In this research,we report the latest progress in the suppression of nanosecond prepulses from regenerative amplifier and multipass amplifiers in the SULF-1PW laser.The prepulse generated from the Pockels cell(PC)in a...In this research,we report the latest progress in the suppression of nanosecond prepulses from regenerative amplifier and multipass amplifiers in the SULF-1PW laser.The prepulse generated from the Pockels cell(PC)in a regenerative amplifier is delay-shifted by enlarging the distance between the PC and the nearby cavity mirror,and then removed by the extra pulse pickers outside the regenerative amplifier.The prepulses arising from multipass amplifiers are also further suppressed by adopting a novel amplifier configuration and properly rotating the Ti:sapphire crystals.After the optimizations,the temporal contrast on a nanosecond time scale is promoted to be better than a contrast level of 10^(-9).This research can provide beneficial guidance for the suppression of nanosecond prepulses in the high-peak-power femtosecond laser systems.展开更多
We theoretically study the nonlinear compression of a 20-rnJ, 1030-nm picosecond chirped pulse from the thin-disk amplifier in a krypton gas-filled hollow-core fiber. The chirp from the thin-disk amplifier system has ...We theoretically study the nonlinear compression of a 20-rnJ, 1030-nm picosecond chirped pulse from the thin-disk amplifier in a krypton gas-filled hollow-core fiber. The chirp from the thin-disk amplifier system has little influence on the initial pulse, however, it shows an effect on the nonlinear compression in hollow-core fiber. We use a large diameter hollow waveguide to restrict undesirable nonlinear effects such as ionization; on the other hand, we employ suitable gas pressure and fiber length to promise enough spectral broadening; with 600-μm, 6-bar （1 bar = 105 Pa）, 1.8-m hollow fiber, we obtain 31.5-fs pulse. Moreover, we calculate and discuss the optimal fiber lengths and gas pressures with different initial durations induced by different grating compression angles for reaching a given bandwidth. These results are meaningful for a compression scheme from picoseconds to femtoseconds.展开更多
Beam quality degradation during the transition from a laser wakefield accelerator to the vacuum is one of the reasons that cause the beam transport distortion, which hinders the way to compact free-electron-lasers. He...Beam quality degradation during the transition from a laser wakefield accelerator to the vacuum is one of the reasons that cause the beam transport distortion, which hinders the way to compact free-electron-lasers. Here,we performed transition simulation to initialize the beam parameters for beam optics transport. This initialization was crucial in matching the experimental results and the designed evolution of the beamline. We experimentally characterized properties of high-quality laser-wakefield-accelerated electron beams, such as transverse beam profile, divergence, and directionality after long-distance transport. By installing magnetic quadrupole lenses with tailored strength gradients, we successfully collimated the electron beams with tunable energies from 200 to 600 MeV.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 underlying mechanism of the spectral cleaning effect of the cross-polarized wave（XPW） generation process was theoretically investigated. This study shows that the spectral noise of an input spectrum can be remov...The underlying mechanism of the spectral cleaning effect of the cross-polarized wave（XPW） generation process was theoretically investigated. This study shows that the spectral noise of an input spectrum can be removed in the XPW generation process and that the spectral cleaning effect depends on the characteristics of the input pulses, such as the chirp and Fourier-transform-limited duration of the initial pulse, and the modulation amplitude and frequency of the spectral noise. Though these factors codetermine the output spectrum of the XPW generation process, the spectral cleaning effect is mainly affected by the initial pulse chirp. The smoothing of the spectrum in the XPW generation process leads to a significant enhancement of the coherent contrast.展开更多
The spatial chirp generated in the Ti：sapphire multipass amplifier is numerically investigated based on the one- dimensional （1D） and two-dimensional （2D） Frantz-Nodvik equations. The simulation indicates that th...The spatial chirp generated in the Ti：sapphire multipass amplifier is numerically investigated based on the one- dimensional （1D） and two-dimensional （2D） Frantz-Nodvik equations. The simulation indicates that the spatial chirp is induced by the spatially inhomogeneous gain, and it can be almost eliminated by utilization of proper beam profiles and spot sizes of the signal and pump pulses, for example, the pump pulse has a top-hatted beam profile and the signal pulse has a super-Gaussian beam profile with a relatively larger spot size. In this way, a clear understanding of spatial chirp mechanisms in the Ti：sapphire multipass amplifier is proposed, therefore we can effectively almost eliminate the spatial chirp and improve the beam quality of a high-power Ti：sapphire chirped pulse amplifier system.展开更多
基金This work was supported by the National Key R&D Program of China(Nos.2017YFE0123700 and 2022YFA1604401)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB1603)+2 种基金the National Natural Science Foundation of China(Nos.61925507 and 62375273)the Program of Shanghai Academic/Technology Research Leader(No.18XD1404200)the Shanghai Municipal Science and Technology Major Project(No.2017SHZDZX02).
