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高平均功率(>500 W)、大脉冲能量(>1 mJ)飞秒光纤激光对包括阿秒光学在内的众多科研领域极为重要. 受限于增益光纤较小的模场面积, 多种非线性效应将从单根增益光纤放大产生的飞秒脉冲的能量限制在百微焦量级. 平均功率和脉冲能量的进一步提升需要使用相干合成技术, 将多路光纤的输出合成为一束. 本文搭建了一套基于填充孔径相干合成的高功率大能量超快光纤激光系统, 采用商用掺镱棒状光纤并利用随机并行梯度下降法实现四路放大器之间的相位锁定. 在重复频率为1 MHz时, 该相干合成系统输出平均功率为753 W, 经过光栅对压缩后的平均功率为672 W, 脉冲宽度为242 fs, 对应的脉冲能量为0.67 mJ, 系统具备良好的稳定性. 降低重复频率至500 kHz, 该系统输出压缩后的脉冲平均功率为534 W, 脉冲宽度为247 fs, 对应脉冲能量可达1.07 mJ. 脉冲的平均功率和能量均可通过增加合成路数进一步提升, 通过添加已着手研发的延迟和指向锁定系统, 有望通过八路相干合成实现平均功率超过1 kW、脉冲能量超过2 mJ的飞秒脉冲输出.
Ultrafast fiber laser sources with mJ-level pulse energy and kilo-watt average power are of particular importance for various science fields such as attosecond lasers. Currently, several large-scale facilities for attosecond lasers, including ELI-ALPS in Europe, SECUF in China, NeXUS in America and ALFA in Japan are under construction. High-performance femtosecond driven lasers are crucial for attosecond lasers and various ultrafast laser facilities. Fiber lasers have a large surface-to-volume ratio, which enables efficient cooling and is suitable for high average power amplification. However, due to small mode area of optical fibers, detrimental nonlinear optical effects such as self-phase modulation, four-wave mixing, and stimulated Raman scattering limit the peak power of pulse to hundreds of MW, corresponding to pulse energy of hundreds of μJ for femtosecond pulses in large mode area rod-type fibers. In addition, the average power of fiber lasers is limited by transverse mode instability, which reduces the stability and quality of beams above a certain threshold. In rod-type fibers, the threshold is about 250 W. Neither average power nor pulse energy emitted by single fiber meets the requirement for attosecond laser generation. The average power and pulse energy can be further scaled by coherent beam combination, which involves splitting pulses caused by an frontend laser and recombining them after amplification. It is essential for coherent beam combination to maintain the coherence of pulse replicas, which usually involves high speed photodiode detectors, piezo-driven mirrors, and other electronics forming a feedback system to actively control the phase of all replicas. We present a high-energy high-power ultrafast fiber laser system by using filled-aperture coherent combination of four ytterbium-doped rod-type fiber amplifiers. The phase control is achieved by using stochastic parallel gradient descent method. The frontend includes a passively mode-locked Yb-fiber oscillator, a stretcher, a pulse picker, and three fiber pre-amplifiers, which delivers 1 MHz stretched pulses centered at 1032 nm with 700 ps duration and 20 W average power. The pulse is split into four replicas by polarization beam-splitter and half-wave plate pairs, and the replicas pass through delay lines formed by piezo-driven mirrors before amplification. The pulse replicas are equally split and amplified to ensure the same accumulated nonlinear phase, and are combined by thin film polarizer and half-wave plate pairs. A small portion of the combined pulse is split and collected by a photodiode detector after being filtered spectrally and spatially, serving as a signal for controlling phase. The combined pulse is compressed by a compressor using a double-pass diffraction grating pair consisting of two 1739 l/mm gratings. At a repetition rate of 1 MHz, our four-channel Yb-fiber coherent beam combination system generates a combined average power value of 753 W and a combination efficiency of 87%. By utilizing an adjustable pulse stretcher and compressor, a 0.67 mJ, 242 fs near transform-limited pulse can be generated with a compressing efficiency of 89%. The compressed pulse is centered at 1032 nm, and the spectrum width is 8.8-nm. In the 30 min measurement, the root-mean-square of average power is less than 1% , while the residual phase error is less than λ/23, indicating excellent stability on different time scales. The beam quality factor of the 0.67 mJ compressed pulses is 1.17×1.11. At 500 kHz, we obtain pulses of 1.07 mJ and 247 fs with average power of 534 W, exhibiting similar efficiency, long-term stability, and beam quality. The residual phase error decreases below λ/29, indicating better short-term stability. Further scaling power and