300W线偏振飞秒全光纤啁啾脉冲放大系统北大核心CSCD

报道了高平均功率的线偏振啁啾脉冲放大系统。该系统包括全光纤结构的多级放大器以及透射光栅脉冲压缩器。压缩前,实现了近衍射极限光束输出,平均功率425 W,光光效率81%,消光比约13dB;压缩后,获得了平均功率300 W、脉宽315fs、峰值功率12 MW的激光脉冲,为目前报道的最高平均功率的线偏振光纤啁啾脉冲放大系统。     

基于MOPA结构与高能量种子源的高功率皮秒掺铥光纤放大器

以单脉冲能量更高的孤子激光器为种子源,通过主振荡放大技术,获得了2 μm波段的高功率、皮秒脉冲激光器.该种子源是一个被动锁模的光纤激光器,通过优化、管理激光器谐振腔内的色散,获得了脉冲宽度为50 ps、重复频率为55.6 MHz、谱宽约为21 nm的高能量孤子脉冲输出.利用单模光纤在2μm波段的负啁啾色散特性,在进行功率放大之前将作为种子源的激光脉冲宽度展宽至600 ps.最后,经过两级放大之后,获得平均功率约23 W、脉宽为660 ps的激光输出.利用光栅对,对放大后的激光脉冲进行压缩,经测试压缩后的脉冲宽度约为0.9 ps.     

高功率全光纤啁啾脉冲放大激光系统

采用基于非线性偏振旋转原理的光纤被动锁模激光器作为主振荡器。输出信号脉冲的重复频率为30MHz,脉冲半高全宽为265fs。信号脉冲通过全光纤啁啾脉冲激光放大系统展宽至100ps后,经过1级芯径10μm的光纤预放大器和1级芯径50μm的光纤功率放大器将脉冲平均功率放大至10W,斜率效率41.5%。输出脉冲经光栅压缩器将脉宽压缩至594fs。     

基于MOPA结构与高能量种子源的高功率皮秒掺铥光纤放大器（英文）

以单脉冲能量更高的孤子激光器为种子源,通过主振荡放大技术,获得了2μm波段的高功率、皮秒脉冲激光器.该种子源是一个被动锁模的光纤激光器,通过优化、管理激光器谐振腔内的色散,获得了脉冲宽度为50ps、重复频率为55.6 MHz、谱宽约为21nm的高能量孤子脉冲输出.利用单模光纤在2μm波段的负啁啾色散特性,在进行功率放大之前将作为种子源的激光脉冲宽度展宽至600ps.最后,经过两级放大之后,获得平均功率约23 W、脉宽为660ps的激光输出.利用光栅对,对放大后的激光脉冲进行压缩,经测试压缩后的脉冲宽度约为0.9ps.     

光子晶体光纤飞秒激光非线性放大系统的耦合动力学过程研究

构建了掺镱大模场面积单偏振光子晶体光纤飞秒激光非线性放大系统. 讨论了腔内净色散量和抽运功率对振荡级输出参数的影响和振荡级参数对放大级输出参数的影响. 在本实验条件下, 当腔内净色散量取较大负色散时, 振荡级直接输出的脉冲更宽, 且携带更少的啁啾. 当振荡级抽运4.53 W时, 选择最接近变换极限的脉冲作为种子脉冲, 放大级在60 W抽运时输出压缩后无基底的短脉冲, 宽度为45.7 fs, 平均功率28 W. 振荡级抽运功率增加到5.08 W, 放大级抽运70 W时, 获得最高输出功率34.5 W, 对应脉宽53.5 fs.     

采用光谱展宽技术的钛宝石飞秒激光放大器

报道了飞秒激光啁啾脉冲放大器中的激光脉冲光谱展宽技术，实验中使用了几种光谱展宽元件，结果表明使用激光光谱展宽元件能有效地将飞秒激光脉冲 光谱展宽，抑制了飞秒激光放大器中常见的激光脉冲光谱增益窄化现象，从飞秒放大系统的振荡级输出28fs种子脉冲，放大后得到了重复频率为10Hz、峰值功率为1．6TW、脉冲宽度37．5fs的超短强飞秒激光脉冲 。     

