Fraction repetition(FR)codes are integral in distributed storage systems(DSS)with exact repair-by-transfer,while pliable fraction repetition codes are vital for DSSs in which both the per-node storage and repetition d...Fraction repetition(FR)codes are integral in distributed storage systems(DSS)with exact repair-by-transfer,while pliable fraction repetition codes are vital for DSSs in which both the per-node storage and repetition degree can easily be adjusted simultaneously.This paper introduces a new type of pliable FR codes,called absolute balanced pliable FR(ABPFR)codes,in which the access balancing in DSS is considered.Additionally,the equivalence between pliable FR codes and resolvable transversal packings in combinatorial design theory is presented.Then constructions of pliable FR codes and ABPFR codes based on resolvable transversal packings are presented.展开更多
Driving of the nuclear fusion reaction p+^(11)B3α+8.7 MeV under laboratory conditions by interaction between high-power laser pulses and matter has become a popular field of research,owing to its numerous potential a...Driving of the nuclear fusion reaction p+^(11)B3α+8.7 MeV under laboratory conditions by interaction between high-power laser pulses and matter has become a popular field of research,owing to its numerous potential applications:as an alternative to deuterium-tritium for fusion energy production,astrophysics studies,and alpha-particle generation for medical treatment.One possible scheme for laser-driven p-^(11)B reactions is to direct a beam of laser-accelerated protons onto a boron(B)sample(the so-called“pitcher-catcher”scheme).This technique has been successfully implemented on large high-energy lasers,yielding hundreds of joules per shot at low repetition.We present here a complementary approach,exploiting the high repetition rate of the VEGA III petawatt laser at CLPU(Spain),aiming at accumulating results from many interactions at much lower energy,to provide better control of the parameters and the statistics of the measurements.Despite a moderate energy per pulse,our experiment allowed exploration of the laser-driven fusion process with tens(up to hundreds)of laser shots.The experiment provided a clear signature of the reactions involved and of the fusion products,accumulated over many shots,leading to an improved optimization of the diagnostics for experimental campaigns of this type.In this paper,we discuss the effectiveness of laser-driven p-11B fusion in the pitcher-catcher scheme,at a high repetition rate,addressing the challenges of this experimental scheme and highlighting its critical aspects.Our proposed methodology allows evaluation of the performance of this scheme for laser-driven alpha particle production and can be adapted to high-repetition-rate laser facilities with higher energy and intensity.展开更多
We report on a Kerr-lens mode-locked(KLM)femtosecond Yb:CaYAlO_(4)(Yb:CYA)laser operating at a repetition rate of 1.04 GHz,pumped by a single-mode fiber laser.The laser delivers an average output power of 1.37 W with ...We report on a Kerr-lens mode-locked(KLM)femtosecond Yb:CaYAlO_(4)(Yb:CYA)laser operating at a repetition rate of 1.04 GHz,pumped by a single-mode fiber laser.The laser delivers an average output power of 1.37 W with a pulse duration of 109 fs.Potential improvements,including scaling the pump power,increasing the repetition rate,and further reducing the pulse duration,are discussed.This study contributes to the advancement of Watt-level GHz femtosecond laser generation and its applications.展开更多
The Shanghai high-repetition-rate X-ray free-electron laser and extreme light facility(SHINE)operates at a maximum repetition rate of 1 MHz.Kicker magnets are key components that distribute electron bunches into three...The Shanghai high-repetition-rate X-ray free-electron laser and extreme light facility(SHINE)operates at a maximum repetition rate of 1 MHz.Kicker magnets are key components that distribute electron bunches into three different undulator lines in a bunch-by-bunch mode.The kicker field width must be less than the time interval between bunches.A lumpedinductance kicker prototype was developed using a vacuum chamber with a single-turn coil.The full magnetic field strength was 0.005 T.This paper presents the requirements,design considerations,design parameters,magnetic field calculations,and measurements of the kicker magnets.The relevant experimental results are also presented.The pulse width of the magnetic field was approximately 600 ns,and the maximum operation repetition rate was 1 MHz.The developed kicker satisfies the requirements for the SHINE project.Finally,numerous recommendations for the future optimization of kicker magnets are provided.展开更多
Fiction and Repetition is and will remain a distinguished deconstructionist guide of literary criticism. However, after detailed and systematic research, I also find some shortcomings in this important academic work: ...Fiction and Repetition is and will remain a distinguished deconstructionist guide of literary criticism. However, after detailed and systematic research, I also find some shortcomings in this important academic work: Firstly, written in the metaphysical language, Fiction and Repetition can never succeed in escaping the logocentrism and binary opposition inherent in this language.Secondly, based on Saussure's argument on langue, the monograph's view of indeterminacy of literary work's meaning is theoretically correct but practically inadequate. Last but not the least, Miller's proposal on repetition also has some limitations. By taking into account both the work's merits and demerits, we can gain a more comprehensive outlook on Miller's idea of repetition as well as the deconstruction theory of literary criticism in general.展开更多
