High-Conversion-Efficiency and Broadband Tunable Femtosecond Noncollinear Optical Parametric Amplifier

We build a compact high-conversion-efficiency and broadband tunable noncollinear optical parametric amplifier （OPA） in the infra-red （IR） pumped by a femtosecond Ti：sapphire CPA laser. The OPA consists of an internal seed of white-light continuum generator （WLG） and two noncollinear optical parametric amplifiers. The tunable wavelength range is from 1.2μm to 2.4μm for both signal and idle pulses. The total OPA efficiency in the last OPA stage reaches about 40% in a wider tunable spectral range （from 1.3μm to 1.7μm for signal pulse, from 1.5μm to 2.0 μm for idle pulse respectively）.     

高品质激光尾波场电子加速器

激光尾波场电子加速的加速梯度相比于传统直线加速器高了3—4个量级,对于小型化粒子加速器与辐射源的研制具有重要的意义,成为当今国内外的研究热点.台式化辐射源应用需求的提高,特别是自由电子激光装置的快速发展,对电子束流品质提出了更高的要求,激光尾波场电子加速的束流品质和稳定性是目前实现新型辐射源的首要障碍.本文归纳整理了中国科学院上海光学精密机械研究所电子加速研究团队十年来在研制台式化激光尾波场电子加速器过程中采取的方案和取得的进展.例如率先提出了注入级和加速级分离的级联加速方案,通过实验获得了GeV量级的电子束能量;基于级联加速方式利用能量啁啾控制,实验获得世界最高品质的电子束流;通过优化激光系统稳定性和特殊的气体喷流结构,获得稳定的高品质电子束流输出等.这一系列实验结果有利于进一步推进激光尾波场电子加速器的应用.     

双轴晶体光学参量放大的研究

介绍了新近提出的光学啁啾脉冲参量放大技术,并以高增益、宽谱带的双轴非线性晶体LBO为例,研究了抽运光和信号光的相位匹配的关系、增益、增益带宽、匹配角的选择,以及增益随晶体长度变化的趋势和双曲正割和高斯脉冲输入非线性晶体前后变化的情况。     

Effect of the Initial Laser Phase on the Interaction Between Relativistic Electron and Ultra－Intense Laser Field in a Strong Uniform Magnetic Field

We investigate the influence of the initial laser phase on the interaction between relativistic electron and ultraintense linear polarized laser field in a strong uniform magnetic field. It is found that the dynamic behaviour of the relativistic electron and the emission spectrum varies dramatically with different initial laser field phases.The effect of changing initial phase is contrary in the two parameter regions divided by the resonance condition.The phase dependence of the electron energy and velocity components are also studied. Some beat structure is found when the initial laser phase is zero and this structure is absent when the initial laser phase is a quarter of a period.     

用SPIDER法测量15 TW/35 fs强激光系统的脉冲输出特性

利用光谱位相干涉直接重构光脉冲的方法 (SPIDER) ,对最近建成的 15TW 35fs台式掺钛蓝宝石超短超强激光系统的输出脉冲特性进行了测量。测量内容包括输出脉冲的相对位相分布和脉冲强度随时间的变化情况。结果显示 ,输出脉冲具有好的相对位相分布 (各光谱之间相对位相差 <2π) ,输出脉冲半高宽为 33fs,表明此系统的脉冲输出已经达到了设计的要求。     

基于光场的超快相干电子源产生及调控研究进展(特邀)

光与物质之间的相互作用是自然界中最基本的物质相互作用之一,这种动力学的完全可视化需要时间上的阿秒分辨率和空间上的原子级分辨率.超短相干电子源是实现这一目标的重要方法.本文介绍了利用各种光场如射频、太赫兹、可见光来产生、相空间调控甚至表征这种超短相干的高品质电子源的重要进展,并主要总结了其在四维超快电子显微镜方面的技术突...     

周期性极化铌酸锂晶体中半非共线型宽带光学参变放大理论研究

基于周期性极化铌酸锂晶体(PPLN)的准相位匹配光参变放大过程,通过倾斜周期极化铌酸锂晶体中极化域(极化光栅)一定角度,实现了介于共线匹配方式和非共线匹配方式之间的一种半非共线型准相位匹配方式,并以该匹配方式下的各光矢量几何关系得出相位匹配曲线,找到在特定抽运光和信号光波长下能获得宽带增益放大的周期极化长度。并研究其极化倾斜角度与温度特性。模拟计算表明,在合适的角度与温度条件下,该方式可以532 nm抽运光抽运的信号光在800 nm和1064 nm处均获得宽带光参变放大。     

100-GeV large scale laser plasma electron acceleration by a multi-PW laser

We present three possible design options of laser plasma acceleration (LPA) for reaching a 100-GeV level energy by means of a multi-petawatt laser such as the 3.5-kJ, 500-fs PETawatt Aquitane Laser (PETAL) at French Alternative Energies and Atomic Energy Commission (CEA). Based on scaling of laser wakefield acceleration in the quasi-linear regime with the normalized vector potential a0 =1.4(1.6), acceleration to 100 (130) GeV requires a 30-m-long plasma waveguide operated at the plasma density n e ≈ 7×10 15 cm-3 with a channel depth Δn/ne = 20%, while a nonlinear laser wakefield accelerator in the bubble regime with a0≥2 can reach 100 GeV approximately in a36/a0-m-long plasma through self-guiding. The third option is a hybrid concept that employs a ponderomotive channel created by a long leading pulse for guiding a short trailing driving laser pulse. The detail parameters for three options are evaluated, optimizing the operating plasma density at which a given energy gain is obtained over the dephasing length and the matched conditions for propagation of relativistic laser pulses in plasma channels, including the self-guiding. For the production of high-quality beams with 1%-level energy spread and a 1π-mm-mradlevel transverse normalized emittance at 100-MeV energy, a simple scheme based on the ionization-induced injection mechanism may be conceived. We investigate electron beam dynamics and effects of synchrotron radiation due to betatron motion by solving the beam dynamics equations on energy and beam radius numerically. For the bubble regime case with a0=4, radiative energy loss becomes 10% at the maximum energy of 90 GeV.     

Flat-top phase-matched high-order harmonics in gas-filled cell

Phase-matched high-order harmonic generation in Ar gas-filled cell is investigated experimentally. We obtain phase-matched 27th order harmonic driven by a commercially available solid-state femtosecond laser system at 0.55 mJ/pulse energy level and 1-kHz repetition rate. Moreover, we find that the spatial distribution of intensity of high-order harmonics is flat-top profile other than a Gaussian one under the condition of optimized conversion efficiency in the static gas cell.     

超连续谱干涉方法测量古依相移

利用两束超连续光干涉得到的信号,测量了透镜焦点附近飞秒激光脉冲的古依(Gouy)相移。根据得到的光谱干涉信号,利用傅里叶变换得到相对相位值。激光光束在聚焦透镜后的束腰半径可以由成像方法测得。根据测量得到的激光光束束腰半径,用非线性拟合的方法得到了古依相移曲线,拟合曲线与实验结果符合得非常好。给出了古依相位在焦点前后1 mm区域内的移动量。