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。     

钕玻璃啁啾脉冲放大器产生百焦耳亚皮秒脉冲

以钕玻璃为增益介质研制了高能啁啾脉冲激光放大器系统,实验演示输出啁啾脉冲能量在百焦耳量级时,光谱宽度保持在4—6 nm.最大能量168 J,相应谱宽5.5 nm,中心波长1054 nm.压缩脉冲宽度最短710 fs. 关键词： 啁啾脉冲放大 钕玻璃 高能拍瓦     

一种全光纤啁啾脉冲放大系统设计

提出了一种全光纤啁啾脉冲放大系统,在理论分析的基础上,利用分步傅里叶法,通过求解非线性薛定谔方程,对由组合A(1m的DCF+2m的EDF+3.08m的SMF)与组合B(1m的DCF+2m的LMA-EDF+0.61m的SMF)分别构成的两个全光纤啁啾脉冲放大系统进行分段数值模拟,结果发现,将重复频率为100MHz、峰值功率为33.3 W、脉宽为300fs的种子脉冲经过组合A构成的放大系统后,变为重复频率为100 MHz、峰值功率为18 062.43 W、脉宽约为56fs的脉冲;而经过组合B构成的放大系统后,种子脉冲则变为重复频率为100 MHz、峰值功率为31 022.24 W、脉宽约为50fs的脉冲。     

全光纤高能量飞秒脉冲激光放大系统

研究了一种全光纤飞秒脉冲放大系统。其采用非线性放大环形镜结构的谐振腔输出宽光谱种子光,通过光纤啁啾脉冲放大技术抑制功率放大过程中的非线性累积;主放大部分结合双包层光纤与大模场光子晶体光纤熔接技术,输出中心波长1030nm,平均功率16.9W的高质量皮秒脉冲,经空间光栅对补偿色散后脉冲宽度324fs,单脉冲能量12.2μJ,峰值功率约26.4MW。该放大系统采用保偏光纤特种熔接技术实现全光纤化,相较于空间耦合放大具有光路结构简单,环境稳定性高等特点,有望推动高能量飞秒光纤激光工业化进程,提升其在复杂使用环境的适应性。     

高稳定性、高质量脉冲压缩飞秒光纤激光系统研究

报道了一款用于眼科手术的高稳定性、高质量脉冲压缩飞秒光纤主振荡功率放大系统. 振荡器采用混合腔方式增加了光纤双折射, 改善了非线性偏振旋转锁模在低重复频率下无法自启动的缺点, 提高了飞秒光纤激光器自启动锁模的稳定性. 研究了脉冲预啁啾与飞秒脉冲压缩质量的关系, 通过实验证明了光纤放大器的入射脉冲保持负的预啁啾状态可以得到最好的脉冲压缩结果. 实验最终实现了满足自启动锁模条件的重复频率19.4 MHz、平均功率1.2 W、脉冲宽度183 fs的激光脉冲, 目前这台激光器是国内首台具有自主知识产权并应用于动物角膜实验的飞秒光纤激光器.     

High-peak-power femtosecond pulse compression with polarization-maintaining ytterbium-doped fiber amplification

We report the generation of 140 fs pulses with a peak power of up to 270 kW using a fiber pulse source based on a polarization-maintaining ytterbium-doped fiber amplifier and a semiconductor saturable absorber mirror mode-locked fiber laser seed. The seed laser pulses were amplified and chirped in the fiber amplifier and subsequently compressed in an external transmission grating pair. The use of a polarization-maintaining amplifier addresses nonlinear polarization-induced limitations to the obtainable compressed pulse duration and quality that can arise if isotropic fiber amplification is used. Numerical simulations of the system support the experimental measurements and also confirm the role of fiber dispersion in obtaining high-quality compressed pulses.     

Mode-locked all-fiber laser with high stability based on cobalt oxyfluoride

Recent years have witnessed the exploration of fiber laser technology focused on numerous pivotal optoelectronic applications from laser processing and remote sensing to optical communication. Here, using cobalt oxyfluoride(Co OF) as the nonlinear material, a 156 fs mode-locked fiber laser with strong stability is obtained. The rapid thermal annealing technique is used to fabricate the Co OF, which is subsequently transferred to the tapered region of the microfiber to form the effective pulse modulation device. Co OF interacts with the pulsed laser through the evanescent field to realize the intracavity pulse shaping, and then the stable mode-locked pulse is obtained. The mode-locked operation is maintained with the pulse duration of 156 fs and repetition rate of 49 MHz. In addition, the signal-to-noise ratio is about 90 d B. Those experimental results confirm the attractive nonlinear optical properties of Co OF and lay a foundation for the ultrafast application of lowdimensional transition metal oxides.     

