Yb-doped mixed sesquioxides for ultrashort pulse generation in the thin disk laser setup

We report on spectroscopic investigations of the mixed sesquioxide laser materials Yb:LuScO₃, Yb:YScO₃, and Yb:(Lu,Y,Sc)₂O₃ as well as mode-locked thin disk laser experiments with Yb:LuScO₃ and Yb:(Lu,Y,Sc)₂O₃. The disordered crystal structures of these materials result in significantly broader emission spectra than for the pure sesquioxides Yb:Sc₂O₃, Yb:Y₂O₃, and Yb:Lu₂O₃ providing a high potential for ultrashort pulse generation. In SESAM mode-locked thin disk laser experiments, pulse durations of around 100 fs could be obtained exploiting >70 % of the gain bandwidth which is to the best of our knowledge the optimum obtained so far for the mode-locked lasers in this setup.     

Low-repetition rate,nanosecond,high-power pulse amplifier system based on Yb-doped rod-type fiber

We report a nanosecond-pulse amplification system based on an Yb-doped,100-μm core,rod-type photonic crystal fiber.Up to 10 W of average power with pulse energy of 1 mJ and peak power of 450 kW is obtained at the repetition rate of 10 kHz.The high-power nanosecond pulse has a good pulse shape and spectral characteristics.The usage of rod-type fibers provides a novel structure for nanosecond pulse amplification.     

超短脉冲染料放大器中的参数研究

对超短脉冲染料放大器(DLA)中放大的自发辐射(ASE)随泵浦强度变化的关系进行了实验研究,为了求得具有高储能、低自发辐射背景噪声的染料激光放大器的泵浦强度,我们用速率方程对实验结果进行了解析分析,获得了染料激光放大器的泵浦强度与染料参数(浓度、增益长度等)的近似关系式,以及相应条件下染料激光放大器储能和小信号增益的表达式,并与实验进行了比较.二者符合较好,从而为染料激光放大器的设计提供了参考.     

高功率超短激光脉冲信噪比的研究

 针对高功率激光系统中信噪比低的问题，基于描述超短脉冲传输的非线性薛定谔方程进行数值模拟，研究了高阶群速度色散、光谱调制及自相位调制对脉冲信噪比的影响；新建立了用于分析光栅平整度对脉冲信噪比的影响的物理模型并进行了相应的模拟，分析了光栅的质量要求或补偿精度。研究表明：对于100 fs的高斯脉冲，要保证信噪比达到10⁸，应将三阶色散量限制在4.8×10⁵ fs³以下，B积分的值应小于0.2，光谱的调制幅度应小于10^-4，光栅平整度应优于λ/100。     

All-fiber millijoule energy and nanoseconds pulse operation of a high beam quality multi-stage pulse-pumped Yb-doped amplifier cascade

We report on an all fiber Master Oscillator Power Amplifier (MOPA) structured pulsed-pumped fiber-amplifier seeded by laser diode and modulated by current with an output of several nanojoule energy at 100 Hz repetition rate. To suppress ASE, pulse-pumped technology was adopted in four stages of amplification. By means of this technology, repetition could be adjusted freely without change of pump current which is different from continuous pump. 80 μJ output was achieved in 18 ns pulses in the 15 μJ amplification stage. Moreover, we achieved over 1.2 mJ/pulse with pulses of 10 ns between 1 Hz to 100 Hz repetition in the 30 μm core amplification stage with output beam quality of M ² ≈ 1.4. Energy was limited by launched pump power.     

超短激光脉冲二倍频理论分析

采用快速傅里叶变换（FFT）算法和Rung-Kutta法对KDP晶体中超短激光脉冲二倍频过程作了研究。详细讨论了群速度失配、群速度色散和三阶非线性相位调制效应对倍频光脉冲波形、光谱及转换效率的影响。研究结果表明：在超短激光脉冲二倍频中，三阶非线性相位调制效应可使二倍频光脉冲形状发生畸变，光谱明显展宽且转换效率降低；当入射基频光功率密度大于100GW/cm2时，三阶非线性效应是影响倍频过程的主要因素。     

