Timing Jitter Induced by White Noise in Mode-locked Solid-state Lasers

A new method is proposed to analyze and calculate the jitters in a modelocked solid-state laser with chirp. A set of motion equations for amplitude, inverse pulse width, chirp, frequency, pulse central position and phase in a femtosecond mode-locked solid-state laser are derived, and then the jitter induced by white noise is obtained. In a Ti-sapphire mode-locked laser, the jitter is theoretically estimated, and the result is well consistent with the experimental value.     

自锁模固体激光器中的腔色散不共轴性

计算布儒斯特角切割的增益介质的色散引起的不同波长光波在谐振腔的振荡轴的不共轴性，其结果表明腔色散不共轴性的横向效应不亚于自聚焦效应，它对自销模脉冲的产生和压缩有严重的影响。     

飞秒锁模固态激光器中放大的自发辐射导致的时基抖动

基于飞秒锁模固态激光系统,推导了激光脉冲的振幅、脉宽的倒数、啁啾、频率、中心位置和位相的运动方程.在低的白噪声的假设下,估算了含啁啾的钛宝石激光器中由放大的自发辐射引起的时基抖动.结果表明:对于一台脉冲轮廓为sech²(1763t/τ)的确定的锁模固态激光系统,时基抖动近似为净群速延迟色散(GDD)的线性函数,且随着GDD的增加而变大;然而,即便在GDD被完全补偿的情况下,时基抖动也不会是零 关键词： 时基抖时 放大的自发辐射 飞秒锁模固态激光系统     

Attosecond‐precision ultrafast photonics

We review our recent progress toward attosecond‐precision ultrafast photonics based on ultra‐low timing jitter optical pulse trains from mode‐locked lasers. In femtosecond mode‐locked lasers, the concentration of a large number of photons in an extremely short pulse duration enables the scaling of timing jitter into the attosecond regime. To characterize such jitter levels, we developed new attosecond‐resolution measurement techniques and show that standard fiber lasers can achieve sub‐fs high‐frequency jitter. By leveraging the ultra‐low jitter of free‐running mode‐locked lasers, we pursued high‐precision optical‐optical and optical‐microwave synchronization techniques. Optical signals spanning 1.5 octaves were synthesized by attosecond‐precision timing and phase synchronization of two independent mode‐locked lasers. High‐stability microwave signals were also synthesized from mode‐locked lasers with drift‐free sub‐10‐fs precision. We further demonstrated the attosecond‐precision distribution of optical pulse trains to remote locations via timing‐stabilized fiber links. Finally, the application of optical pulse trains for high‐resolution sampling and analog‐to‐digital conversion is discussed.     

一种新型可调谐锁模光纤激光器

利用法布里-珀罗腔的激光二极管作为调制器件，实现环形腔光纤激光器的主动锁模。并利用法布里-珀罗腔的激光二极管的多纵模特性，把激光二极管当作一梳状滤波器，通过偏振控制器来调整入射到激光二极管内光的偏振态，同时均衡腔内增益，得到波长大范围可调谐的锁模激光，其脉冲宽度约为48ps，脉冲重复速率2GHz。     

Reduction of time jitter in a passively Q-switched and mode-locked ruby laser by a double-pulse technique

The onset of the picosecond pulse train in a passively Q-switched and modelocked solid state laser occurs with a considerable time jitter. A method has been devised which employs double-pulse pumping of the laser rod as a means to substantially reduce this jitter. With the ruby laser used, a reduction of more than twenty times, from 35 μsec to 1.5 μsec, was observed without altering the characteristics of the mode-locked pulse train or flash-lamp life. The synchronization of auxiliary equipment is thus made possible.     

High Quality Factor Q and Low Timing Jitter from MLLD Using Optical Injection

采用１０ＧＨｚ基准时钟光和１０Ｇｂｉｔ／ｓ的数据脉冲信号光注入到锁模激光二极管，降低了周期抖动，当注入功率为－５ｄＢｍ，在基准时钟光波长等于锁模激光二极管的光波长时，获得的最小抖动为０．２５ｐｓ，采用混合锁模激光二极管，在注入功率为＋２７ｄＢｍ时，其Ｑ值达３０００．     

Timing jitter reduction of optical pulse source using unpumped erbium doped fiber

A technique to enhance the stability of optical pulse source has been proposed that employs a specific length of unpumped erbium doped fiber. Two types of pulse sources are used one after the other, one of them is a 10 GHz mode locked laser and the other is a gain switched DFB laser diode with the repetition rate of 2 GHz. A 3-m erbium doped fiber is consolidated outside the cavity of the pulse sources so as to form strong standing waves, resulting into enhanced spatial hole burning effect. As a result, the phase noise of the pulse source is suppressed, whereas the possible undesired changes in the attributes of the pulse source are also nullified because we have designed the setup outside the cavity of the pulse source. Consequently, the timing jitter of the pulse source is reduced significantly.     

