High power,widely tunable femtosecond MgO:PPLN optical parametric oscillator

We demonstrate a high power,widely tunable femtosecond MgO-doped periodically poled lithium niobate(MgO:PPLN)optical parametric oscillator(OPO)at 151 MHz,pumped by a Kerr-lens mode-locked Yb:KGW laser.With a maximum pump power of 7 W,the OPO is capable of delivering as high as 2.2 W of the signal centered around 1500 nm with tunable signal spectrum ranges of 1377 nm-1730 nm at an extraction efficiency of 31.4%,which exhibits a long-term passive power stability better than 0.71%rms over 4 h.The maximum idler bandwidths of 185 nm at 3613 nm are obtained across the idler tuning ranges of 2539 nm-4191 nm.By compensating intracavity dispersion,the signal has the shortest pulse duration of 170 fs at 1428 nm.

皮秒激光泵浦的亚10fs钛宝石激光器

研制了高稳定Nd∶YVO_4皮秒激光振荡器,并在15 W、808nm激光泵浦下得到6 W的连续锁模皮秒激光输出,光-光效率为40%.对该皮秒激光进行单通放大后得到14 W的基频光输出,倍频后可以得到7 W的532nm皮秒激光,用作钛宝石振荡器的泵浦源.在4.5 W的皮秒532nm激光泵浦下,结合腔外压缩,得到了脉宽为9.4fs、平均功率为150mW的脉冲序列输出.调节钛宝石振荡器的腔长使其与皮秒振荡器的腔长一致时,可实现自触发克尔透镜锁模.实验结果表明皮秒激光泵浦可以有效地触发钛宝石激光器的自动锁模,输出飞秒脉冲序列.

Generation of Femtosecond Laser Pulse at 1.43 GHz from an Optical Parametric Oscillator Based on LBO Crystal

A femtosecond LBO optical parametric oscillator(OPO)with widely adjustable repetition rate by fractionally decrement of the cavity length is demonstrated.The repetition rate of 755 MHz to 1.43 GHz at an interval of 75.5 MHz is realized,which is 10 to 19 times that of the pump laser.The properties of output signal at 750 nm at different repetition rates are studied.The power of signal decreases with increasing the repetition rate.The maximum power of 194 mW at the repetition rate of 755 MHz and the minimum power of 22 mW at repetition rate of 1.43 GHz for the signal at 750 nm are obtained for the pump power of 3 W.

超强激光在均匀等离子体中的背向拉曼散射放大机制

使用等离子体背向受激拉曼散射对激光进行放大时,等离子体的密度、温度和长度都会对激光的放大效果产生影响.为了探究等离子体密度对结果的影响,本文使用一维粒子模拟程序模拟了波长为800 nm的泵浦激光入射到均匀等离子体中,等离子体密度和泵浦光光强对散射光光谱的影响.模拟结果表明,等离子体密度降低会导致散射光的波长变短,而泵浦光的光强在一定范围内降低会增加散射光中背向散射光的比例.通过分析散射光的光强和等离子体的密度,发现前向拉曼散射是等离子体密度变化的原因.模拟结果对等离子体背向受激拉曼散射放大的实验研究具有重要的指导意义.

All-fiber laser seeded femtosecond Yb:KGW solid state regenerative amplifier

A high efficiency compact Yb:KGW regenerative amplifier using an all-fiber laser seed source was comprehensively studied.With thermal lensing effect compensated by the cavity design,the compressed pulses with energy of 1 mJ at 1 kHz and 0.4 mJ at 10 kHz in sub-400-fs pulse duration using chirped fiber Bragg grating(CFBG)stretcher were demonstrated.A modified Frantz-Nodvik equation was developed to emulate the dynamic behavior of the regenerative amplifier.The simulation results were in good agreement with the experiment.Numerical simulations and experimental results show that the scheme can be scalable to higher energy of multi-mJ,sub-300 fs pulses.

A 515-nm laser-pumped idler-resonant femtosecond BiB_(3)O_(6) optical parametric oscillator

We report on an idler-resonant femtosecond optical parametrical oscillator(OPO)based on BiB_(3)O_(6)(BiBO)crystal,synchronously pumped by a frequency-doubled,mode-locked Yb:KGW laser at 515 nm.The idler wavelengths of OPO can be tuned from 1100 nm to 1540 nm.At a repetition rate of 75.5 MHz,the OPO generates as much as 400 mW of idler power with 3.1 W of pump power,the corresponding pulse duration is 80 fs,which is 1.04 times of Fourier transform-limited(FTL)pulse duration at 1305 nm.In addition,the OPO exhibits excellent beam quality with M^(2)<1.8 at 1150 nm.To the best of our knowledge,this is the first idler-resonant femtosecond OPO pumped by 515 nm.

A Self-Diffraction Temporal Filter for Contrast Enhancement in Femtosecond Ultra-High Intensity Laser

We demonstrated a nonlinear temporal filter based on the self-diffraction(SD)process.Temporal contrast enhancement,angular dispersion and spectrum broadening properties of the SD process are investigated in experiment and simulation.Driven by spectral phase well compensated laser pulses with bandwidth of 28 nm,the filter produced clean pulses with a temporal contrast higher than 10^(10) and excellent spatial profile,the spectrum of which was smoothed and broadened to 64 nm.After implementing this filter into a home-made 30 TW Ti:sapphire amplifier,temporal contrast of the amplified pulses was enhanced to 10^(10) within the time scale of−400 ps.

Harmonically pump a femtosecond optical parametric oscillator to 1.13 GHz by a femtosecond 515 nm laser

We demonstrate a harmonically pumped femtosecond optical parametric oscillator(OPO)laser using a frequency-doubled mode-locked Yb:KGW laser at a repetition rate of 75.5 MHz as the pump laser.Based on a bismuth borate nonlinear crystal,repetition rates up to 1.13 GHz are realized,which is 15 times that of the pump laser.The signal wavelength is tunable from 700 nm to 887 nm.The maximum power of the signal is 207 m W at the central wavelength of 750 nm and the shortest pulse duration is 117 fs at 780 nm.The beam quality(M^2 factor)in the horizontal and vertical directions of the output beam are 1.077 and 1.141,respectively.

Generation of 601 fs pulse from an 8 kHz Nd:YVO_(4) picosecond laser by multi-pass-cell spectral broadening

We demonstrate nonlinear pulse compression of an 8 k Hz Nd:YVO4 picosecond laser using the multi-pass-cell(MPC) technique with fused silica as the nonlinear medium. The pulse duration is compressed from 12.5 ps to 601 fs, corresponding to a pulse shortening factor of 20.8. The output pulse energy is 154 μJ with an efficiency of 74.5%. To the best of our knowledge,this is the highest pulse compression ratio achieved in a single-stage MPC with bulk material as the nonlinear medium. The laser power stability and the beam quality(M2) before and after the MPC are also experimentally studied. Both the laser power stability and the beam quality are barely deteriorated by the MPC device.

Diode-pumped 13 W Yb:KGW femtosecond laser

We report on a high-power diode-pumped Yb∶KG(WO_(4))_(2)(Yb:KGW) mode-locked laser with a semiconductor saturable absorber mirror(SESAM). For 32.7 W of incident pump power, we generate 261 fs pulses with the maximum average output power of up to 13.0 W and spectrum centered around 1039 nm at 68.4 MHz, corresponding to 190 n J of single pulse energy and0.72 MW of peak power. The optical-to-optical conversion efficiency is 39.8%, and the slope efficiency is 64.4%. The Yb:KGW laser exhibits a power stability better than 0.543% of the root-mean-square in 2 h.