Satellite laser ranging （SLR） is one of the major space geodetic instruments, which has various applications in earth science. In this paper, we introduce several issues regarding the key technology implementation o...Satellite laser ranging （SLR） is one of the major space geodetic instruments, which has various applications in earth science. In this paper, we introduce several issues regarding the key technology implementation of high-repetition-rate SLR system. Compared with traditional technology, using kHz and 8ps pulse width laser component, the data quantity and quality of high-repetition-rate satellite laser ranging （SLR） can be significantly improved. The characteristics of high-repetition-rate laser ranging and the key technologies are presented, including the event timer with the precision of picosecond, the generation of range gate signal, and so on. All of them are based on the Field Programmable Gate Arrays （FPGA） and tested on China mobile SLR system-TROS1000. Finally, the observations of satellite Beacon-C are given.展开更多
Based on a theoretical model of Q-switched laser with the influences of the driving signal sent to the Pockels cell and the doping concentration of the gain medium taken into account,a method of achieving high energy ...Based on a theoretical model of Q-switched laser with the influences of the driving signal sent to the Pockels cell and the doping concentration of the gain medium taken into account,a method of achieving high energy sub-nanosecond Q-switched lasers is proposed and verified in experiment.When a Nd:YVO4 crystal with a doping concentration of 0.7 at.%is used as a gain medium and a driving signal with the optimal high-level voltage is applied to the Pockels cell,a stable single-transverse-mode electro-optical Q-switched laser with a pulse width of 0.77 ns and a pulse energy of 1.04 mJ operating at the pulse repetition frequency of 1 kHz is achieved.The precise tuning of the pulse width is also demonstrated.展开更多
A compact high power diode-pumped passively mode-locked Nd:YVO_4 laser with high repetition rate is realized.Using an Nd:YVO_4 crystal and a semiconductor saturable absorber mirror(SESAM) in the oscillator, the picose...A compact high power diode-pumped passively mode-locked Nd:YVO_4 laser with high repetition rate is realized.Using an Nd:YVO_4 crystal and a semiconductor saturable absorber mirror(SESAM) in the oscillator, the picosecond pulse output with an average power of 1.38 W, a repetition rate of 3.24 GHz, and a pulse duration of 11.4 ps is achieved. After one stage of amplification, the final output power reaches 11.34 W, corresponding to a total optical-to-optical efficiency of about 32%. The root mean square(RMS) value of power fluctuation is demonstrated to be less than 0.6% in 24 hours,showing a superior stability with the compact configuration.展开更多
The P3 installation of ELI-Beamlines is conceived as an experimental platform for multiple high-repetition-rate laser beams spanning time scales from femtosecond via picosecond to nanosecond.The upcoming L4n laser bea...The P3 installation of ELI-Beamlines is conceived as an experimental platform for multiple high-repetition-rate laser beams spanning time scales from femtosecond via picosecond to nanosecond.The upcoming L4n laser beamline will provide shaped nanosecond pulses of up to 1.9 kJ at a maximum repetition rate of 1 shot/min.This beamline will provide unique possibilities for high-pressure,high-energy-density physics,warm dense matter,and laser–plasma interaction experiments.Owing to the high repetition rate,it will become possible to obtain considerable improvements in data statistics,in particular,for equation-of-state data sets.The nanosecond beam will be coupled with short sub-picosecond pulses,providing high-resolution diagnostic tools by either irradiating a backlighter target or driving a betatron setup to generate energetic electrons and hard X-rays.展开更多
We report on a compact, stable, all-fiberized narrow-linewidth(0.045 nm) pulsed laser source emitting laser beam with a wavelength of 266 nm, and tunable pulse width and repetition rate. The system is based on all-fib...We report on a compact, stable, all-fiberized narrow-linewidth(0.045 nm) pulsed laser source emitting laser beam with a wavelength of 266 nm, and tunable pulse width and repetition rate. The system is based on all-fiberized nanosecond amplifier architecture, which consists of Yb-doped fiber preamplifiers and a super-large-mode-area Yb-doped fiber power amplifier. The fiber amplifier with a core of 50 μm is used to raise the threshold of the stimulated Brillouin scattering(SBS) effect and to obtain high output power and single pulse energy. Using lithium triborate(LBO) crystal and betabarium borate(BBO) crystal for realizing the second-harmonic generation(SHG) and fourth-harmonic generation(FHG),we achieve 17 μJ(1.73 W) and 0.66 μJ(66 mW), respectively, at wavelengths of 532 nm and 266 nm and a repetition rate of 100 kHz with pulse width of 4 ns. This source has great potential applications in fluorescence research and solar-blind ultraviolet optical communication.展开更多
