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Towards tapered-fiber-based all-fiberized high power narrow linewidth fiber laser

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Science China(Technological Sciences) 2018年第7期61卷 971-981页

作者： HUANG Long ZHOU ZiChao SHI Chen tao rumao MA PengFei WANG XiaoLin ZHOU Pu College of Optoelectronic Science and Engineering National University of Defense TechnologyChangsha 410073China Hunan Provincial Collaborative Innovation Center of High Power Fiber Laser Changsha 410073China

Yb-doped fiber laser(YDFL) is a promising kind of laser source due to high efficiency, excellent beam quality, robust configuration, diverse applications and so on. The progress of large-mode-area double cladding active fiber and high power laser diodes have been continuously promoting the power scaling of the YDFLs. However, the further power scaling is blocked by some physic issues including nonlinear effect, thermal-induced mode instability(MI), optical damage and so forth. So, newlydesigned fibers with special structures are invented to address or relieve these limitations. The tapered fiber, which has changed mode area along its longitudinal direction, has been demonstrated to benefit suppressing the nonlinear effect, especially the stimulated Brillouin scattering(SBS) effect. In this paper, we will review the previous work done to explore the advantages of the tapered fiber for high power output, and then for the first time to our knowledge, demonstrate an all-fiberized high power narrow linewidth fiber laser based on a homemade tapered Yb-doped fiber(T-YDF). As a result, an output power of 260 W with a narrow linewidth of ~2 GHz is obtained, with SBS effectively suppressed owing to gradually increased mode area of the T-YDF as well as continuously changed Brillouin frequency shift dependent on the core diameter. Further power scaling is limited by MI, and the features of MI are studied in detail. It is pointed out that, the MI seems the primary and durative limitation factor of the tapered fiber amplifier for high power narrow linewidth output due to the gradually increased effective numerical aperture(NA) and the excitation of the high-order modes, even although it has the advantage to reduce other nonlinear effects. At last,worthwhile discussion about the optimization of the T-YDF and the whole fiber laser system for both SBS and MI suppression is conducted based on the previous and our results. It is concluded that the small diameter at the small-diameter

关键词： tapered Yb-doped fiber high power narrow linewidth stimulated Brillouin scattering mode instability

大规模激光相干合成主动相位控制技术研究进展

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强激光与粒子束 2024年第6期36卷 1-23页

作者：周宏冰张昊宇李敏冯曦谢亮华刘玙楚秋慧闫玥芳陶汝茂林宏奂王建军颜立新景峰中国工程物理研究院激光聚变研究中心四川绵阳621900 清华大学加速器实验室北京100084

大规模激光相干合成是突破单口径激光特性极限、获得超高峰值/平均功率、超大脉冲能量、超高空/谱亮度等极端特性激光的有效技术路径之一,而大规模激光相干合成的关键是主动相位控制。主动相位控制技术可以对各路光束相位进行主动控制,... 详细信息

大规模激光相干合成是突破单口径激光特性极限、获得超高峰值/平均功率、超大脉冲能量、超高空/谱亮度等极端特性激光的有效技术路径之一,而大规模激光相干合成的关键是主动相位控制。主动相位控制技术可以对各路光束相位进行主动控制,补偿相位噪声引起的相干特性退化、合成效率下降,获得高品质的合成激光。自相干合成技术提出以来,研究人员开发了多种主动相位控制方法用于相干合成相位校正,其中适用于大规模激光相干合成的主动相位控制方法也得到了飞速发展。系统梳理了大规模激光相干合成的主动相位控制方法,深入分析了不同方法的原理、特点、适用场景和扩展能力,介绍了不同方法取得的相干合成研究最新进展及标志性成果,报道了19通道闭环上升时间仅6μs的相干合成锁相控制突破性结果,最后总结和展望了主动相位控制方法的发展趋势。

关键词：相干合成主动相位控制多抖动随机并行梯度下降机器学习

1.3 kW monolithic linearly polarized single-mode master oscillator power amplifier and strategies for mitigating mode instabilities

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Photonics Research 2015年第3期3卷 86-93页

作者： rumao tao Pengfei Ma Xiaolin Wang Pu Zhou Zejin Liu College of Optoelectric Science and Engineering National University of Defense Technology

We report on the high-power amplification of a 1064 nm linearly polarized laser in an all-fiber polarizationmaintained master oscillator power amplifier,which can operate at an output power level of 1.3 *** beam quality(M^2) was measured to be <1.2 at full power *** polarization extinction rate of the fiber amplifier was measured to be above 94% before mode instabilities(MIs) set in,which reduced to about 90% after the onset of *** power scaling capability of strategies for suppressing MI is analyzed based on a semianalytical model,the theoretical results of which agree with the experimental *** shows that mitigating MI by coiling the gain fiber is an effective and practical method in standard double-cladding large mode area fiber,and,by tight coiling of the gain fiber to the radius of 5.5 cm,the MI threshold can be increased to three times higher than that without coiling or loose *** studies have been carried out to verify the idea,which has proved that MI was suppressed successfully in the amplifier by proper coiling.