energy can be achieved by increasing the number of channels. By adding the delay stabilization system and pointing stabilization system, which are currently under development, an eight-channel CBC system can be used to generate 1 kW, 2 mJ pulses. In this work, we implement a four-channel coherent beam combining system based on the SPGD method, and obtain compressed pulses of 673 W, 673 µJ, and 242 fs at 1 MHz and 534 W, 1.07 mJ, and 247 fs at 500 kHz. Both power and energy can be further improved by increasing the channel number, and adding the delay stabilization system and pointing stabilization system which are under construction. By adding coherent pulse stacking amplification technology, the coherent beam combining system ought to generate pulse energy as high as 100 mJ, which constitutes the energy source for applications such as laser wake-field acceleration. [1] Chang G Q, Wei Z Y 2020 iScience 23 101101
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[2] Kirsche A, Gebhardt M, Klas R, Eisenbach L, Eschen W, Buldt J, Stark H, Rothhardt J, Limpert J 2023 Opt. Express 31 2744
Google Scholar
[3] Eidam T, Rothhardt J, Stutzki F, Jansen F, Hädrich S, Carstens H, Jauregui C, Limpert J, Tünnermann A 2011 Opt. Express 19 255
Google Scholar
[4] Eidam T, Wirth C, Jauregui C, Stutzki F, Jansen F, Otto H J, Schmidt O, Schreiber T, Limpert J, Tünnermann A 2011 Opt. Express 19 13218
Google Scholar
[5] Kienel M, Müller M, Klenke A, Limpert J, Tünnermann A 2016 Opt. Lett. 41 3343
Google Scholar
[6] Wan P, Yang L M, Liu J 2013 Opt. Express 21 29854
Google Scholar
[7] Stark H, Benner M, Buldt J, Klenke A, Limpert J 2023 Opt. Lett. 48 3007
Google Scholar
[8] Müller M, Aleshire C, Klenke A, Haddad E, Légaré F, Tünnermann A, Limpert J 2020 Opt. Lett. 45 3083
Google Scholar
[9] Jauregui C, Stihler C, Limpert J 2020 Adv. Opt. Photon. 12 429
Google Scholar
[10] Pedersen M E, Johansen M M, Olesen A S, Michieletto M, Gaponenko M, Maack M D 2022 Opt. Lett. 47 5172
Google Scholar
[11] 王栋梁, 史卓, 王井上, 吴洪悦, 张晓辉, 常国庆 2024 物理学报 73 134204
Google Scholar
Wang D L, Shi Z, Wang J S, Wu H Y, Zhang X H, Chang G Q 2024 Acta Phys. Sin. 73 134204
Google Scholar
[12] Peng S X, Wang Z H, Hu F L, Li Z Y, Zhang Q B, Lu P X 2024 Front. Optoelectron. 17 3
Google Scholar
[13] 王志浩, 彭双喜, 徐浩, 李政言, 张庆斌, 陆培祥 2024 光学学报 44 1732017
Google Scholar
Wang Z H, Peng S X, Xu H, Li Z Y, Zhang Q B, Lu P X 2024 Acta Opt. Sin. 44 1732017
Google Scholar
[14] 常洪祥, 靳凯凯, 张雨秋, 张嘉怡, 金坤, 李灿, 粟荣涛, 冷进勇, 周朴 2023 光学学报 43 1714008
Google Scholar
Chang H X, Jin K K, Zhang Y Q, Zhang J Y, Jin K, Li C, Su R T, Leng J Y, Zhou P 2023 Acta Opt. Sin. 43 1714008
Google Scholar
[15] 王涛, 李灿, 刘洋, 任博, 唐振强, 常洪祥, 谢戈辉, 郭琨, 吴坚, 许将明, 冷进勇, 马鹏飞, 粟荣涛, 李文雪, 周朴 2023 红外与激光工程 52 20220869
Google Scholar
Wang T, Li C, Liu Y, Ren B, Tang Z Q, Chang H X, Xie G H, Guo K, Wu J, Xu J M, Leng J Y, Ma P F, Su R T, Li W X, Zhou P 2023 Infrared Laser Eng. 52 20220869
Google Scholar
[16] Ren B, Chang H X, Li C, Wang T, Jin K K, Zhang J Y, Guo K, Su R T, Leng J Y, Zhou P 2024 Front. Optoelectron. 17 14
Google Scholar
[17] Schimpf D N, Eidam T, Seise E, Hädrich S, Limpert J, Tünnermann A 2009 Opt. Express 17 18774
Google Scholar
[18] Yu C X, Kansky J E, Shaw S E J, Murphy D V, Higgs C 2006 Electron. Lett. 42 1024
Google Scholar
[19] Weiss S B, Weber M E, Goodno G D 2012 Opt. Lett. 37 455
Google Scholar
[20] Goodno G D, Weiss S B 2012 Opt. Express 20 14945
Google Scholar
[21] Rainville A, Whittlesey M, Pasquale C, et al. 2024 Optica 11 1540
Google Scholar
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图 1 四路相干合成系统示意图, 其中Front end为光纤前端, QWP为1/4波片, HWP为半波片, TFP为薄膜偏振片, DM为双色镜, HR为高反镜, L为透镜, PBS为偏振分束棱镜, PZT为压电陶瓷, LD为半导体泵浦源, Rod-type fiber为棒状光纤, BS为分束镜, Filter为滤波片, PD为光电探测器, Control circuit为电控锁相回路, TG为透射光栅对
Fig. 1. Schematic setup of the four-channel coherent beam combining system, where Front end is fiber front end, QWP is quarter-wave plate, HWP is half-wave plate, TFP is thin-film polarizer, DM is dichroic mirror, HR is high-reflection mirror, L is lens, PBS is polarizing beam splitter, PZT is piezo-electric ceramic transducer, LD is laser diode pump, Rod-type fiber is rod photonic crystal fiber, BS is beam splitter, Filter is spectrum filter, PD is photodetector, Control circuit is electronic phase control circuit, TG is transmission gratings.