We demonstrate a diode pumped Yb：LuVO4 laser that can be passively Q-switched by a Cr^（4＋）：YAG saturable absorber having an initial transmission as high as 99.3%.A maximum pulsed output power of 2.35 W is generat...We demonstrate a diode pumped Yb：LuVO4 laser that can be passively Q-switched by a Cr^（4＋）：YAG saturable absorber having an initial transmission as high as 99.3%.A maximum pulsed output power of 2.35 W is generated at a repetition rate of 285.7 kHz,approaching or very near the intrinsic upper limit imposed by the recovery time of the Cr^（4＋）：YAG saturable absorber,and the resulting pulse energy,duration and peak power are,respectively,8.2μJ,39.2ns and 0.209kW.展开更多
Application of continuous repetition of motor imagery can improve the performance of exercise tasks.However,there is a lack of more detailed neurophysiological evidence to support the formulation of clear standards fo...Application of continuous repetition of motor imagery can improve the performance of exercise tasks.However,there is a lack of more detailed neurophysiological evidence to support the formulation of clear standards for interventions using motor imagery.Moreover,identification of motor imagery intervention time is necessary because it exhibits possible central fatigue.Therefore,the purpose of this study was to elucidate the development of fatigue during continuous repetition of motor imagery through objective and subjective evaluation.The study involved two experiments.In experiment 1,14 healthy young volunteers were required to imagine grasping and lifting a 1.5-L plastic bottle using the whole hand.Each participant performed the motor imagery task 100 times under each condition with 48 hours interval between two conditions:500 mL or 1500 mL of water in the bottle during the demonstration phase.Mental fatigue and a decrease in pinch power appeared under the 1500-mL condition.There were changes in concentration ability or corticospinal excitability,as assessed by motor evoked potentials,between each set with continuous repetition of motor imagery also under the 1500-mL condition.Therefore,in experiment 2,12 healthy volunteers were required to perform the motor imagery task 200 times under the 1500-mL condition.Both concentration ability and corticospinal excitability decreased.This is the first study to show that continuous repetition of motor imagery can decrease corticospinal excitability in addition to producing mental fatigue.This study was approved by the Institutional Ethics Committee at the Nagasaki University Graduate School of Biomedical and Health Sciences(approval No.18121302)on January 30,2019.展开更多
In this paper,we address the Alamouti code in Filter-Bank Multicarrier with Offset Quadrature Amplitude Modulation(FBMC/OQAM)and propose a novel block-wise Alamouti code,in which a repeated block is designed to elimin...In this paper,we address the Alamouti code in Filter-Bank Multicarrier with Offset Quadrature Amplitude Modulation(FBMC/OQAM)and propose a novel block-wise Alamouti code,in which a repeated block is designed to eliminate the imaginary interference among FBMC/OQAM symbols.The proposed approach exhibits a higher spectral efficiency than the conventional block-wise Alamouti scheme,as only one column of zero symbols is used as a guard interval instead of two.Furthermore,compared to the conventional scheme,the bit error ratio is improved in the proposed block-wise Alamouti,as the assumption on channel invariance at two adjacent sub-carriers is not required.Simulation results indicate that,with a significantly reduced overhead,the proposed Alamouti scheme achieves better performance over the conventional block-wise Alamouti scheme.展开更多
We propose and demonstrate a Q-switched erbium-doped fiber laser （EDFL） using an erbium-doped zirconia-alumina silica glass-based fiber （Zr-EDF） as a saturable absorber. As a 16-cm-long Zr-EDF is incorporated into...We propose and demonstrate a Q-switched erbium-doped fiber laser （EDFL） using an erbium-doped zirconia-alumina silica glass-based fiber （Zr-EDF） as a saturable absorber. As a 16-cm-long Zr-EDF is incorporated into a ring EDFL cavity, a stable Q-switching pulse train operating at 1565？nm wavelength is successfully obtained. The repetition rate is tunable from 33.97？kHz to 71.23？kHz by increasing the pump power from the threshold of 26？mW to the maximum of 74？mW. The highest pulse energy of 26.67？nJ is obtained at the maximum pump power.展开更多
We demonstrate the generation of supercontinuum(SC) spectrum covering S+C+L band of optical communication by injecting 1.4 ps optical pulses with center wavelength of 1552 nm and repetition rate of 10 GHz into an all-...We demonstrate the generation of supercontinuum(SC) spectrum covering S+C+L band of optical communication by injecting 1.4 ps optical pulses with center wavelength of 1552 nm and repetition rate of 10 GHz into an all-normal dispersion photonic crystal fiber(PCF) with length of 80 m. The experimental results are in good agreement with the numerical simulations, which are used to illustrate the SC generation dynamics by self-phase modulation and optical wave breaking(WB).展开更多
Long-term ultra-precision synchronization between optical frequency combs(OFCs) and microwave oscillators is important for various fields, including scientific observation, smart grid, positioning and navigation, etc....Long-term ultra-precision synchronization between optical frequency combs(OFCs) and microwave oscillators is important for various fields, including scientific observation, smart grid, positioning and navigation, etc. Here, a phase-locked loop system based on fiber loop optical-microwave phase detector(FLOM-PD) is proposed to realize the synchronization of the repetition rate of OFCs and rubidium atomic clocks. Firstly, the scheme and locking process of the system are elaborated, then the mathematical model of the system is established, and the feasibility of the scheme is proved by theoretical analysis and experimental verification. After synchronization, the instability of the system reaches 8.69×10^(-12)at 1 s and 2.94×10^(-13)at 1 000 s, indicating that the phase synchronization system can achieve ultra-precision and stability of OFCs repetition rate.展开更多
