光阴极RF腔注入器中激光脉冲的时间抖动

介绍光阴极RF腔注入器中的驱动激光器,采用二极管泵浦的自锁模激光器,通过锁相,使输出激光脉冲的时间抖动小于2ps,实现激光脉冲同微波相位之间的严格同步,在实验上获得流强70A、能量2MeV、亮度4.4×1011A/(m2.rad2)的电子束。     

阴极强流多脉冲发射特性研究

实验研究了几种阴极的强流猝发多脉冲发射特性. 研究结果表明, 天鹅绒阴极产生的猝发强流双脉冲电子束亮度优于1×10⁸A/(m.rad)², 而直立碳纤阴极产生的强流三脉冲电子束的亮度也优于3×10⁷A/(m.rad)², 并有进一步提高的可能. 新型的冷场致发射阴极如纳米金刚石膜阴极和纳米碳管阴极也具有强流发射能力, 实验得到的发射电流密度大于50A/cm².文中还给出的大发射面储备式热阴极的实验结果, 并对相关阴极实现稳定强流多脉冲发射的研究方向和应用前景进行了分析.     

光阴极注入器的驱动激光器

 光阴极注入器要求驱动激光器的激光时间抖动小、脉冲宽度窄、激光波长短和脉冲功率高。从原理和实验上介绍光阴极注入器的驱动激光器,包括连续波锁模振荡腔、时间同步,激光脉冲功率放大等;该激光器输出激光微脉冲宽度10ps,微脉冲时间抖动小于2ps,宏脉冲宽度2.5 μs, 峰值功率100kW, 已用于光阴极RF腔注入器实验,并获得了很好的结果。     

北京大学高平均流强光阴极电子枪驱动激光系统

DC-SC超导光阴极注入器将直流光阴极电子枪和超导加速腔结合在一起,其特点之一是适合于提供高平均流强电子束.文中介绍了直流光阴极电子枪的驱动激光系统的研制.该驱动激光系统的主机为瑞士TBP公司的GE-100-XHP型激光器,是采用可饱和吸收镜技术的被动锁模激光器,其工作晶体为Nd:YVO₄,输出波长为1064nm,脉冲重复频率为81.25MHz,平均功率10W.该驱动激光系统配套的CLX-1100同步控制器可以将激光脉冲与射频参考信号严格锁定,随机抖动不大于1ps.根据使用要求,作者研制了高效的激光倍频器,获得了大于1W的266nm紫外激光.同时,激光到光阴极的传输设计中,采用了傅立叶光学技术,在紫外激光功率650mW左右的条件下,从自行研制的Cs₂Te光阴极上实现了大于500μA的光电流引出     

光阴极注入器的驱动激光器

光阴极注入器要求驱动激光器的激光时间抖动小、脉冲宽度窄、激光波长短和脉冲功率高。从原理和实验上介绍光阴极注入器的驱动激光器,包括连续波锁模振荡腔、时间同步,激光脉冲功率放大等;该激光器输出激光微脉冲宽度10ps,微脉冲时间抖动小于2ps,宏脉冲宽度2.5 μs, 峰值功率100kW, 已用于光阴极RF腔注入器实验,并获得了很好的结果。     

LD预泵浦条件与Cr4+,Nd3+:YAG微片激光器的输出特性

 建立了LD预泵浦的被动调Q平平腔Cr⁴⁺,Nd³⁺:YAG微片激光器模型,分析了预泵浦参数与激光脉冲时间特性的关系,设计了LD预泵浦的Cr⁴⁺,Nd³⁺:YAG微片激光器实验,测量了不同预泵浦参数下激光单脉冲以及脉冲序列的时间特性。实验结果与数值计算结果基本符合：调节预泵浦参数使每个泵浦脉冲刚好对应输出单个激光脉冲时,固定脉冲泵浦宽度,脉冲泵浦速率随连续泵浦速率的增加呈一次函数减小;固定连续泵浦速率,脉冲泵浦速率随脉冲泵浦宽度的增加呈非线性函数减小。结果还表明,激光脉冲半高全宽随整体泵浦速率的增加而减小,峰值功率随整体泵浦速率的增加而增加;当整体泵浦速率在阈值附近变动时,激光单脉冲时间特性的变化最为明显。     

