【摘要】 超强超快激光在强电磁场条件下探索极端物质状态的研究中，正发挥着日益重要的作用。研究人员在维持激光高峰值功率的同时，对其平均功率也提出了更高要求。北京激光加速创新中心（BLAIC）自主研发了一款拍瓦（PW）级激光装置，该装置采用啁啾脉冲放大（CPA）技术，以掺钛蓝宝石（Ti∶sapphire）晶体作为终端放大介质，具备双前端、双输出与高重复频率的特点。PW系统基于交叉偏振波产生（XPW）前端，目前已实现重复频率为1 Hz、脉冲宽度为26.4 fs、峰值功率为224.7 TW的脉冲激光输出；在此基础上，实现了宽谱激光放大，不仅保持了1 Hz的重复频率，单脉冲能量达48.7 J且600发次能量波动低至0.9%，还在大气环境中将脉冲宽度压缩至28.4 fs。数据分析结果表明，BLAIC-1 PW激光系统可稳定支持重复频率为1 Hz、峰值功率为1.2 PW的fs级激光输出。更多还原

【Abstract】 Significance Petawatt (PW,10¹⁵ W) femtosecond (fs,10^-15 s) lasers represent major breakthrough in creating extreme physical conditions in laboratory environments.Their core significance lies in advancing high-field physics and ultrafast process detection to unprecedented levels.In high-field physics,the extremely high intensity (≥10²² W/cm²) enables the generation of relativistic light intensities,driving electrons to a near-light speed and thereby opening new research avenues in relativistic optics.These lasers serve as critical tools for investigating laser nuclear physics and laboratory astrophysics （such as simulating supernova shocks and gamma-ray burst environments）,and realizing novel laser-driven particle （electrons,protons,ions） accelerators.In ultrafast science,femtosecond pulses make these lasers an ultimate probe for detecting ultrafast dynamics at atomic and molecular scales.More importantly,through high-harmonic generation,they have become the primary pump source for generating attosecond (10^-18 s) pulses,thus unlocking the realm of attosecond science.This capability makes it possible to directly observe and even manipulate the fundamental motion of electrons around atomic nuclei.Furthermore,they play a potentially crucial role in the“fast ignition”scheme for laser-driven inertial confinement fusion,offering a prospective pathway toward future clean energies.Therefore,petawatt femtosecond lasers constitute an indispensable strategic platform for both frontier fundamental scientific exploration and transformative technological development.Progress Since 2015,the Laser Plasma Laboratory at Peking University has conducted experimental research utilizing ultra-intense ultrafast lasers （200 TW/30 fs）,with a focus on particle acceleration,high-harmonic generation,and laser nuclear physics,and has accumulated extensive expertise in laser technology and experimental methodologies.To further advance studies in precision high-energy-density physics and empower exploration of frontier applications—thereby transitioning petawatt femtosecond laser systems from“demonstration devices”to“practical tools”—Peking University,through the Beijing Laser Acceleration Innovation Center（BLAIC）,has independently developed a high-repetition-rate,petawatt-class,femtosecond laser facility.The laser system is a chirped pulse amplification （CPA） architecture based on a Ti∶sapphire final amplifier,capable of delivering 200 TW and 1 PW-class femtosecond （～30 fs） laser pulses at a repetition rate of 1 Hz.The laser system is designed with two independent front ends one is a conventional front end[abbreviated as the cross-polarized wave （XPW） front end]composed of a CPA1 system based on a Ti∶sapphire regenerative amplifier and an XPW filter system.The other is a high-contrast front end based on an optical parametric chirped-pulse amplification （OPCPA） system pumped by an ultrafast Yb∶YAG solid-state laser,amplifying signal light at a central wavelength of 1600 nm,combined with second harmonic generation（SHG） technology.The seed signal for this front end is generated through white-light supercontinuum generation （WLG） pumped by the same Yb∶YAG laser.This paper presents recent work based on the XPW frontend.The CPA2 optical system is shared by both frontends and comprises an?ffner stretcher,five-stage multi-pass amplifiers,and a Treacy compressor.The first amplifier is a 1 kHz pre-amplifier,while the remaining stages operate at 1 Hz.We achieve the output of 224.7 TW femtosecond laser pulses at a 1 Hz repetition rate.The compressed pulse duration is 26.4 fs,with a beam diameter of about 80 mm,and a temporal contrast baseline of1×10-9 at 100 ps （XPW frontend）.Building upon the 200 TW platform,we have further completed the design and construction of a 1 Hz,1 PW amplification system.Key accomplishments include the testing of a high-quality pump laser,optimization of pump and seed laser parameters,and implementation of crystal thermal management and parasitic oscillation suppression.The PW amplifier employs four pump lasers operating at a central wavelength of 532 nm and a repetition rate of 1 Hz.These lasers deliver high-quality,linearly polarized output with the following specifications:a maximum energy of 8×14 J,long-term energy stability of<1%[standard deviation （STD）]over8 h,top-hat beam profile uniformity of<1.6,and time jitter of<0.3 ns （STD,300 shots）.Through the formulation of a refractive index-matching fluid and the design of a dual-circulation cooling system,combined with active regulation of the pump laser timing,we have successfully suppressed parasitic oscillation in the PW amplifier and stabilized the temperature rise in the crystal.Ultimately,the PW amplifier based on the XPW frontend has achieved an amplified energy of approximately 48.7 J,with energy stability of about0.9%（STD） over 600 consecutive shots.The pulses are compressed to 28.4 fs in air,achieving a compression efficiency of approximately 71.0%.These results demonstrate that the BLAIC-1 PW laser system possesses the capability of delivering femtosecond laser pulses at a repetition rate of 1 Hz with a peak power of 1.2 PW.Conclusions and Prospects Ultra-intense ultrafast lasers are playing an increasingly important role in exploring extreme states of matter under strong electromagnetic field conditions,while researchers are placing new demands on increasing the average power of such lasers without compromising high peak powers.High-repetition-rate petawatt femtosecond lasers represent not only a leap in performance but also a critical step from“demonstration devices”to“practical tools,”paving the way for practical applications of strong-field physics and its derived technologies.The self-developed high-repetition-rate （1 Hz）,petawatt （1 PW）,femtosecond（30 fs） laser facility at the BLAIC will provide a robust platform for cutting-edge research such as applying laser-accelerated protons to cancer therapy.更多还原