Advances in X-ray laser sources have paved the way to relativistic attosecond X-ray laser pulses and opened up the possibility of exploring highenergy-density physics with this technology.With particle-in-cell simulat...Advances in X-ray laser sources have paved the way to relativistic attosecond X-ray laser pulses and opened up the possibility of exploring highenergy-density physics with this technology.With particle-in-cell simulations,we investigate the interaction of realistic metal crystals with relativistic X-ray laser pulses of parameters that will be available in the near future.A wakefield of the order of TV/cm is excited in the crystal and accelerates trapped electrons stably even though the wakefield is locally modulated by the crystal lattice.Electron injection either occurs at the sharp crystal-vacuum boundary or is controlled by coating the crystal with a high-density film.High-repetition-rate attosecond(20 as)monoenergetic electron beams of energy 125 MeV,charge 100 fC,and emittance 1.6310−9mrad can be produced by shining MHz X-ray laser pulses of energy 2.1 mJ onto coated crystals several micrometers thick.Such a miniature crystal accelerator,which has high reproducibility and allows sufficient control of the parameters of the electron beams,greatly expands the applications of X-ray free electron lasers.For example,it could serve as an ideal electron source for ultrafast electron diffraction and ultrafast electron microscopy to achieve attosecond resolution.展开更多
Laser processing with high-power ultrashort pulses,which promises high precision and efficiency,is an emerging new tool for material structuring.High repetition rate ultrafast laser highlighting with a higher degree o...Laser processing with high-power ultrashort pulses,which promises high precision and efficiency,is an emerging new tool for material structuring.High repetition rate ultrafast laser highlighting with a higher degree of freedom in its burst mode is believed to be able to create micro/nanostructures with even more variety,which is promising for electrochemical applications.We employ a homemade high repetition rate ultrafast fiber laser for structuring metal nickel(Ni)and thus preparing electrocatalysts for hydrogen evolution reaction(HER)for the first time,we believe.Different processing parameters are designed to create three groups of samples with different micro/nanostructures.The various micro/nanostructures not only increase the surface area of the Ni electrode but also regulate local electric field and help discharge hydrogen bubbles,which offer more favorable conditions for HER.All groups of the laser-structured Ni exhibit enhanced electrocatalytic activity for HER in the alkaline solution.Electrochemical measurements demonstrate that the overpotential at 10 mAcm−2 can be decreased as much as 182 mV compared with the overpotential of the untreated Ni(−457 mV versus RHE).展开更多
Ultrashort pulses at 920 nm are a highly desired light source in two-photon microscopy for the efficient excitation of green fluorescence protein.Although Nd3þ-doped fibers have been utilized for 920-nm ultrashor...Ultrashort pulses at 920 nm are a highly desired light source in two-photon microscopy for the efficient excitation of green fluorescence protein.Although Nd3þ-doped fibers have been utilized for 920-nm ultrashort pulse generation,the competitive amplified spontaneous emission(ASE)at 1.06μm remains a significant challenge in improving their performance.Here,we demonstrate a coordination engineering strategy to tailor the properties of Nd3þ-doped silica glass and fiber.By elevating the covalency between Nd3þand bonded anions via sulfur incorporation,the fiber gain performance at 920 nm is enhanced,and 1.06-μm ASE intensity is suppressed simultaneously.As a result,the continuous-wave laser efficiencies and signal-to-noise ratio at 920 nm by this fiber are significantly enhanced.Importantly,the stable picosecond pulses at 920 nm are produced by a passive mode-locking technique with a fundamental repetition rate up to 207 MHz,which,to the best of our knowledge,is the highest reported repetition rate realized by Nd3þ-doped silica fibers.The presented strategy enriches the capacity of Nd3þ-doped silica fiber in generating 920-nm ultrashort pulses for application in biophotonics,and it also provides a promising way to tune the properties of rare-earth ion-doped silica glasses and fibers toward ultrafast lasers.展开更多
基金Supported in part by the National Key R&D Program of China(No.2020YFA0712300)NSFC(No.61872353)。
文摘Fraction repetition(FR)codes are integral in distributed storage systems(DSS)with exact repair-by-transfer,while pliable fraction repetition codes are vital for DSSs in which both the per-node storage and repetition degree can easily be adjusted simultaneously.This paper introduces a new type of pliable FR codes,called absolute balanced pliable FR(ABPFR)codes,in which the access balancing in DSS is considered.Additionally,the equivalence between pliable FR codes and resolvable transversal packings in combinatorial design theory is presented.Then constructions of pliable FR codes and ABPFR codes based on resolvable transversal packings are presented.
