for Nd-doped lasers,featuring with long pulse duration and high average power.This scheme is based on two multi-pass cells(MPCs)and one multiple-plate superco...We present a cascaded nonlinear spectral broadening scheme for Nd-doped lasers,featuring with long pulse duration and high average power.This scheme is based on two multi-pass cells(MPCs)and one multiple-plate supercontinuum generation(MPSG),and the numerical investigation is driven by a home-made Nd-doped fiber laser with 12 ps pulse duration,50 kHz repetition rate and 100 W average power.The MPC-based first two stages allow us to broaden the pulse spectrum to 4 nm and 43 nm respectively,and subsequently,the MPSG-based third stage allows us to reach 235 nm spectral bandwidth.This broadened spectrum can support a Fourier-transfer-limited pulse duration of 9.8 fs,which is shorter than three optical cycles.To the best of our knowledge,it is the first time to demonstrate the possibility of few-cycle pulses generation based on the 10 ps level Nd-doped lasers.Such few-cycle and high average power laser sources should be attractive and prospective,benefiting from the characteristics of structure compact,low-cost and flexibility.展开更多
The process of high harmonic generation(HHG)enables the development of table-top sources of coherent extreme ultraviolet(XUV)light.Although these are now matured sources,they still mostly rely on bulk laser technology...The process of high harmonic generation(HHG)enables the development of table-top sources of coherent extreme ultraviolet(XUV)light.Although these are now matured sources,they still mostly rely on bulk laser technology that limits the attainable repetition rate to the low kilohertz regime.Moreover,many of the emerging applications of such light sources(e.g.,photoelectron spectroscopy and microscopy,coherent diffractive imaging,or frequency metrology in the XUV spectral region)require an increase in the repetition rate.Ideally,these sources are operated with a multi-MHz repetition rate and deliver a high photon flux simultaneously.So far,this regime has been solely addressed using passive enhancement cavities together with low energy and high repetition rate lasers.Here,a novel route with significantly reduced complexity(omitting the requirement of an external actively stabilized resonator)is demonstrated that achieves the previously mentioned demanding parameters.A krypton-filled Kagome photonic crystal fiber is used for efficient nonlinear compression of 9 μJ,250 fs pulses leading to,7 μJ,31 fs pulses at 10.7 MHz repetition rate.The compressed pulses are used for HHG in a gas jet.Particular attention is devoted to achieving phase-matched(transiently)generation yielding.10^(13) photons s^(-1)(.50 μW)at 27.7 eV.This new spatially coherent XUV source improved the photon flux by four orders of magnitude for direct multi-MHZ experiments,thus demonstrating the considerable potential of this source.展开更多
A high-power all polarization-maintaining(PM) chirped pulse amplification(CPA) system operating in the 2.0 μm range is experimentally demonstrated.Large mode area(LMA) thulium-doped fiber(TDF) with a core/cladding di...A high-power all polarization-maintaining(PM) chirped pulse amplification(CPA) system operating in the 2.0 μm range is experimentally demonstrated.Large mode area(LMA) thulium-doped fiber(TDF) with a core/cladding diameter of25/400 μm is employed to construct the main amplifier.Through dedicated coiling and cooling of the LMA-TDF to manage the loss of the higher order mode and thermal effect,a maximum average power of 314 W with a slope efficiency of 52% and polarization extinction ratio of 20 dB is realized.The pulse duration is compressed to 283 fs with a grating pair,corresponding to a calculated peak power of 10.8 MW,considering the compression efficiency of 88% and the estimated Strehl ratio of 89%.Moreover,through characterizing the noise properties of the laser,an integrated relative intensity noise of 0.11% at 100 Hz-1 MHz is obtained at the maximum output power,whereas the laser timing jitter is degraded by the final amplifier from 318 to 410 fs at an integration frequency of 5 kHz to 1 MHz,owing to the self-phase modulation effect-induced spectrum broadening.The root-mean-square of long-term power fluctuation is tested to be0.6%,verifying the good stability of the laser operation.To the best of our knowledge,this is the highest average power of an ultrafast laser realized from an all-PM-fiber TDF-CPA system ever reported.展开更多