高功率二极管激光器寿命测试

 介绍了高功率激光二极管不同模式的失效机理，分析了激光二极管不同的寿命测试方法；在冷却水温20℃和实际工作温度下分别对封装的激光器进行了寿命测试。根据试验结果得出退化率，推算出准连续二极管激光器在水温20℃，电流90A，占空比为10%（500Hz，200μs）时，平均激光工作寿命为2.19×10⁹次脉冲；冷却水温35℃时，其平均激光工作寿命下降为1.65×10⁹次脉冲。由实验结果分析得出，高功率激光器封装工艺中的焊料沉积和多层焊接技术，以及工作环境温度是影响激光器可靠性和寿命的关键因素。     

光阴极RF腔注入器

 光阴极RF腔注入器是一种强流、窄脉冲(ps量级)、低发射度的电子束源。文章给出了CAEP光阴极RF腔注入器的结构和实验结果,结构主要包括驱动激光器、Cs₂Te阴极制备室、2.5个RF腔、高功率微波源和测量仪器等,其中驱动激光器的参数是影响注入器电子束质量的重要因素;实验上,该光阴极RF腔注入器可稳定输出能量2MeV、流强70A、发射度～4mm.mrad的高亮度电子束流。     

强阿秒XUV激光脉冲下H_2+分子光电子能谱角分布非对称性

利用2D平面模型,求解了描述定向H_{_2}⁺分子和阿秒XUV脉冲相互作用的薛定谔方程,并求得光电子的角度分布．在计算模型中,采用基态1sσ_g和第一激发态2pσ_u的等比例混合态作为初始态,而激光脉冲的光子能量大于电离势,强度为10¹⁴ W/cm²． 计算结果表明,光电子角分布的非对称性和脉冲的宽度密切相关．这种非对称性实际上是由于初始态的基态和激发态的相干振荡而导致的．当使用长脉冲时,这种相干振荡的周期效应就会被平均而消失,从而产生的光电子能谱会呈对称角分布．     

被动谐波锁模掺Yb3+光纤环形激光器

 利用光纤的非线性偏振旋转效应产生可饱和吸收体的锁模机制，从掺Yb³⁺光纤环形激光器中得到稳定高阶谐波锁模光脉冲。理论分析了工作于正色散区的掺Yb³⁺光纤环形激光器的特性。实验中观测到了掺Yb³⁺光纤环形激光器3种不同演化方式产生高阶锁模光脉冲。4阶谐波锁模脉冲（107.2 MHz重复频率）经过1 m长高掺杂Yb³⁺光纤放大器放大后产生了平均功率100 mW，脉宽22.8 ps的脉冲，最后经过光栅压缩得到了平均输出功率20 mW，脉宽307 fs，脉冲中心波长1 051.2 nm，带宽13.76 nm的激光。     

Mode locking of an erbium-doped fiber laser with intra-cavity polarization modulation

Erbium-doped fiber lasers are normally actively mode-locked through amplitude modulation or phase modulation. In this paper, we demonstrate that the laser can also be mode-locked by employing polarization modulation with a polarization-dependent cavity loss. We obtain a nearly transform-limited mode-locked pulse train at 10 GHz repetition rate with timing jitter as low as 164 fs. The timing jitter is only limited by the timing jitter of the driving signal.     

基于阿秒抖动光纤锁模激光器的时钟同步

光纤锁模激光器结构简单, 运转稳定, 且输出的超短脉冲序列具有极高的时钟稳定性, 在抽运探测、脉冲相干合成等要求高精度时钟同步的前沿领域有着广阔的应用前景. 本文通过激光器腔内的电光调制器进行反馈控制, 实现了两台光纤锁模激光器之间的紧密时钟信号同步; 并且通过平衡光学互相关方法, 对残余的时钟误差信号进行了测量, 分辨率达到了13 as. 通过优化激光器的腔内动力学过程及反馈环路的参数, 在[1 Hz, 10 MHz]的积分区间内得到了109 as的残余时钟误差, 对应单台激光器的平均时间抖动为77 as.     