位于第三近红外窗口的平坦光纤超连续谱产生

报道了一种基于非线性偏振旋转效应的被动锁模光纤激光器。采用980 nm分布式反馈激光器作为泵浦源,0.5 m长的高掺杂掺铒光纤作为增益介质。实现了脉冲宽度为822 fs的传统孤子锁模脉冲,输出脉冲的平均功率为2.8 mW,信噪比为55.8 dB。通过微调腔内的偏振控制器,实现了传统孤子脉冲和孤子分子脉冲间的切换,孤子分子的脉冲宽度为312 fs,信噪比为53.86 dB。孤子分子脉冲经掺铒光纤放大器放大后泵浦一段57 m长的高非线性光纤,产生了位于第三近红外窗口（1600 nm～1870 nm）的超连续谱,其20 dB谱宽为355.8 nm。     

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。     

Multibeam second-harmonic generation by spatiotemporal shaping of femtosecond pulses

We present a technique for efficient generation of the second-harmonic signal at several points of a nonlinear crystal simultaneously. Multispot operation is performed by using a diffractive optical element that splits the near-infrared light of a mode-locked Ti:sapphire laser into an arbitrary array of beams that are transformed into an array of foci at the nonlinear crystal. We show that, for pulse temporal durations under 100 fs, spatiotemporal shaping of the pulse is mandatory to overcome chromatic dispersion effects that spread both in space and time the foci showing a reduced peak intensity that prevents nonlinear phenomena. We experimentally demonstrate arbitrary irradiance patterns for the second-harmonic signal consisting of more than 100 spots with a multipass amplifier delivering 28 fs, 0.8 mJ pulses at 1 kHz repetition rate.     

Ultralow-jitter passive timing stabilization of a mode-locked Er-doped fiber laser by injection of an optical pulse train

The pulse timing of a mode-locked Er-doped fiber laser was stabilized to a reference pulse train from a Cr:forsterite mode-locked laser by all-optical passive synchronization scheme. The reference pulses were injected into a ring cavity of the fiber laser by using a 1.3-1.5 mum wavelength-division multiplexer. The spectral shift induced by cross-phase modulation between copropagating two-color pulses realizes self-synchronization due to intracavity group-delay dispersion. The rms integration of timing jitter between the fiber laser pulse and the reference pulse was 3.7 fs in a Fourier frequency range from 1 Hz to 100 kHz.     

利用非线性脉冲预整形实现脉冲快速自相似放大

报道了一种通过预先对信号光脉冲非线性整形, 进而在光纤放大器中实现自相似演化的方法. 利用透射光栅对和普通单模光纤组成被动脉冲整形装置, 预先优化脉冲的时域宽度和光谱质量, 使脉冲在光纤放大器中快速演化到自相似子. 研究中首先通过数值模拟对比, 说明了非线性整形对脉冲实现快速自相似放大的关键作用, 提高了放大器输出脉冲质量, 减小了去啁啾脉冲宽度. 实验中, 通过优化非线性整形输出, 在2.2 m 长的掺Yb³⁺光纤中, 在一定抽运功率范围内均实现了脉冲自相似放大, 去啁啾后得到脉冲宽度60 fs 的变换极限脉冲输出. 这种非线性脉冲预整形方法有效减小了 自相似演化所需光纤长度, 同时降低了自相似放大对种子源质量的要求, 首次将全正色散光纤锁模激光器成功用于自相似放大, 促进了当前自相似放大系统的全光纤化. 关键词： 非线性整形 光纤放大器 自相似放大 飞秒激光     

Mode-locked fiber laser based on an attenuation-imbalanced nonlinear optical loop mirror

We propose a mode-locked figure-eight fiber laser by utilizing an attenuation-imbalanced nonlinear optical loop mirror (AI-NOLM) for the first time. Stable self-starting passively mode-locked pulses as short as 296 fs are obtained. We have also confirmed that the pulse width of the laser can be varied by changing the amount of attenuation in the AI-NOLM.