电子束泵浦KrF激光器进行超短脉冲的单束放大实验研究

电子束泵浦KrF激光器口径大、泵浦率高 ,可直接用于进行超短脉冲激光的放大。用天光一号电子束泵浦KrF激光器进行超短脉冲激光放大 ,将超短脉冲激光放大到 2～ 3J、1.2 ps,激光功率达到 2TW。测量了石英窗镜中的非线性吸收系数和超短脉冲激光脉宽的变化     

High-energy soliton pulse generation with a passively mode-locked Er/Yb-doped multifilament-core fiber laser

We report the generation of high-energy short pulses from a mode-locked erbium/ytterbium-doped large-mode-area multifilament-core fiber laser operating in the purely anomalous dispersion regime. The self-starting fiber laser emits 400 mW of average output power at a pulse repetition rate of 44 MHz, corresponding to a pulse energy of 9.1 nJ. The laser produces near transform-limited output pulses with pulse duration of 1.6 ps, corresponding to 5 kW peak power. This new type of low-nonlinearity fibers demonstrates the power and energy scaling potential of fiber-based short pulse lasers in the eye-safe region.     

High-peak-power nanosecond pulse generation by stimulated Brillouin scattering pulse compression in a seeded Yb-doped fiber amplifier

We demonstrate the generation of nanosecond and multikilowatt peak-power pulses in a double-clad Yb-doped fiber amplifier seeded by a spectrally narrowed gain-switched laser diode. Injected pulses with 100 ns duration were simultaneously compressed and amplified by the combination of high amplifier gain and stimulated Brillouin scattering. A maximum peak power of 20 kW has been obtained, corresponding to a single-pass gain of +57 dB in terms of peak power. Part of this output signal was also converted into IR continuum light by splicing a length of single-mode fiber at the end of the fiber amplifier.     

掺镱光纤放大器泵浦脉宽优化

为抑制低重复频率高能脉冲光纤主振荡功率放大(MOPA)系统的放大自发辐射(ASE)效应,达到脉冲泵浦的最佳放大效果,需要对泵浦脉宽进行优化。基于求解速率方程和功率传输方程,理论研究了脉冲泵浦下掺镱光纤放大器上能级粒子数密度、光纤内存储能量、正反向放大自发辐射的瞬态响应。在给定的泵浦功率、光纤长度、纤芯面积和掺杂数密度等参数下,数值计算得到的优化泵浦脉宽为793 s。此外,实验测定了ASE的建立时间; 通过调节泵浦脉宽,测定了脉冲泵浦下掺镱光纤放大器的放大效果,实验中得到的泵浦脉宽的优化值为800 s,证明了数值模拟的正确性。     

Refractive system for generation of high-power diffraction-free laser beams

A refractive system is designed to convert a high-power annular beam into a circular Bessel beam. The input and output surface of the proposed system is derived. We provide cubic polynomial approximation of the surface profiles. A ray tracing through the complete system is provided to verify the design. The design parameters can be selected to choose the desired beam power in the central lobe and length of the refractive system.     

Femtosecond pulse generation and amplification in Yb-doped fibre oscillator-amplifier system

In recent times ytterbium (Yb) doped fibre-based mode-locked master oscillator and power amplifier have attracted a great deal of interest because of their inherent advantages like flexibility, reliability, compactness, high power handling capability and diffraction limited output beam quality as compared to the solid-state counterpart. But, to successfully develope of high-power femtosecond oscillator-amplifier system based on Ybdoped fibre, an appropriate choice of the mode-locking regime and the amplifier geometry are required. Development of an all-fibre integrated high-power Yb-doped fibre oscillator-amplifier system in which the advantages of a fibre-based system can be fully exploited remained a challenge as it requires the careful optimization of dispersion, nonlinearity, gain and ASE contribution.     