文摘In this research,we report the latest progress in the suppression of nanosecond prepulses from regenerative amplifier and multipass amplifiers in the SULF-1PW laser.The prepulse generated from the Pockels cell(PC)in a regenerative amplifier is delay-shifted by enlarging the distance between the PC and the nearby cavity mirror,and then removed by the extra pulse pickers outside the regenerative amplifier.The prepulses arising from multipass amplifiers are also further suppressed by adopting a novel amplifier configuration and properly rotating the Ti:sapphire crystals.After the optimizations,the temporal contrast on a nanosecond time scale is promoted to be better than a contrast level of 10^(-9).This research can provide beneficial guidance for the suppression of nanosecond prepulses in the high-peak-power femtosecond laser systems.
基金Project supported by the National Basic Research Program of China(Grant No.2011CB808101)the Funds from the Chinese Academy of Sciences,and the National Natural Science Foundation of China(Grant Nos.11127901,10734080,61221064,60908008,and 61078037)
文摘We theoretically study the nonlinear compression of a 20-rnJ, 1030-nm picosecond chirped pulse from the thin-disk amplifier in a krypton gas-filled hollow-core fiber. The chirp from the thin-disk amplifier system has little influence on the initial pulse, however, it shows an effect on the nonlinear compression in hollow-core fiber. We use a large diameter hollow waveguide to restrict undesirable nonlinear effects such as ionization; on the other hand, we employ suitable gas pressure and fiber length to promise enough spectral broadening; with 600-μm, 6-bar （1 bar = 105 Pa）, 1.8-m hollow fiber, we obtain 31.5-fs pulse. Moreover, we calculate and discuss the optimal fiber lengths and gas pressures with different initial durations induced by different grating compression angles for reaching a given bandwidth. These results are meaningful for a compression scheme from picoseconds to femtoseconds.
基金supported by the National Natural Science Foundation of China(Nos.11127901,11425418,61521093,11304271,11205228,and 11505263)the Strategic Priority Research Program(B)(No.XDB16)+1 种基金the Youth Innovation Promotion Association CASthe State Key Laboratory Program of the Chinese Ministry of Science and Technology
文摘Beam quality degradation during the transition from a laser wakefield accelerator to the vacuum is one of the reasons that cause the beam transport distortion, which hinders the way to compact free-electron-lasers. Here,we performed transition simulation to initialize the beam parameters for beam optics transport. This initialization was crucial in matching the experimental results and the designed evolution of the beamline. We experimentally characterized properties of high-quality laser-wakefield-accelerated electron beams, such as transverse beam profile, divergence, and directionality after long-distance transport. By installing magnetic quadrupole lenses with tailored strength gradients, we successfully collimated the electron beams with tunable energies from 200 to 600 MeV.
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Project supported by the National Natural Science Foundation of China(Grant Nos.11127901,61521093,and 61505234)the International S&T Cooperation of Program of China(Grant No.2016YFE0119300)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB160301)the Youth Innovation Promotion Association,Chinese Academy of Sciences
文摘The underlying mechanism of the spectral cleaning effect of the cross-polarized wave（XPW） generation process was theoretically investigated. This study shows that the spectral noise of an input spectrum can be removed in the XPW generation process and that the spectral cleaning effect depends on the characteristics of the input pulses, such as the chirp and Fourier-transform-limited duration of the initial pulse, and the modulation amplitude and frequency of the spectral noise. Though these factors codetermine the output spectrum of the XPW generation process, the spectral cleaning effect is mainly affected by the initial pulse chirp. The smoothing of the spectrum in the XPW generation process leads to a significant enhancement of the coherent contrast.
基金Project supported by 100 Talents Program of Chinese Academy of Sciencesthe National Natural Science Foundation of China(Grant Nos.61475169,61521093,and 11127901)the Youth Innovation Promotion Association of Chinese Academy of Sciences
文摘The spatial chirp generated in the Ti：sapphire multipass amplifier is numerically investigated based on the one- dimensional （1D） and two-dimensional （2D） Frantz-Nodvik equations. The simulation indicates that the spatial chirp is induced by the spatially inhomogeneous gain, and it can be almost eliminated by utilization of proper beam profiles and spot sizes of the signal and pump pulses, for example, the pump pulse has a top-hatted beam profile and the signal pulse has a super-Gaussian beam profile with a relatively larger spot size. In this way, a clear understanding of spatial chirp mechanisms in the Ti：sapphire multipass amplifier is proposed, therefore we can effectively almost eliminate the spatial chirp and improve the beam quality of a high-power Ti：sapphire chirped pulse amplifier system.