图 2 输出功率和效率与泵浦功率的关系
Fig. 2. Relationship between output power, efficiency and pump power.
图 3 压缩后脉冲的自相关、光谱与光束质量
Fig. 3. Autocorrelation trace, spectrum and beam quality factor of compressed pulse.
图 5 500 kHz时输出功率和效率与泵浦功率的关系
Fig. 5. Relationship between output power, efficiency and pump power at 500 kHz.
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[1] Chang G Q, Wei Z Y 2020 iScience 23 101101
Google Scholar
[2] Kirsche A, Gebhardt M, Klas R, Eisenbach L, Eschen W, Buldt J, Stark H, Rothhardt J, Limpert J 2023 Opt. Express 31 2744
Google Scholar
[3] Eidam T, Rothhardt J, Stutzki F, Jansen F, Hädrich S, Carstens H, Jauregui C, Limpert J, Tünnermann A 2011 Opt. Express 19 255
Google Scholar
[4] Eidam T, Wirth C, Jauregui C, Stutzki F, Jansen F, Otto H J, Schmidt O, Schreiber T, Limpert J, Tünnermann A 2011 Opt. Express 19 13218
Google Scholar
[5] Kienel M, Müller M, Klenke A, Limpert J, Tünnermann A 2016 Opt. Lett. 41 3343
Google Scholar
[6] Wan P, Yang L M, Liu J 2013 Opt. Express 21 29854
Google Scholar
[7] Stark H, Benner M, Buldt J, Klenke A, Limpert J 2023 Opt. Lett. 48 3007
Google Scholar
[8] Müller M, Aleshire C, Klenke A, Haddad E, Légaré F, Tünnermann A, Limpert J 2020 Opt. Lett. 45 3083
Google Scholar
[9] Jauregui C, Stihler C, Limpert J 2020 Adv. Opt. Photon. 12 429
Google Scholar
[10] Pedersen M E, Johansen M M, Olesen A S, Michieletto M, Gaponenko M, Maack M D 2022 Opt. Lett. 47 5172
Google Scholar
[11] 王栋梁, 史卓, 王井上, 吴洪悦, 张晓辉, 常国庆 2024 物理学报 73 134204
Google Scholar
Wang D L, Shi Z, Wang J S, Wu H Y, Zhang X H, Chang G Q 2024 Acta Phys. Sin. 73 134204
Google Scholar
[12] Peng S X, Wang Z H, Hu F L, Li Z Y, Zhang Q B, Lu P X 2024 Front. Optoelectron. 17 3
Google Scholar
[13] 王志浩, 彭双喜, 徐浩, 李政言, 张庆斌, 陆培祥 2024 光学学报 44 1732017
Google Scholar
Wang Z H, Peng S X, Xu H, Li Z Y, Zhang Q B, Lu P X 2024 Acta Opt. Sin. 44 1732017
Google Scholar
[14] 常洪祥, 靳凯凯, 张雨秋, 张嘉怡, 金坤, 李灿, 粟荣涛, 冷进勇, 周朴 2023 光学学报 43 1714008
Google Scholar
Chang H X, Jin K K, Zhang Y Q, Zhang J Y, Jin K, Li C, Su R T, Leng J Y, Zhou P 2023 Acta Opt. Sin. 43 1714008
Google Scholar
[15] 王涛, 李灿, 刘洋, 任博, 唐振强, 常洪祥, 谢戈辉, 郭琨, 吴坚, 许将明, 冷进勇, 马鹏飞, 粟荣涛, 李文雪, 周朴 2023 红外与激光工程 52 20220869
Google Scholar
Wang T, Li C, Liu Y, Ren B, Tang Z Q, Chang H X, Xie G H, Guo K, Wu J, Xu J M, Leng J Y, Ma P F, Su R T, Li W X, Zhou P 2023 Infrared Laser Eng. 52 20220869
Google Scholar
[16] Ren B, Chang H X, Li C, Wang T, Jin K K, Zhang J Y, Guo K, Su R T, Leng J Y, Zhou P 2024 Front. Optoelectron. 17 14
Google Scholar
[17] Schimpf D N, Eidam T, Seise E, Hädrich S, Limpert J, Tünnermann A 2009 Opt. Express 17 18774
Google Scholar
[18] Yu C X, Kansky J E, Shaw S E J, Murphy D V, Higgs C 2006 Electron. Lett. 42 1024
Google Scholar
[19] Weiss S B, Weber M E, Goodno G D 2012 Opt. Lett. 37 455
Google Scholar
[20] Goodno G D, Weiss S B 2012 Opt. Express 20 14945
Google Scholar
[21] Rainville A, Whittlesey M, Pasquale C, et al. 2024 Optica 11 1540
Google Scholar
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