超快光纤激光中的非线性脉冲放大技术(特邀)  

Nonlinear Amplification Techniques for Ultrafast Fiber Lasers(Invited)

作　　者：陈润植 邢宇婷 张瑶 王栋梁 王军利 魏志义[1,3,4] 常国庆 CHEN Runzhi;XING Yuting;ZHANG Yao;WANG Dongliang;WANG Junli;WEI Zhiyi;CHANG Guoqing(Key Laboratory of Optical Physics,Institute of Physics,Chinese Academy of Sciences,Beijing 100190,China;School of Physics and Optoelectronic Engineering,Xidian University,Xi'an 710071,China;University of Chinese Academy of Sciences,Beijing 100049,China;Songshan Lake Materials Laboratory,Dongguan,Guangdong 523808,China)

机构地区：[1]中国科学院物理研究所光物理重点实验室,北京100190 [2]西安电子科技大学物理与光电工程学院,西安710071 [3]中国科学院大学,北京100049 [4]松山湖材料实验室,广东东莞523808

出　　处：《光子学报》2022年第7期309-326,共18页Acta Photonica Sinica

基　　金：国家自然科学基金(No.62175255);国家重点研发计划(No.2021YFB3602602)。

摘　　要：高功率高能量飞秒光纤激光系统通常采用主振荡器加功率放大器结构。在放大飞秒脉冲时,非线性效应是制约脉冲能量的主要因素。基于传统啁啾脉冲放大技术的光纤激光系统虽然能够产生能量在1 mJ量级的飞秒脉冲,但是所产生的脉冲通常在200 fs以上,无法直接满足能量要求较低(1~100μJ范围之内)、脉冲宽度却更短(60 fs以下甚至更短)的应用需求。与啁啾脉冲放大技术通过展宽脉冲而减少非线性相移相反,非线性放大故意保持脉冲的宽度在皮秒量级从而积累大量的非线性相移,导致放大后脉冲的光谱展宽为输入光谱的数倍,经过传统光栅对压缩后能够产生60 fs以下的近变换极限脉冲。本文主要以掺镱光纤放大系统为例,重点介绍自相似抛物线脉冲放大、预啁啾管理放大、增益管理放大和非线性分脉冲放大四种非线性光纤放大技术的工作原理、发展现状以及未来趋势。将提出的预啁啾管理分脉冲放大与多路相干合成相结合,有望产生重复频率1 MHz、平均功率超过1 kW、脉冲能量1 mJ左右的亚50 fs脉冲。这种千瓦级高重复频率、高能量飞秒脉冲源在基础科学、激光加工等领域中具有潜在的应用。High-power and high-energy femtosecond fiber laser usually consists of a master oscillator followed by a power amplifier. Nonlinear effects are the main factor restricting the amplified pulse energy.Although traditional chirped pulse amplification can generate femtosecond pulses with an average power of ~1 kW and a 1 mJ level pulse energy in a single large-mode-area Yb-doped fiber,the obtained pulse duration is limited to >200 fs. However,various applications require modest pulse energy(1~100 μJ)but a much shorter pulse duration(<60 fs). Such applications include high-order harmonic generation based on cavity enhancement technology to generate extreme ultra-violet pulses,multi-beam driven high-speed nonlinear optical imaging,and wide-spectrum mid-infrared optical frequency comb based on intra-pulse difference frequency generation,etc. This review paper focus on nonlinear pulse amplification techniques in ultrafast fiber laser systems. In contrast to chirped pulse amplification that reduces the nonlinear phase shift by broadening the pulse,the nonlinear amplification techniques maintain the amplified pulse duration in picosecond level to accumulate large nonlinear phase shift,resulting in a substantial spectral broadening.The amplified spectrum is several times wider than the input spectrum. The amplified pulse develops a nearly linear chirp that can be compressed to <60 fs in duration by a traditional grating pair. We describe the working principles and state of the art of four nonlinear fiber amplification technologies developed for Yb-doped fiber amplifiers: 1) self-similar parabolic pulse amplification, 2) pre-chirp managed amplification,3)gain managed amplification,and 4)nonlinear divided-pulse amplification.In the self-similar amplification technique,the amplified pulse asymptotically evolves into a linearly chirped parabolic similariton due to the interplay of positive dispersion,self-phase modulation and gain.Such amplified pulse with linear chirp can be readily compressed by Treacy-type grating pair. The

关 键 词：超快光纤激光 自相似抛物线脉冲放大 预啁啾管理放大 增益管理放大 预啁啾分脉冲放大 

分 类 号：TN248[电子电信—物理电子学] TN253