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.     

GHz重复频率亚百飞秒克尔透镜锁模Yb:CaYAlO4激光器

GHz重复频率飞秒激光具有高单纵模功率和高采样速率等优点,在科学前沿和工业加工等领域具有重要的应用价值.受限于锁模原理和泵浦源的可用功率, GHz重复频率克尔透镜锁模激光器的平均输出功率通常仅为数十到百毫瓦量级,限制了其直接应用.基于此,本文报道了利用高功率单模光纤激光器泵浦的GHz重复频率高功率克尔透镜锁模飞秒激光器.通过合理的腔模设计,构建了四镜环形腔结构,使晶体中激光模式可以和整形后的泵浦光形成良好匹配,以利于软孔克尔透镜锁模的实现.在8 W的泵浦功率下,首次在Yb:CaYAlO₄激光器中实现了GHz重复频率的亚百飞秒高功率锁模运转,平均输出功率为2.1 W,重复频率为1.8 GHz,脉冲宽度为88 fs,对应峰值功率大于10 kW.该实验结果表明Yb:CaYAlO₄晶体具有产生GHz重复频率高功率飞秒激光的潜力,高功率短脉宽GHz飞秒激光器可为光学频率梳和微加工等领域提供优质光源.     

A 515-nm laser-pumped idler-resonant femtosecond BiB3O6 optical parametric oscillator

We report on an idler-resonant femtosecond optical parametrical oscillator(OPO)based on BiB₃O₆(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 M²<1.8 at 1150 nm.To the best of our knowledge,this is the first idler-resonant femtosecond OPO pumped by 515 nm.     

夫琅禾费衍射公式的一般形式

从不同的途径导出了大角度情形下亦成立的夫琅禾费衍射积分的一般形式，指出此一般形式公式是求解夫琅禾费衍射的基本公式．并通过对夫琅禾费衍射公式的级数形式的推导，揭示了傅里叶光学中“夫琅禾费衍射公式”与一般形式公式存在的差别，以及消除这种差别的措施．此外，还较详细地讨论了倾斜因子对衍射花样的影响．这对于衍射测量及深入理解夫琅禾费衍射的本质有一定的指导意义．     

两台独立飞秒钛宝石振荡器的高精度主动同步研究

对两台独立钛宝石飞秒振荡器的高精度主动同步进行了研究.实验中共采用三套锁相环对它们输出的激光脉冲进行了主动同步控制，最终得到了时间抖动低于30fs的同步精度；由于通过计算机智能监控两台振荡器的相对腔长变动，使得高精度同步维持的时间高达40min.     

A 12.1-W SESAM mode-locked Yb:YAG thin disk laser

Pumped by a 940 nm fiber-coupled diode laser, a passively mode-locked Yb:YAG thin disk oscillator was demonstrated with a semiconductor saturable absorber mirror(SESAM). 12.1 W mode-locked pulses were obtained with pulse duration of 698 fs at the repetition rate of 57.43 MHz. Measurement showed that the beam quality was close to the diffraction limit.     

PPLN晶体差频测量飞秒激光脉冲的载波包络相移

在飞秒激光频率梳系统中，通常采用自参考技术测量飞秒激光脉冲的载波包络相移，但该技术需要采用光子晶体光纤进行光谱扩展从而增加了系统的不稳定性，这种技术已经制约了高稳定度的飞秒激光频率梳的发展.采用PPLN晶体差频法测量了宽谱钛宝石振荡器输出的7fs激光脉冲的载波包络频移，得到了大于30dB的拍频信号，为研制无光纤的新一代高稳定度光学频率梳奠定了基础.     

Tunable femtosecond laser in the visible range with an intracavity frequency-doubled optical parametric oscillator

We demonstrated experimentally a synchronously pumped intracavity frequency-doubled femtosecond optical parametric oscillator (OPO) using a periodically-poled lithium niobate (PPLN) as the nonlinear material in combination with a lithium triborate (LBO) as the doubling crystal. A Kerr-lens-mode-locked (KLM) Ti:sapphire oscillator at the wavelength of 790 nm was used as the pump source, which was capable of generating pulses with a duration as short as 117 fs. A tunable femtosecond laser covering the 624-672 nm range was realized by conveniently adjusting the OPO cavity length. A maximum average output power of 260 mW in the visible range was obtained at the pump power of 2.2 W, with a typical pulse duration of 205 fs assuming a sech2 pulse profile.     

飞秒钛宝石放大激光脉冲的载波包络相位测量与控制

通过对重复频率为1 kHz的放大飞秒激光脉冲的光谱干涉实验,结合傅里叶变换进行了载波包络相位漂移的实验研究.在此基础上利用锁相环反馈控制技术实现了对载波包络相位的精密锁定,锁定后的激光脉冲稳态相位均方根误差小于80mrad,锁定时间超过3h.同时在理论上分析了光谱干涉测量放大激光脉冲载波包络相位的原理,给出了光谱干涉信号与载波包络相位的关系. 关键词： 飞秒钛宝石放大器 载波包络相位 光谱干涉 超连续