高功率超短激光脉冲信噪比的研究

针对高功率激光系统中信噪比低的问题,基于描述超短脉冲传输的非线性薛定谔方程进行数值模拟,研究了高阶群速度色散、光谱调制及自相位调制对脉冲信噪比的影响;新建立了用于分析光栅平整度对脉冲信噪比的影响的物理模型并进行了相应的模拟,分析了光栅的质量要求或补偿精度。研究表明：对于100 fs的高斯脉冲,要保证信噪比达到108,应将三阶色散量限制在4.8×105 fs3以下,B积分的值应小于0.2,光谱的调制幅度应小于10-4,光栅平整度应优于λ/100。     

Stable nanosecond pulse generation from a graphene-based passively Q-switched Yb-doped fiber laser

We demonstrate stable 70?ns pulse generation from a Yb-doped fiber laser passively Q-switched by a graphene-based saturable absorber mirror in a short linear cavity. The maximum output power was 12?mW and the highest single pulse energy was 46?nJ. The repetition rate of the fiber laser can be widely tuned from 140 to 257?kHz along with the increase of the pump power. To the best of our knowledge, this is the first report for passively Q-switched sub-100-ns pulse operation of a graphene-based saturable absorber in a Yb-doped fiber laser.     

High-power all-normal-dispersion femtosecond pulse generation from a Yb-doped large-mode-area microstructure fiber laser

We report on an all-normal-dispersion mode-locked fiber laser based on a large-mode-area Yb-doped microstructure fiber and using a high nonlinear modulation depth semiconductor saturable absorber mirror. The laser delivers 3.3 W of average output power with positively chirped 5.5 ps pulses at a center wavelength of 1033 nm. The pulse repetition rate is 46.4 MHz, which results in an energy per pulse of 71 nJ. These pulses are extracavity dechirped down to 516 fs by using bulk gratings. The average power of the dechirped pulses is 2.3 W, which corresponds to a peak power of more than 96 kW.     

Experimental generation of high-contrast Talbot images with an ultrashort laser pulse

A femtosecond Ti:sapphire laser oscillator emitting pulses with 800 nm central wavelength, 10.9 fs pulse width, and 75 MHz repetition rate, combined with a dispersion-compensated diffractive system, was used to implement a large-area, high-contrast, broadband optical interference technique based on the Talbot effect. Chromatic artifacts associated with the huge spectrum of the optical source (approximately 150 nm) are compensated for with an air-separated hybrid diffractive-refractive lens doublet. The spatial resolution of the chromatically compensated Talbot images under femtosecond illumination is nearly identical to that achieved under continuous wave monochromatic illumination. Furthermore, the temporal width of the signal at the Talbot planes is limited by the group-delay-dispersion coefficient which is shown to be small. High-contrast one-dimensional periodic structures of 96.1 μm spacing generated by Talbot diffractometry are experimentally demonstrated.     

Phase locking in four-wave Raman mixing for generation of an ultrashort laser pulse

The emission lines generated by four-wave Raman mixing were coherently phased and provided an approximately 30-fs pulse without any loss of energy simply by passage of the pulse beam through molecular hydrogen.     

电子束泵浦KrF激光器进行超短脉冲的单束放大实验研究

 电子束泵浦KrF激光器口径大、泵浦率高，可直接用于进行超短脉冲激光的放大。用天光一号电子束泵浦KrF激光器进行超短脉冲激光放大，将超短脉冲激光放大到2~3J、1.2ps, 激光功率达到2TW。测量了石英窗镜中的非线性吸收系数和超短脉冲激光脉宽的变化。     

Quasiperiodic Raman technique for ultrashort pulse generation

We report the experimental demonstration of a new Raman technique that produces 200 sidebands, ranging in wavelength from 3 microm to 195 nm. By studying multiphoton ionization of nitric oxide (NO) molecules, we show mutual phase coherence among 15 visible sidebands covering 0.63 octaves of bandwidth.     

紫外超短脉冲激光放大过程中脉宽压缩的方案设计

采用放电泵浦KrF准分子激光放大器放大波长为248.4nm的紫外超短脉冲激光。对于能量为0.7mJ、脉宽为550fs的输入脉冲,在光束直径保持10mm不变的条件下,能量放大到15mJ,脉宽展宽到1200fs。为了压缩输出脉冲宽度,分析了群速度色散和自相位调制效应对脉宽展宽的影响。利用棱镜对,采用4种不同的实验方案对脉冲引入负的线性频率啁啾,以补偿KrF准分子激光放大器CaF2窗镜中的群速度色散和自相位调制对脉冲引入的正的线性频率啁啾。结果表明:在放大器之前放置棱镜对的方式可以在保持输出脉冲能量为15mJ的同时,在棱镜对间距为110cm的条件下,将输出脉冲宽度压缩到370fs,输出波长为248.4nm、带宽为0.4nm。