We report on frequency doubling of high-energy,high repetition rate ns pulses from a cryogenically gas cooled multi-slab ytterbium-doped yttrium aluminum garnet laser system,Bivoj/DiPOLE,using a type-I phase matched l...We report on frequency doubling of high-energy,high repetition rate ns pulses from a cryogenically gas cooled multi-slab ytterbium-doped yttrium aluminum garnet laser system,Bivoj/DiPOLE,using a type-I phase matched lithium triborate crystal.We achieved conversion to 515 nm with energy of 95 J at repetition rate of 10 Hz and conversion efficiency of 79%.High conversion efficiency was achieved due to successful depolarization compensation of the fundamental input beam.展开更多
We report the characterization of the pump absorption and emission dynamic properties of a Tm:Lu2O3 ceramic lasing medium using a three-mirror folded laser cavity.We measured a slope efficiency of 73%,which allowed us...We report the characterization of the pump absorption and emission dynamic properties of a Tm:Lu2O3 ceramic lasing medium using a three-mirror folded laser cavity.We measured a slope efficiency of 73%,which allowed us to retrieve the cross-relaxation coefficient.The behavior of our system was modeled via a set of macroscopic rate equations in both the quasi continuous wave and the pulsed pumping regime.Numerical solutions were obtained,showing a good agreement with the experimental findings.The numerical solution also yielded a cross-relaxation coefficient in very good agreement with the measured one,showing that the cross-relaxation phenomenon approaches the maximum theoretical efficiency.展开更多
The Mamyshev oscillator(MO)is well-known for its high modulation depth,which provides an excellent platform for achieving both high average power and short pulse durations.However,this characteristic typically limits ...The Mamyshev oscillator(MO)is well-known for its high modulation depth,which provides an excellent platform for achieving both high average power and short pulse durations.However,this characteristic typically limits the highrepetition-rate pulse generation.Herein,we construct an MO that achieves a gigahertz(GHz)repetition rate through harmonic mode-locking.The laser can reach up to the 93rd order,which corresponds to the repetition rate of 1.6 GHz.The maximum achieved output average power is 3 W at a repetition rate of 1.2 GHz(69th order),with the corresponding pulse duration compressed to 51 fs.To our knowledge,this is the first time that the GHz repetition rate in an MO has been obtained simultaneously with the recorded average power and pulse duration.展开更多
A 2.05μm holmium-doped yttrium lithium fluoride(Ho:YLF)master oscillator power amplifier system with both high average power and high pulse energy operating at a 1 kHz repetition rate is demonstrated,achieving a maxi...A 2.05μm holmium-doped yttrium lithium fluoride(Ho:YLF)master oscillator power amplifier system with both high average power and high pulse energy operating at a 1 kHz repetition rate is demonstrated,achieving a maximum output power of 280 W with a pulse width of 14.5 ns.The system comprises three-stage amplifiers,boosting a 20 W seed laser to output powers of 110,205 and 280 W,corresponding to extraction efficiencies of 46.1%,45.0%and 34.9%,respectively.At maximum output,the system exhibits excellent beam quality(M_(x)^(2)=1.22 and M_(y)^(2)=1.23)and power stability(root mean square=0.5%over 30 min).To the best of our knowledge,this work reports the highest pulse energy(280 mJ)achieved for a 2μm laser operating at a kHz repetition rate.In addition,a slice model of an end-pumped quasi-three-level laser amplifier was developed to analyze the output limitations of multi-stage Ho:YLF amplifiers based on rod geometry,providing theoretical support for the experimental results.展开更多
Since the advent of femtosecond lasers,performance improvements have constantly impacted on existing applications and enabled novel applications.However,one performance feature bearing the potential of a quantum leap ...Since the advent of femtosecond lasers,performance improvements have constantly impacted on existing applications and enabled novel applications.However,one performance feature bearing the potential of a quantum leap for high-field applications is still not available:the simultaneous emission of extremely high peak and average powers.Emerging applications such as laser particle acceleration require exactly this performance regime and,therefore,challenge laser technology at large.On the one hand,canonical bulk systems can provide pulse peak powers in the multi-terawatt to petawatt range,while on the other hand,advanced solid-state-laser concepts such as the thin disk,slab or fibre are well known for their high efficiency and their ability to emit high average powers in the kilowatt range with excellent beam quality.In this contribution,a compact laser system capable of simultaneously providing high peak and average powers with high wall-plug efficiency is proposed and analysed.The concept is based on the temporal coherent combination(pulse stacking)of a pulse train emitted from a high-repetition-rate femtosecond laser system in a passive enhancement cavity.Thus,the pulse energy is increased at the cost of the repetition rate while almost preserving the average power.The concept relies on a fast switching element for dumping the enhanced pulse out of the cavity.The switch constitutes the key challenge of our proposal.Addressing this challenge could,for the first time,allow the highly efficient dumping of joule-class pulses at megawatt average power levels and lead to unprecedented laser parameters.展开更多