关键词： mode kW monolithic linearly polarized single-mode master oscillator power amplifier and strategies for mitigating mode instabilities MI

Propagation of high-power fiber laser with high-order-mode content

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Photonics Research 2015年第4期3卷 192-199页

作者： rumao tao Long Huang Pu Zhou Lei Si Zejin Liu College of Optoelectric Science and Engineering National University of Defense Technology

Propagation properties of high-power fiber laser with high-order-mode(HOM) content are studied numerically for the first time to the best of our knowledge. The effect of HOM on the propagation property is evaluated by the power in the bucket(PIB) metric. It is shown that PIB is mainly dependent on HOM content rather than the relative phase between the fundamental mode and HOM. The PIB in vacuum is more than 80% when the power fraction of the HOM is controlled to be less than 50% at 5 km. The relative phase has an impact on the peak intensity position and concentration of the far-field intensity distribution. If an adaptive optics system is used to correct the peak intensity deviation, the results indicate that there exists a maximal value of PIB as relative phase increases. Such effect is weakened when propagating in turbulence. Compared to the laser beams without HOM, laser beams with HOM content are less influenced by the turbulence and can reduce average intensity fluctuation. The results may be useful in the design of a high-power fiber laser system.

关键词： mode Propagation of high-power fiber laser with high-order-mode content PIB high

Kilowatt high average power narrow-linewidth nanosecond all-fiber laser

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High Power Laser Science and Engineering 2014年第1期2卷 45-48页

作者： Rongtao Su Pu Zhou Xiaolin Wang rumao tao Xiaojun Xu College of Optoelectronic Science and Engineering National University of Defense Technology

A high power narrow-linewidth nanosecond all-fiber laser based on the master oscillator power amplifier(MOPA)configuration is demonstrated. A pulsed seed with high repetition rate of 10 MHz was generated by modulating a continuous-wave(CW) single-frequency fiber laser at ～1064 nm by using an electro-optic intensity modulator(EOIM).After multi-stage cascaded power amplification, the average power was boosted to be kilowatt level. The pulses from the main amplifier had a pulse width of ～3 ns and an average/peak power of 913 W/28.6 kW. Further power scaling of the pulses was limited by stimulated Raman scattering(SRS) for the moment, method for SRS suppression and further power scaling was briefly discussed.

关键词： fiber laser nanosecond pulsed laser narrow linewidth stimulated Raman scattering

Coherent beam combination of fiber lasers with a strongly confined tapered self-imaging waveguide:theoretical modeling and simulation

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Photonics Research 2013年第4期1卷 186-196页

作者： rumao tao Xiaolin Wang Hu Xiao Pu Zhou Lei Si College of Optoelectric Science and Engineering National University of Defense TechnologyChangshaHunan 410073China

Coherent beam combination(CBC)of fiber lasers based on self-imaging properties of a strongly confined tapered waveguide(SCTW)is studied *** formulas are derived for the positions,amplitudes,and phases of the N self-images at the output of a SCTW,which are important for quantitative analysis of waveguidebased *** formulas are verified with numerical examples by a finite difference beam propagation method(FDBPM)and the errors of the analytical expressions are *** study shows that the analytical formulas agree well with the FDBPM simulation results when the taper angle is less than 1.4°and the phase distortion is less thanλ∕*** relative errors increase as the taper angle *** on the theoretical model and the FDBPM,we simulated the CBC of fiber laser array and compared the CBC based on the tapered waveguide with that based on the nontapered *** effects of input beam number,aperture fill factor,and taper angle on the combination performance have been *** study reveals that a beam which has near-diffraction limited beam quality(M2≤1.41)and a single beam without side lobe in the far field can be achieved with tapered-waveguide-based *** is shown that beam quality depends on input beam number,aperture fill factor,and taper *** exists a best fill factor which will increase as input beam number *** tolerance of the system on the fill factor and the taper angle is studied,which is 0.45

关键词： waveguide fiber beam

自研(1+1)分布式侧面泵浦光纤实现20 kW激光输出

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光学学报 2024年第9期44卷 318-321页

作者：李峰云刘念张春代江云黄值河曹涧秋高聪陈艺黄伶俐楚秋慧张昊宇陶汝茂史仪赵龙彪林宏奂王建军王泽锋景峰中国工程物理研究院激光聚变研究中心四川绵阳621900 国防科技大学前沿交叉学科学院湖南长沙410073 国防科技大学南湖之光实验室湖南长沙410073 南京理工大学电子工程与光电技术学院江苏南京210094