用光脉冲注入从锁模激光二极管再生低抖动高Q值光时钟

采用１０ＧＨＺ基准时钟光和１０Ｇｂｉｔ／ｓ的数据脉冲信号光注入到锁模激光二极管，降低了周期抖动，当注入功率为－５ｄＢｍ，在基准时钟光波长等于锁模激光二极管的光波长时，获得的最小抖动为０．２５ｐｓ，采用给锁模激光二极管，在注入功率为＋２７ｄＢｍ时，其Ｑ值达３０００。     

自调Q自锁模固体激光器

利用被动锁模激光器的锁模原理,结合自锁模固体激光器中等效快可饱和吸收体的特性,讨论了控制运转状态的自锁模动力学方程和速率方程,给出了自调Q自锁模的条件,以及自调Q周期与激光器结构和运转参数的关系,所得结论与实验结果有很好的一致性。     

7.13 W全固态1 319 nm宏微脉冲激光器

 研制了一台高效率全固态平均功率7.13 W的1 319 nm宏微脉冲激光器。激光器采用热稳Z形折叠腔,增益模块采用自行研制的准连续15个二极管芯片环形泵浦的Nd:YAG模块,采用主动声光锁模器作为锁模元件,并在腔内插入倍频KTP晶体对激光器的输出尖峰进行抑制。为了获得稳定的锁模状态,对激光器腔长进行了精确设计和调节。当激光器腔长与锁模器驱动频率匹配时,获取了宏脉冲重复频率400 Hz、脉宽约190 μs,微脉冲重复频率95.6 MHz、脉宽小于1.0 ns的1 319 nm激光脉冲。     

大色散稳定腔长的光纤锁模激光器的锁模特性研究

报道了一种新型的采用大色散腔结构的光纤锁模激光器,它可以有效地克服激光器腔长抖动对锁模的不良影响,同时,实验中发现,该结构对超模噪声也有很好的抑制作用。完成了大色散控制,电光调制器调制的,稳定的光纤锁模激光器实验,得到形状为sech^2的光脉冲输出,脉冲宽度为7.6ps,脉冲带宽积为0．335。     

All-Fiber Self-Injection Seeding for Optical Timing Jitter Reduction in a Chirp Compensated Gain-Switched DFB Laser

We demonstrate an original all-fiber self-injection seeding technique based on a noninterferometric reflector for the optical timing jitter reduction in a chirp compen sated gain-switched Distributed FeedBack (DFB) laser. Two experiments, at 2.5 and 5 GHz, show standard deviations of the optical timing jitter of 0.28 ps and a reduction factor of 17 in the best case. The self-injection seeding sensitivity to polarization effects and to modulating frequency changes was measured in terms of standard deviation. A final experiment at 10 GHz, with no external feedback, shows an optical timing jitter down to 0.4 ps due to a time dynamics of spontaneous emission fluctuations slower than the pulse period.     

增益介质的色散对锁模激光器输出脉宽和啁啾的影响

利用时间域内各光学元件的传播矩阵,在考虑了增益介质的色散后,对锁模激光器输出的脉宽和啁啾做了理论方面的推导,并做了相关的数值模拟,结果表明:当不考虑增益介质的色散时,其输出脉宽啁啾值为零;而考虑了增益介质的色散后,啁啾值随色散值的增加先增加而后降低,且存在一个最大值,脉宽随色散值的增加而增加.     

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.     

环形腔自锁模掺钛蓝宝石激光器

实现了环形腔掺钛蓝宝石激光器的自锁模运转。在双向同时锁模时获得脉宽为３６ｆｓ的锁模脉冲；在单向锁模时得到脉宽为３２ｆｓ的锁模脉冲。并对激光器的运转特性进行了分析。     

啁啾匹配和同步抖动对光参量啁啾脉冲放大的影响

 通过研究光参量啁啾脉冲放大过程转换效率随泵浦光啁啾参数的变化,以及信号光和泵浦光波长的对应关系,确立了信号光和泵浦光同步时实现线性啁啾匹配的方法。以磷酸二氢钾作为非线性晶体,研究了信号光和泵浦光之间的线性啁啾匹配和时间同步抖动对光参量啁啾脉冲放大后信号光脉冲波形和转换效率的影响。结果表明：在时间同步的情况下,线性啁啾匹配时的信号光脉冲波形很对称,转换效率也较高;在同步抖动程度一定的情况下,不同泵浦光啁啾参数时,信号光的增益及放大后的脉冲波形差异较大;在线性啁啾匹配程度一定时,信号光和泵浦光时间同步抖动越严重,放大信号光的脉冲波形变化越大,信号光增益越小,且转换效率也越低。     

一种用于荧光皮秒时间分辨光谱的测试系统

本文详细描述了一种由氩离子锁模激光器、样品池、分光系统及微微秒条纹相机构成的用于测试低强度荧光微微秒时间分辨光谱的系统。给出了典型样品的测试结果:时间分辨率为10ps,光谱范围为500Å—800Å。最后对测量结果进行了分析讨论。     

根据激光单脉冲能量空间分布测量激光横模结构的方法

针对脉冲激光器,提出了一种根据激光单脉冲能量空间分布测量激光横模结构的方法,构造了相应算法,并通过理论和实验验证了该方法.通过对调Q二极管泵浦固体激光器的调Q过程进行数值模拟,计算出单脉冲能量空间分布曲线和各阶横模比例,同时根据单脉冲能量空间分布曲线上一些离散点计算出各阶横模比例,且与调Q过程数值模拟的直接计算结果相等.同时在实验中根据测量出的单脉冲能量相对值,计算出各阶横模比例,拟合出腔外不同距离处的单脉冲能量空间分布曲线.对腔外不同距离处单脉冲能量相对值和相应拟合曲线进行比较,发现测量值和拟合曲线吻合.     

Measurement of mode-locked laser timing jitter by use of phase-encoded optical sampling

The phase-noise characteristics of a harmonically mode-locked fiber laser are investigated with a new measurement technique called phase-encoded optical sampling. A polarization-maintaining ring laser is mode locked by use of the short-pulse electrical output of a resonant-tunneling diode oscillator, enabling it to produce 30-ps pulses at a 208-MHz repetition rate. The interferometric phase-encoded sampling technique provides 60-dB suppression of amplitude-jitter noise and allows supermode phase noise to be observed and quantified. The white-noise pulse-to-pulse timing jitter and the rms supermode timing jitter of the laser are measured to be less than 50 and 70 fs, respectively.