Mamyshev oscillators (MOs) exhibit the potential for generating high average power and ultrashort pulses. Herein,we construct an MO using flexible double-cladding ytterbium-fiber with a fusion-spliced-combiner pumped ...Mamyshev oscillators (MOs) exhibit the potential for generating high average power and ultrashort pulses. Herein,we construct an MO using flexible double-cladding ytterbium-fiber with a fusion-spliced-combiner pumped scheme.Consistent with the most reported research results, the offset filter separation significantly affects the pulse characteristics(spectrum, pulse duration, etc.). Notably, in comparison with red-shifting, blue-shifting the peak spectral emission of the grating filter relative to a constant central wavelength of the bandpass filter substantially enhances the laser output characteristics. This phenomenon, which has not been previously reported, results in an average power up to 2.23 W and a pulse duration as short as 49 fs. To our knowledge, this is the highest average power achieved in sub-50 fs pulse duration in the nonlinear polarization rotation-assisted mode-locked MO laser architecture. The presented technique offers unique scientific proof for developing ultrafast laser sources with higher average power and shorter pulse duration.展开更多
We present a study of second harmonic generation(SHG) and third harmonic generation(THG) in lithium triborate(LBO) crystals using a high-energy,10-J-class,10 Hz ytterbium-doped yttrium aluminum garnet laser system.We ...We present a study of second harmonic generation(SHG) and third harmonic generation(THG) in lithium triborate(LBO) crystals using a high-energy,10-J-class,10 Hz ytterbium-doped yttrium aluminum garnet laser system.We achieved high conversion efficiencies of 75% for SHG and 56% for THG for Gaussian-like temporal pulse shapes and top-hat-like beam profiles.The angular and temperature dependence of the LBO crystals was measured and validated through numerical simulations.The SHG process exhibited an angular acceptance bandwidth of 1.33 mrad and a temperature acceptance bandwidth of 2.61 K,while the THG process showed 1.19 mrad and 1.35 K,respectively.In addition,long-term stability measurements revealed root mean square energy stabilities of 1.3% for SHG and 1.24% for THG.These results showcase the reliability of LBO crystals for high-energy,high-average-power harmonic generation.The developed system offers automated switching between harmonics provided at the system output.The system can be easily adapted to neodymium-doped yttrium aluminum garnet based pump lasers as well.展开更多
基金supported by the Scientific Research Innovation Capability Support Project for Young Faculty(Grant No.ZYGXQNJSKYCXNLZCXM-I3)the National Key Research and Development Program of China(Grant No.2022YFA1604402)+1 种基金the National Natural Science Foundation of China(Grant Nos.U23A6002 and 92250307)the Beijing Municipal Science&Technology Commission,Administrative Commission of Zhongguancun Science Park(Grant No.Z251100006925005)。
文摘High-average-power strong-field terahertz(THz)pulses,which are generated via the optical rectification of 100-W average-power ytterbium(Yb)lasers in a nonlinear crystal,have been used to study extreme physical phenomena and realize various applications.However,this THz generation method suffers from a trade-off in which high repetition rates lead to low optical-to-THz energy conversion efficiency,as well as the risk of damage to the crystals under high average pumping power.In this study,we demonstrate a high-averagepower,high-repetition-rate,strong-field THz source in lithium niobate driven by a 1030 nm,1 ps,2 mJ,100 kHz Yb femtosecond laser with a tilted-pulse front-pumping configuration.By characterizing two key experimental parameters,namely the pump spot size and pulse duration,we achieve,to the best of our knowledge,the highest THz average power of 104mW at 100 kHz,with a conversion efficiency of 0.1%and without any cooling operation at room temperature.In addition,a strong electric field of 421 kV/cm is achieved at 1 kHz.Our THz system directly demonstrates its potential capabilities in high-signal-to-noise spectroscopy,imaging,nondestructive testing,and relevant THz applications.