基于改进的化学气相沉积预制棒制备技术和多光纤并束拉丝光纤拉制工艺,成功制备了(1+1)型分布式侧面泵浦光纤,其中信号纤芯/包层尺寸为60/300μm,泵浦纤芯尺寸为310μm。通过主振荡功率放大结构搭建反向泵浦放大系统,以1018 nm激光器为... 详细信息

基于改进的化学气相沉积预制棒制备技术和多光纤并束拉丝光纤拉制工艺,成功制备了(1+1)型分布式侧面泵浦光纤,其中信号纤芯/包层尺寸为60/300μm,泵浦纤芯尺寸为310μm。通过主振荡功率放大结构搭建反向泵浦放大系统,以1018 nm激光器为级联泵浦源,该光纤激光器最终实现了20.13 kW的最高功率输出,经过拟合后的斜率效率为82.3%,由泵浦纤反向端输出的残余泵浦比例的最大值为6%,信号光受激拉曼散射抑制比达到37.65 dB。在测试中,光纤所有部位均表现出优异的热负载性能,这是首次通过(1+1)型分布式侧面泵浦方式实现了20 kW的单根光纤输出功率。

关键词：光纤光学高功率光纤激光器分布式侧面泵浦残余泵浦受激拉曼散射

Comprehensive investigation on producing high-power orbital angular momentum beams by coherent combining technology

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High Power Laser Science and Engineering 2019年第2期7卷 88-96页

作者： Dong Zhi Tianyue Hou Pengfei Ma Yanxing Ma Pu Zhou rumao tao Xiaolin Wang Lei Si College of Advanced Interdisciplinary Studies.National University cf Defense Technology Changsha 410073China Hypervelocity Aerodynamics Institute China Aerodynamics Research and Development CenterMianyang 621000.China

High-power orbital angular momentum(OAM)beams have distinct advantages in improving capacity and data receiving for free-space optical communication systems at long *** the coherent combination of a beam array technique and helical phase approximation by a piston phase array,we have proposed a generating system for a novel high-power beam carrying OAM,which could overcome the power limitations of a common vortex phase modulator and a single *** characteristics of this generating method and the orthogonality of the generated OAM beams with different eigenstates have been theoretically analyzed and *** a high-power OAM beam produced by coherent beam combination(CBC)of a six-element hexagonal fiber amplifier array has been experimentally *** show that the CBC technique utilized to control the piston phase differences among the array beams has a high efficiency of 96.3%.On the premise of CBC,we have obtained novel vortex beams carrying OAM of±1 by applying an additional piston phase array modulation on the corresponding beam *** experimental results agree approximately with the theoretical *** work could be beneficial to areas that need high-power OAM beams,such as ultra-long distance free-space optical communications,biomedical treatments,and powerful trapping and manipulation under deep potential wells.

关键词： orbital angular momentum beams coherent beam combination

Monolithic high-average-power linearly polarized nanosecond pulsed fiber laser with near-diffraction-limited beam quality

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High Power Laser Science and Engineering 2018年第3期6卷 28-35页

作者： Long Huang Pengfei Ma Daren Meng Lei Li rumao tao Rongtao Su Yanxing Ma Pu Zhou College of Optoelectronic Science and Engineering National University of Defense Technology Changsha 410073 China Hunan Provincial Collaborative Innovation Center of High Power Fiber Laser Changsha 410073 China

An all-fiberized high-average-power narrow linewidth ns pulsed laser with linear polarization is demonstrated. The laser system utilizes a typical master oscillator power amplifier(MOPA) configuration. The stimulated Brillouin scattering(SBS) is effectively suppressed due to the short fiber length and large mode area in the main amplifier, combined with the narrow pulse duration smaller than the phonon lifetime of SBS effect. A maximal output power of 466 W is obtained with a narrow linewidth of ～203.6 MHz, and the corresponding slope efficiency is ～80.3%. The pulse duration is condensed to be ～4 ns after the amplification, corresponding to the peak power of 8.8 kW and the pulse energy of 46.6 μJ. Neardiffraction-limited beam quality with an M2 factor of 1.32 is obtained at the output power of 442 W and the mode instability(MI) is observed at the maximal output power. To the best of our knowledge, this is the highest average output power of the all-fiberized narrow linewidth ns pulsed fiber laser with linear polarization and high beam quality, which is a promising source for the nonlinear frequency conversion, laser lidar, and so on.

关键词： all-fiber high power linear polarization mode instability narrow linewidth stimulated Brillouin scattering