基金funded by the European Union via the Euratom Research and Training Program(Grant Agreement No.101052200-EUROfusion)funding from LASERLAB-EUROPE(Grant Agreement No.871124,European Union’s Horizon 2020 Research and Innovation Program)+5 种基金supported in part by the United States Department of Energy under Grant No.DE-FG02-93ER40773We also acknowledge support from Grant No.PID2021-125389OA-I00 funded by MCIN/AEI/10.13039/501100011033/FEDER,UEby“ERDF A Way of Making Europe”by the European Union and Unidad de Investigación Consolidada of Junta de Castilla y León UIC 167supported in part by the National Natural Science Foundation of China under Grant No.12375125the Fundamental Research Funds for the Central Universitiesthe support of the Czech Science Foundation through Grant No.GACR24-11398S.
文摘Driving of the nuclear fusion reaction p+^(11)B3α+8.7 MeV under laboratory conditions by interaction between high-power laser pulses and matter has become a popular field of research,owing to its numerous potential applications:as an alternative to deuterium-tritium for fusion energy production,astrophysics studies,and alpha-particle generation for medical treatment.One possible scheme for laser-driven p-^(11)B reactions is to direct a beam of laser-accelerated protons onto a boron(B)sample(the so-called“pitcher-catcher”scheme).This technique has been successfully implemented on large high-energy lasers,yielding hundreds of joules per shot at low repetition.We present here a complementary approach,exploiting the high repetition rate of the VEGA III petawatt laser at CLPU(Spain),aiming at accumulating results from many interactions at much lower energy,to provide better control of the parameters and the statistics of the measurements.Despite a moderate energy per pulse,our experiment allowed exploration of the laser-driven fusion process with tens(up to hundreds)of laser shots.The experiment provided a clear signature of the reactions involved and of the fusion products,accumulated over many shots,leading to an improved optimization of the diagnostics for experimental campaigns of this type.In this paper,we discuss the effectiveness of laser-driven p-11B fusion in the pitcher-catcher scheme,at a high repetition rate,addressing the challenges of this experimental scheme and highlighting its critical aspects.Our proposed methodology allows evaluation of the performance of this scheme for laser-driven alpha particle production and can be adapted to high-repetition-rate laser facilities with higher energy and intensity.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFB4600158)。
文摘We report on a Kerr-lens mode-locked(KLM)femtosecond Yb:CaYAlO_(4)(Yb:CYA)laser operating at a repetition rate of 1.04 GHz,pumped by a single-mode fiber laser.The laser delivers an average output power of 1.37 W with a pulse duration of 109 fs.Potential improvements,including scaling the pump power,increasing the repetition rate,and further reducing the pulse duration,are discussed.This study contributes to the advancement of Watt-level GHz femtosecond laser generation and its applications.
基金This work was supported by the Shanghai Municipal Science and Technology Major Project(No.2017SHZDZX02)the National Natural Science Foundation of China(No.12005282)+1 种基金the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2021283)the Shanghai Pilot Program for Basic Research—Chinese Academy of Science,Shanghai Branch(JCYJSHFY-2021-010).
文摘The Shanghai high-repetition-rate X-ray free-electron laser and extreme light facility(SHINE)operates at a maximum repetition rate of 1 MHz.Kicker magnets are key components that distribute electron bunches into three different undulator lines in a bunch-by-bunch mode.The kicker field width must be less than the time interval between bunches.A lumpedinductance kicker prototype was developed using a vacuum chamber with a single-turn coil.The full magnetic field strength was 0.005 T.This paper presents the requirements,design considerations,design parameters,magnetic field calculations,and measurements of the kicker magnets.The relevant experimental results are also presented.The pulse width of the magnetic field was approximately 600 ns,and the maximum operation repetition rate was 1 MHz.The developed kicker satisfies the requirements for the SHINE project.Finally,numerous recommendations for the future optimization of kicker magnets are provided.
文摘Fiction and Repetition is and will remain a distinguished deconstructionist guide of literary criticism. However, after detailed and systematic research, I also find some shortcomings in this important academic work: Firstly, written in the metaphysical language, Fiction and Repetition can never succeed in escaping the logocentrism and binary opposition inherent in this language.Secondly, based on Saussure's argument on langue, the monograph's view of indeterminacy of literary work's meaning is theoretically correct but practically inadequate. Last but not the least, Miller's proposal on repetition also has some limitations. By taking into account both the work's merits and demerits, we can gain a more comprehensive outlook on Miller's idea of repetition as well as the deconstruction theory of literary criticism in general.