基金Project (50174059) supported by the National Natural Science Foundation of China
文摘Poly-L-lactide（PLLA） was synthesized by ring-opening polymerization fi＇om high purity L-lactide with tin octoate as initiator, and characterized by means of infi＇ared, and ^1H-nuclear magnetic resonance. The influences of initiator concentration, polymerization temperature and polymerization time on the viscosity average molecular mass of PLLA were investigated. The effects of different purification methods on the concentration of initiator and viscosity average molecular mass were also studied. PLLA with a viscosity average molecular mass of about 50.5×1^04 was obtained when polymerization was conducted for 24 h at 140℃ with the molar ratio of monomer to purification initator being 12 000. After purification, the concentration of tin octoate decreases; however, the effect of different purification methods on the viscosity average molecular mass of PLLA is different, and the obtained PLLA is a typical amorphous polymeric material. The crystallinity of PLLA decreases with the increase of viscosity average molecular mass.
基金Scientific Research Innovation Capability Support Project for Young(ZYGXQNJSKYCXNLZCXMI3)National Key Research and Development Program of China(2022YFA1604402)+1 种基金National Natural Science Foundation of China(U23A6002,92250307)Open Project Program of Wuhan National Laboratory for Optoelectronics(2022WNLOKF006)。
文摘Free-space strong-field terahertz(THz)pulses,generated via optical rectification of femtosecond lasers in nonlinear crystals,are pivotal in various applications.However,conventional Ti:sapphire lasers struggle to produce high-average-power THz sources due to their limited output power.While kilowatt ytterbium lasers are increasingly adopted,their application in THz generation faces challenges:low optical-to-THz conversion efficiency(attributed to long pulse duration and low energy)and crystal damage under high pumping power.Here,we report a high-average-power strong-field THz source using a lithium niobate crystal pumped by a 1030 nm,570 fs,1 mJ,50 kHz ytterbium femtosecond laser with tilted pulse front pumping(TPFP).By systematically optimizing TPFP implementations and comparing grating-and echelon-type configurations,we achieve a THz source with 64.5 mW average power at 42 W,50 kHz pumping,and focused peak electric field of 525 kV/cm at 0.83 mJ,1 kHz operation.Additionally,we observe Zeeman torque signals in cobalt-iron ferromagnetic nanofilms.This high-repetition-rate,high-average-power THz system,combined with its potential capabilities in high signal-to-noise ratio spectroscopy and imaging,promises transformative impacts in quantum matter manipulation,non-destructive testing,and biomedicine.
基金Project supported by the National Natural Science Foundation of China(Grant No.61925507)the National Key R&D Program of China(Grant No.2017YFE0123700)+5 种基金the Strategic Priority Research Program of Chinese Academic Sciences(Grant No.XDB1603)the Shanghai Municipal Science and Technology Major Project(Grant No.2017SHZDZX02)the Shanghai Natural ScienceFoundation(Grant No.20ZR1464600)the Program of Shanghai Academic/Technology Research Leader(Grant No.18XD1404200)the Shanghai Sailing Program(Grant No.21YF1453800)Youth Innovation Promotion Association of Chinese Academic Sciences(Grant No.Y202059).
文摘We present a cascaded nonlinear spectral broadening scheme for Nd-doped lasers,featuring with long pulse duration and high average power.This scheme is based on two multi-pass cells(MPCs)and one multiple-plate supercontinuum generation(MPSG),and the numerical investigation is driven by a home-made Nd-doped fiber laser with 12 ps pulse duration,50 kHz repetition rate and 100 W average power.The MPC-based first two stages allow us to broaden the pulse spectrum to 4 nm and 43 nm respectively,and subsequently,the MPSG-based third stage allows us to reach 235 nm spectral bandwidth.This broadened spectrum can support a Fourier-transfer-limited pulse duration of 9.8 fs,which is shorter than three optical cycles.To the best of our knowledge,it is the first time to demonstrate the possibility of few-cycle pulses generation based on the 10 ps level Nd-doped lasers.Such few-cycle and high average power laser sources should be attractive and prospective,benefiting from the characteristics of structure compact,low-cost and flexibility.