Passively mode-locked glass waveguide laser with 14-fs timing jitter

Ultralow jitter pulse trains are produced from a passively mode-locked, erbium/ytterbium co-doped, planar waveguide laser by use of high-bandwidth feedback control acting on the physical cavity length and optical pump power. Synchronization of a 750-MHz, fundamentally mode-locked laser to an external clock signal yields an ultralow, root-mean-square relative timing jitter of 14.4 fs integrated from 10 Hz to the Nyquist frequency of 375 MHz.     

光阴极微波电子枪中时间抖动对粒子动力学的影响

对光阴极微波电子枪粒子束性能起决定性影响的因素之一就是激光脉冲相对加速微波相位的时间抖动. 对这种时间抖动的测量和反馈控制进行了理论和实验分析, 并对时间抖动对束流品质的影响进行了模拟研究, 得到了利用锁相环回路降低激光脉冲相位噪声的实验经验, 为光阴极微波电子枪中激光与微波相位同步问题提出了解决方法.     

Ultralow-jitter and -amplitude-noise semiconductor-based actively mode-locked laser

We report a semiconductor-based, low-noise, 10.24 GHz actively mode-locked laser with 4.65 fs of relative timing jitter and a 0.0365% amplitude fluctuation (1 Hz to 100 MHz) of the optical pulse train. The keys to obtaining this result were the laser's high optical power and the low phase noise of the rf source used to mode lock the laser. The low phase noise of the rf source not only improves the absolute and relative timing jitter of the laser, but also prevents coupling of the rf source phase noise to the pulse amplitude fluctuations by the mode-locked laser.     

Ultralow-noise mode-locked optical pulse trains from an external cavity laser based on a slab coupled optical waveguide amplifier (SCOWA)

We report the generation of optical pulse trains with 8.5 fs timing jitter (10 Hz to 10 MHz) from a mode-locked semiconductor laser, with a slab coupled optical waveguide amplifier used as the gain element. This is, to our knowledge, the lowest residual timing jitter reported to date from an actively mode-locked laser.     

Measurement of residual phase noise and longitudinal-mode linewidth in a hybridly mode-locked external linear cavity semiconductor laser

We report measurements of the residual phase-noise knee position and longitudinal-mode linewidth of a hybridly mode-locked external linear cavity semiconductor laser as a function of laser cavity length. Excellent agreement between these measurements suggests a direct relationship between rms pulse-to-pulse timing jitter and average longitudinal-mode linewidth. This relationship leads to a fundamental limit in the timing jitter of mode-locked lasers.     

Generation of 10-GHz ultra-short pulses with low time jitter in an actively mode-locked fiber laser

We have experimentally achieved the 8.3-ps ultra-short pulse at 10 GHz repetition rate with the time jitter as low as 590 fs in an actively mode-locked fiber ring laser. The ring-cavity laser is mode-locked by a semiconductor optical amplifier based on cross-gain modulation. The external CW source is modulated with radio frequency signal by an amplitude modulator as the external optical pulses and, then, injected into the fiber ring cavity to achieve active mode locking. Further investigating the laser output characteristics, it indicates that the linewidth of employed CW source affects properties of the generated ultra-short pulse, such as phase noise and time jitter. Ultra-short pulse at high repetition rate with low time jitter can be generated by the optimization of CW laser source.     

Mode-locked fiber laser frequency-controlled with an intracavity electro-optic modulator

We demonstrate a mode-locked, erbium-doped fiber laser with its repetition frequency synchronized to a second fiber laser via an intracavity electro-optic modulator (EOM). With servo control from the EOM (bandwidth approximately 230 kHz) and a slower speed intracavity piezoelectric transducer (resonance at approximately 20 kHz), we demonstrate stabilization of the repetition frequency with an in-loop rms timing jitter of 10 fs, integrated over a bandwidth from 1 Hz to 100 kHz. This represents what is to our knowledge the first time an EOM has been introduced inside a mode-locked laser cavity for fast servo action and the lowest timing jitter reported for a mode-locked fiber laser.