基金supported by the National Natural Science Foundation of China(40774013)
文摘Satellite laser ranging （SLR） is one of the major space geodetic instruments, which has various applications in earth science. In this paper, we introduce several issues regarding the key technology implementation of high-repetition-rate SLR system. Compared with traditional technology, using kHz and 8ps pulse width laser component, the data quantity and quality of high-repetition-rate satellite laser ranging （SLR） can be significantly improved. The characteristics of high-repetition-rate laser ranging and the key technologies are presented, including the event timer with the precision of picosecond, the generation of range gate signal, and so on. All of them are based on the Field Programmable Gate Arrays （FPGA） and tested on China mobile SLR system-TROS1000. Finally, the observations of satellite Beacon-C are given.
基金the National Key Research and Development Program of China(Grant No.2017YFB0405203)the Shanxi“1331 Project”Key Subjects Construction,China(Grant No.1331KSC).
文摘Based on a theoretical model of Q-switched laser with the influences of the driving signal sent to the Pockels cell and the doping concentration of the gain medium taken into account,a method of achieving high energy sub-nanosecond Q-switched lasers is proposed and verified in experiment.When a Nd:YVO4 crystal with a doping concentration of 0.7 at.%is used as a gain medium and a driving signal with the optimal high-level voltage is applied to the Pockels cell,a stable single-transverse-mode electro-optical Q-switched laser with a pulse width of 0.77 ns and a pulse energy of 1.04 mJ operating at the pulse repetition frequency of 1 kHz is achieved.The precise tuning of the pulse width is also demonstrated.
基金Project supported by the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB16030200)the National Natural Science Foundation of China(Grant Nos.11774410 and 61575217)+1 种基金the National Key Scientific Instruments Development Program of China(Grant No.2012YQ120047)the Key Research Program of Frontier Sciences of Chinese Academy of Sciences(Grant No.KJZD-EW-L11-03)
文摘A compact high power diode-pumped passively mode-locked Nd:YVO_4 laser with high repetition rate is realized.Using an Nd:YVO_4 crystal and a semiconductor saturable absorber mirror(SESAM) in the oscillator, the picosecond pulse output with an average power of 1.38 W, a repetition rate of 3.24 GHz, and a pulse duration of 11.4 ps is achieved. After one stage of amplification, the final output power reaches 11.34 W, corresponding to a total optical-to-optical efficiency of about 32%. The root mean square(RMS) value of power fluctuation is demonstrated to be less than 0.6% in 24 hours,showing a superior stability with the compact configuration.
基金The authors acknowledge support from the projects“Advanced Research Using High Intensity Laser Produced Photons and Particles(ADONIS)”(Grant No.CZ.02.1.01/0.0/0.0/16_019/0000789)“High Field Initiative(HiFI)”(Grant No.CZ.02.1.01/0.0/0.0/15_003/0000449)both from the European Regional Development Fund.The results of the Project LQ1606 were obtained with financial support from the Ministry of Education,Youth and Sports as part of targeted support from the National Program of Sustainability II.
文摘The P3 installation of ELI-Beamlines is conceived as an experimental platform for multiple high-repetition-rate laser beams spanning time scales from femtosecond via picosecond to nanosecond.The upcoming L4n laser beamline will provide shaped nanosecond pulses of up to 1.9 kJ at a maximum repetition rate of 1 shot/min.This beamline will provide unique possibilities for high-pressure,high-energy-density physics,warm dense matter,and laser–plasma interaction experiments.Owing to the high repetition rate,it will become possible to obtain considerable improvements in data statistics,in particular,for equation-of-state data sets.The nanosecond beam will be coupled with short sub-picosecond pulses,providing high-resolution diagnostic tools by either irradiating a backlighter target or driving a betatron setup to generate energetic electrons and hard X-rays.
基金Project supported by the Key Program of Beijing Municipal Natural Science Foundation, China (Grant No. KZ201910005006)the National Nature Science Foundation of China (Grant No. 62005004)+1 种基金the Natural Science Foundation of Beijing Municipality, China (Grant No. 4204091)the National Science Foundation for Postdoctor Scientists of China (Grant No. 212423)。
文摘We report on a compact, stable, all-fiberized narrow-linewidth(0.045 nm) pulsed laser source emitting laser beam with a wavelength of 266 nm, and tunable pulse width and repetition rate. The system is based on all-fiberized nanosecond amplifier architecture, which consists of Yb-doped fiber preamplifiers and a super-large-mode-area Yb-doped fiber power amplifier. The fiber amplifier with a core of 50 μm is used to raise the threshold of the stimulated Brillouin scattering(SBS) effect and to obtain high output power and single pulse energy. Using lithium triborate(LBO) crystal and betabarium borate(BBO) crystal for realizing the second-harmonic generation(SHG) and fourth-harmonic generation(FHG),we achieve 17 μJ(1.73 W) and 0.66 μJ(66 mW), respectively, at wavelengths of 532 nm and 266 nm and a repetition rate of 100 kHz with pulse width of 4 ns. This source has great potential applications in fluorescence research and solar-blind ultraviolet optical communication.