基金This work was partly supported by the German Federal Ministry of Education and Research(BMBF)the European Research Council under the European Union’s Seventh Framework Programme(FP7/2007-2013)/ERC Grant Agreement No.240460Arno Klenke and Jan Rothhardt acknowledge financial support by the Helmholtz-Institute Jena.
文摘The process of high harmonic generation(HHG)enables the development of table-top sources of coherent extreme ultraviolet(XUV)light.Although these are now matured sources,they still mostly rely on bulk laser technology that limits the attainable repetition rate to the low kilohertz regime.Moreover,many of the emerging applications of such light sources(e.g.,photoelectron spectroscopy and microscopy,coherent diffractive imaging,or frequency metrology in the XUV spectral region)require an increase in the repetition rate.Ideally,these sources are operated with a multi-MHz repetition rate and deliver a high photon flux simultaneously.So far,this regime has been solely addressed using passive enhancement cavities together with low energy and high repetition rate lasers.Here,a novel route with significantly reduced complexity(omitting the requirement of an external actively stabilized resonator)is demonstrated that achieves the previously mentioned demanding parameters.A krypton-filled Kagome photonic crystal fiber is used for efficient nonlinear compression of 9 μJ,250 fs pulses leading to,7 μJ,31 fs pulses at 10.7 MHz repetition rate.The compressed pulses are used for HHG in a gas jet.Particular attention is devoted to achieving phase-matched(transiently)generation yielding.10^(13) photons s^(-1)(.50 μW)at 27.7 eV.This new spatially coherent XUV source improved the photon flux by four orders of magnitude for direct multi-MHZ experiments,thus demonstrating the considerable potential of this source.
基金supported by the Director Fund of State Key Laboratory of Pulsed Power Laser Technology(No.SKL2020ZR02)the Postgraduate Scientific Research Innovation Project of Hunan Province(No.QL20210015).
文摘A high-power all polarization-maintaining(PM) chirped pulse amplification(CPA) system operating in the 2.0 μm range is experimentally demonstrated.Large mode area(LMA) thulium-doped fiber(TDF) with a core/cladding diameter of25/400 μm is employed to construct the main amplifier.Through dedicated coiling and cooling of the LMA-TDF to manage the loss of the higher order mode and thermal effect,a maximum average power of 314 W with a slope efficiency of 52% and polarization extinction ratio of 20 dB is realized.The pulse duration is compressed to 283 fs with a grating pair,corresponding to a calculated peak power of 10.8 MW,considering the compression efficiency of 88% and the estimated Strehl ratio of 89%.Moreover,through characterizing the noise properties of the laser,an integrated relative intensity noise of 0.11% at 100 Hz-1 MHz is obtained at the maximum output power,whereas the laser timing jitter is degraded by the final amplifier from 318 to 410 fs at an integration frequency of 5 kHz to 1 MHz,owing to the self-phase modulation effect-induced spectrum broadening.The root-mean-square of long-term power fluctuation is tested to be0.6%,verifying the good stability of the laser operation.To the best of our knowledge,this is the highest average power of an ultrafast laser realized from an all-PM-fiber TDF-CPA system ever reported.
基金This work was supported by the European Regional Development Fund and the state budget of the Czech Republic project HiLASE CoE(CZ.02.1.01/0.0/0.0/15_006/0000674)the Horizon 2020 Framework Programme(H2020)(739573).
文摘We report on frequency doubling of high-energy,high repetition rate ns pulses from a cryogenically gas cooled multi-slab ytterbium-doped yttrium aluminum garnet laser system,Bivoj/DiPOLE,using a type-I phase matched lithium triborate crystal.We achieved conversion to 515 nm with energy of 95 J at repetition rate of 10 Hz and conversion efficiency of 79%.High conversion efficiency was achieved due to successful depolarization compensation of the fundamental input beam.
基金EU Horizon 2020 Research and Innovation Program EuPRAXIA Preparatory Phase,under Grant Agreement No.101079773,EU Horizon IFAST,under Grant Agreement No.101004730This research has been co-funded by the European Union-NextGeneration EU‘Integrated infrastructure initiative in Photonic and Quantum Sciences’-I-PHOQS(IR0000016,ID D2B8D520,CUP B53C22001750006)+1 种基金‘EuPRAXIA Advanced Photon Sources’-EuAPS(IR0000030,CUP I93C21000160006)the Project‘Tuscany Health Ecosystem-THE’‘Spoke 1-Advanced Radiotherapies and Diagnostics in Oncology’funded by the NextGenerationEU(PNRR),Codice progetto ECS00000017,D.D.MUR No.105523 May 2022.
文摘We report the characterization of the pump absorption and emission dynamic properties of a Tm:Lu2O3 ceramic lasing medium using a three-mirror folded laser cavity.We measured a slope efficiency of 73%,which allowed us to retrieve the cross-relaxation coefficient.The behavior of our system was modeled via a set of macroscopic rate equations in both the quasi continuous wave and the pulsed pumping regime.Numerical solutions were obtained,showing a good agreement with the experimental findings.The numerical solution also yielded a cross-relaxation coefficient in very good agreement with the measured one,showing that the cross-relaxation phenomenon approaches the maximum theoretical efficiency.
基金supported by the National Natural Science Foundation of China(NSFC)(Grant No.12164030)the Young Science and Technology Talents of Inner Mongolia(Grant No.NJYT22101)+1 种基金the Central Government Guides Local Science and Technology Development Fund Projects(Grant No.2023ZY0005)the Science and Technology Plan Projects of Inner Mongolia Autonomous Region of China(Grant No.2023KYPT0012)。
文摘The Mamyshev oscillator(MO)is well-known for its high modulation depth,which provides an excellent platform for achieving both high average power and short pulse durations.However,this characteristic typically limits the highrepetition-rate pulse generation.Herein,we construct an MO that achieves a gigahertz(GHz)repetition rate through harmonic mode-locking.The laser can reach up to the 93rd order,which corresponds to the repetition rate of 1.6 GHz.The maximum achieved output average power is 3 W at a repetition rate of 1.2 GHz(69th order),with the corresponding pulse duration compressed to 51 fs.To our knowledge,this is the first time that the GHz repetition rate in an MO has been obtained simultaneously with the recorded average power and pulse duration.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA0380205)the Shanghai Collaborative Innovation Program(Grant No.XTCX-KJ-2024-41)+4 种基金the Shanghai RisingStar Program(Grant No.24YF2752900)the China Postdoctoral Science Foundation(Grant No.2025T180227)the Talent Plan of the Shanghai Branch,Chinese Academy of Sciencesthe National Key Research and Development Program of China(Grant No.2022YFA1604401)the National Natural Science Foundation of China(Grant Nos.12388102,22227901 and U21A20138)
文摘A 2.05μm holmium-doped yttrium lithium fluoride(Ho:YLF)master oscillator power amplifier system with both high average power and high pulse energy operating at a 1 kHz repetition rate is demonstrated,achieving a maximum output power of 280 W with a pulse width of 14.5 ns.The system comprises three-stage amplifiers,boosting a 20 W seed laser to output powers of 110,205 and 280 W,corresponding to extraction efficiencies of 46.1%,45.0%and 34.9%,respectively.At maximum output,the system exhibits excellent beam quality(M_(x)^(2)=1.22 and M_(y)^(2)=1.23)and power stability(root mean square=0.5%over 30 min).To the best of our knowledge,this work reports the highest pulse energy(280 mJ)achieved for a 2μm laser operating at a kHz repetition rate.In addition,a slice model of an end-pumped quasi-three-level laser amplifier was developed to analyze the output limitations of multi-stage Ho:YLF amplifiers based on rod geometry,providing theoretical support for the experimental results.