基金Supported by the National Natural Science Foundation of China under Grant No 11574170
文摘We demonstrate a diode pumped Yb：LuVO4 laser that can be passively Q-switched by a Cr^（4＋）：YAG saturable absorber having an initial transmission as high as 99.3%.A maximum pulsed output power of 2.35 W is generated at a repetition rate of 285.7 kHz,approaching or very near the intrinsic upper limit imposed by the recovery time of the Cr^（4＋）：YAG saturable absorber,and the resulting pulse energy,duration and peak power are,respectively,8.2μJ,39.2ns and 0.209kW.
文摘Application of continuous repetition of motor imagery can improve the performance of exercise tasks.However,there is a lack of more detailed neurophysiological evidence to support the formulation of clear standards for interventions using motor imagery.Moreover,identification of motor imagery intervention time is necessary because it exhibits possible central fatigue.Therefore,the purpose of this study was to elucidate the development of fatigue during continuous repetition of motor imagery through objective and subjective evaluation.The study involved two experiments.In experiment 1,14 healthy young volunteers were required to imagine grasping and lifting a 1.5-L plastic bottle using the whole hand.Each participant performed the motor imagery task 100 times under each condition with 48 hours interval between two conditions:500 mL or 1500 mL of water in the bottle during the demonstration phase.Mental fatigue and a decrease in pinch power appeared under the 1500-mL condition.There were changes in concentration ability or corticospinal excitability,as assessed by motor evoked potentials,between each set with continuous repetition of motor imagery also under the 1500-mL condition.Therefore,in experiment 2,12 healthy volunteers were required to perform the motor imagery task 200 times under the 1500-mL condition.Both concentration ability and corticospinal excitability decreased.This is the first study to show that continuous repetition of motor imagery can decrease corticospinal excitability in addition to producing mental fatigue.This study was approved by the Institutional Ethics Committee at the Nagasaki University Graduate School of Biomedical and Health Sciences(approval No.18121302)on January 30,2019.
基金supported in part by the National Natural Science Foundation of China with Grant numbers 62001333,61729101,61831013 and 11804256.
文摘In this paper,we address the Alamouti code in Filter-Bank Multicarrier with Offset Quadrature Amplitude Modulation(FBMC/OQAM)and propose a novel block-wise Alamouti code,in which a repeated block is designed to eliminate the imaginary interference among FBMC/OQAM symbols.The proposed approach exhibits a higher spectral efficiency than the conventional block-wise Alamouti scheme,as only one column of zero symbols is used as a guard interval instead of two.Furthermore,compared to the conventional scheme,the bit error ratio is improved in the proposed block-wise Alamouti,as the assumption on channel invariance at two adjacent sub-carriers is not required.Simulation results indicate that,with a significantly reduced overhead,the proposed Alamouti scheme achieves better performance over the conventional block-wise Alamouti scheme.
基金Supported by the Postgraduate Research of Malaysia under Grant No PG098-2014Bthe CSIR of Government of India
文摘We propose and demonstrate a Q-switched erbium-doped fiber laser （EDFL） using an erbium-doped zirconia-alumina silica glass-based fiber （Zr-EDF） as a saturable absorber. As a 16-cm-long Zr-EDF is incorporated into a ring EDFL cavity, a stable Q-switching pulse train operating at 1565？nm wavelength is successfully obtained. The repetition rate is tunable from 33.97？kHz to 71.23？kHz by increasing the pump power from the threshold of 26？mW to the maximum of 74？mW. The highest pulse energy of 26.67？nJ is obtained at the maximum pump power.
基金supported by the Guangdong Science and Technology Program(No.2012B090600009)the Guangdong Natural Science Fund(No.10451170003004948)
文摘We demonstrate the generation of supercontinuum(SC) spectrum covering S+C+L band of optical communication by injecting 1.4 ps optical pulses with center wavelength of 1552 nm and repetition rate of 10 GHz into an all-normal dispersion photonic crystal fiber(PCF) with length of 80 m. The experimental results are in good agreement with the numerical simulations, which are used to illustrate the SC generation dynamics by self-phase modulation and optical wave breaking(WB).
基金supported by the National Natural Science Foundation of China(No.U2031208)。
文摘Long-term ultra-precision synchronization between optical frequency combs(OFCs) and microwave oscillators is important for various fields, including scientific observation, smart grid, positioning and navigation, etc. Here, a phase-locked loop system based on fiber loop optical-microwave phase detector(FLOM-PD) is proposed to realize the synchronization of the repetition rate of OFCs and rubidium atomic clocks. Firstly, the scheme and locking process of the system are elaborated, then the mathematical model of the system is established, and the feasibility of the scheme is proved by theoretical analysis and experimental verification. After synchronization, the instability of the system reaches 8.69×10^(-12)at 1 s and 2.94×10^(-13)at 1 000 s, indicating that the phase synchronization system can achieve ultra-precision and stability of OFCs repetition rate.
基金This work was supported by the Ministry of Science and Technology of the People’s Republic of China(Grant Nos.2018YFA0404803 and 2016YFA0401102)the National Science Foundation of China(Grant No.11935008).
文摘Advances in X-ray laser sources have paved the way to relativistic attosecond X-ray laser pulses and opened up the possibility of exploring highenergy-density physics with this technology.With particle-in-cell simulations,we investigate the interaction of realistic metal crystals with relativistic X-ray laser pulses of parameters that will be available in the near future.A wakefield of the order of TV/cm is excited in the crystal and accelerates trapped electrons stably even though the wakefield is locally modulated by the crystal lattice.Electron injection either occurs at the sharp crystal-vacuum boundary or is controlled by coating the crystal with a high-density film.High-repetition-rate attosecond(20 as)monoenergetic electron beams of energy 125 MeV,charge 100 fC,and emittance 1.6310−9mrad can be produced by shining MHz X-ray laser pulses of energy 2.1 mJ onto coated crystals several micrometers thick.Such a miniature crystal accelerator,which has high reproducibility and allows sufficient control of the parameters of the electron beams,greatly expands the applications of X-ray free electron lasers.For example,it could serve as an ideal electron source for ultrafast electron diffraction and ultrafast electron microscopy to achieve attosecond resolution.
基金supported by the National Natural Science Foundation of China(Grant Nos.62375087,12374304,and 62235014)the NSFC Development of National Major Scientific Research Instrument(Grant No.61927816)+3 种基金the Mobility Programme of the Sino-German(Grant No.M-0296)the Introduced Innovative Team Project of Guangdong Pearl River Talents Program(Grant No.2021ZT09Z109)the Natural Science Foundation of Guangdong Province(Grant No.2021B1515020074)the Science and Technology Project of Guangdong(Grant No.2020B1212060002).
文摘Laser processing with high-power ultrashort pulses,which promises high precision and efficiency,is an emerging new tool for material structuring.High repetition rate ultrafast laser highlighting with a higher degree of freedom in its burst mode is believed to be able to create micro/nanostructures with even more variety,which is promising for electrochemical applications.We employ a homemade high repetition rate ultrafast fiber laser for structuring metal nickel(Ni)and thus preparing electrocatalysts for hydrogen evolution reaction(HER)for the first time,we believe.Different processing parameters are designed to create three groups of samples with different micro/nanostructures.The various micro/nanostructures not only increase the surface area of the Ni electrode but also regulate local electric field and help discharge hydrogen bubbles,which offer more favorable conditions for HER.All groups of the laser-structured Ni exhibit enhanced electrocatalytic activity for HER in the alkaline solution.Electrochemical measurements demonstrate that the overpotential at 10 mAcm−2 can be decreased as much as 182 mV compared with the overpotential of the untreated Ni(−457 mV versus RHE).
基金supported by the International Partnership Program of Chinese Academy of Sciences(Grant No.20XH1217)the National Natural Science Foundation of China(Grant Nos.61975216 and 62205356)the STCSM(Grant No.SKLSFO2022-02)。
文摘Ultrashort pulses at 920 nm are a highly desired light source in two-photon microscopy for the efficient excitation of green fluorescence protein.Although Nd3þ-doped fibers have been utilized for 920-nm ultrashort pulse generation,the competitive amplified spontaneous emission(ASE)at 1.06μm remains a significant challenge in improving their performance.Here,we demonstrate a coordination engineering strategy to tailor the properties of Nd3þ-doped silica glass and fiber.By elevating the covalency between Nd3þand bonded anions via sulfur incorporation,the fiber gain performance at 920 nm is enhanced,and 1.06-μm ASE intensity is suppressed simultaneously.As a result,the continuous-wave laser efficiencies and signal-to-noise ratio at 920 nm by this fiber are significantly enhanced.Importantly,the stable picosecond pulses at 920 nm are produced by a passive mode-locking technique with a fundamental repetition rate up to 207 MHz,which,to the best of our knowledge,is the highest reported repetition rate realized by Nd3þ-doped silica fibers.The presented strategy enriches the capacity of Nd3þ-doped silica fiber in generating 920-nm ultrashort pulses for application in biophotonics,and it also provides a promising way to tune the properties of rare-earth ion-doped silica glasses and fibers toward ultrafast lasers.