基金This work has been partly supported by the German Federal Ministry of Education and Research(BMBF)under contract 13N12082‘NEXUS’,by the Thuringian Ministry of Education,Science and Culture(TMBWK)under contract 12037-515‘BURST’by the European Research Council under the ERC grant agreement no.[617173]‘ACOPS’+3 种基金by the Deutsche Forschungsgemeinschaft Cluster of Excellence‘Munich-Centre for Advanced Photonics’(munich-photonics.de).AK acknowledges financial support by the Helmholtz-Institute Jena.TE acknowledges financial support by the CarlZeiss-Stiftung.IP and SH acknowledge financial support by the BMBF under PhoNa-Photonische Nanomaterialien,contract number 03IS2101B.
文摘Since the advent of femtosecond lasers,performance improvements have constantly impacted on existing applications and enabled novel applications.However,one performance feature bearing the potential of a quantum leap for high-field applications is still not available:the simultaneous emission of extremely high peak and average powers.Emerging applications such as laser particle acceleration require exactly this performance regime and,therefore,challenge laser technology at large.On the one hand,canonical bulk systems can provide pulse peak powers in the multi-terawatt to petawatt range,while on the other hand,advanced solid-state-laser concepts such as the thin disk,slab or fibre are well known for their high efficiency and their ability to emit high average powers in the kilowatt range with excellent beam quality.In this contribution,a compact laser system capable of simultaneously providing high peak and average powers with high wall-plug efficiency is proposed and analysed.The concept is based on the temporal coherent combination(pulse stacking)of a pulse train emitted from a high-repetition-rate femtosecond laser system in a passive enhancement cavity.Thus,the pulse energy is increased at the cost of the repetition rate while almost preserving the average power.The concept relies on a fast switching element for dumping the enhanced pulse out of the cavity.The switch constitutes the key challenge of our proposal.Addressing this challenge could,for the first time,allow the highly efficient dumping of joule-class pulses at megawatt average power levels and lead to unprecedented laser parameters.
基金supported by the National Natural Science Foundation of China (NSFC) (No.12164030)Young Science and Technology Talents of Inner Mongolia (No.NJYT22101)Central Government Guides Local Science and Technology Development Fund (No.2023ZY0005)
文摘Mamyshev oscillators (MOs) exhibit the potential for generating high average power and ultrashort pulses. Herein,we construct an MO using flexible double-cladding ytterbium-fiber with a fusion-spliced-combiner pumped scheme.Consistent with the most reported research results, the offset filter separation significantly affects the pulse characteristics(spectrum, pulse duration, etc.). Notably, in comparison with red-shifting, blue-shifting the peak spectral emission of the grating filter relative to a constant central wavelength of the bandpass filter substantially enhances the laser output characteristics. This phenomenon, which has not been previously reported, results in an average power up to 2.23 W and a pulse duration as short as 49 fs. To our knowledge, this is the highest average power achieved in sub-50 fs pulse duration in the nonlinear polarization rotation-assisted mode-locked MO laser architecture. The presented technique offers unique scientific proof for developing ultrafast laser sources with higher average power and shorter pulse duration.
基金supported by the Technology Agency of the Czech Republic(TM03000045)co-funded by the European Union and the state budget of the Czech Republic under the project Las App(CZ.02.01.01/00/22_008/0004573)
文摘We present a study of second harmonic generation(SHG) and third harmonic generation(THG) in lithium triborate(LBO) crystals using a high-energy,10-J-class,10 Hz ytterbium-doped yttrium aluminum garnet laser system.We achieved high conversion efficiencies of 75% for SHG and 56% for THG for Gaussian-like temporal pulse shapes and top-hat-like beam profiles.The angular and temperature dependence of the LBO crystals was measured and validated through numerical simulations.The SHG process exhibited an angular acceptance bandwidth of 1.33 mrad and a temperature acceptance bandwidth of 2.61 K,while the THG process showed 1.19 mrad and 1.35 K,respectively.In addition,long-term stability measurements revealed root mean square energy stabilities of 1.3% for SHG and 1.24% for THG.These results showcase the reliability of LBO crystals for high-energy,high-average-power harmonic generation.The developed system offers automated switching between harmonics provided at the system output.The system can be easily adapted to neodymium-doped yttrium aluminum garnet based pump lasers as well.
