21 MHz~100 kHz重复频率亚皮秒NALM锁模光纤激光器  

Sub-Picosecond NALM Mode-Locked Fiber Laser with 21 MHz-100 kHz Repetition Rate

作　　者：石宇航 程昭晨 彭志刚[1,2] 游雨 夏童 王璞[1,2] Shi Yuhang;Cheng Zhaochen;Peng Zhigang;You Yu;Xia Tong;Wang Pu(Institute of Laser Engineering,Faculty of Materials and Manufacturing,Beijing University of Technology,Beijing 100124,China;Beijing Engineering Research Center of Laser Applied Technology,Beijing University of Technology,Beijing 100124,China)

机构地区：[1]北京工业大学材料制造学部激光工程研究院,北京100124 [2]北京工业大学北京激光应用技术研究中心,北京100124

出　　处：《中国激光》2021年第5期183-191,共9页Chinese Journal of Lasers

基　　金：国家重点研发计划(2017YFB0405201);国家自然科学基金(61527822)。

摘　　要：超短脉冲光纤激光器在工业、医学、科研等许多领域有着重要的应用。报道了基于全保偏非线性放大环形镜(NALM,nonlinear amplifying loop mirror)锁模的掺镱光纤激光器,通过调整腔内无源光纤的长度和位置,实现了21 MHz~100 kHz重复频率下的锁模。在21.16 MHz重复频率下实现了3 dB光谱带宽为9.1 nm、脉宽为5.3 ps的单脉冲锁模输出,经压缩后脉宽为352 fs。当重复频率为5.92 MHz时,获得了3 dB光谱带宽最宽为30 nm和压缩脉宽最窄为177 fs的锁模脉冲输出。受限于光纤长度,当最低重复频率为100 kHz时,从振荡器直接输出的锁模脉冲的单脉冲能量为104 nJ,脉宽为300 ps,经压缩后脉宽为1.053 ps。在所有重复频率下,锁模脉冲都具有宽光谱、可压缩至亚皮秒量级等特性,并且不是耗散孤子共振或者类噪声脉冲。其中,当重复频率为388 kHz时,脉宽为62.7 ps、单脉冲能量为20.8 nJ的NALM锁模种子源经过单级光纤放大器后,单脉冲能量可以直接放大到3μJ,最终脉宽可以被压缩至537 fs,整个激光器系统不含脉冲选择器件和额外的多级光纤放大级,结构十分紧凑。Objective The repetition rate of a mode-locked fiber laser pulse is one of the most important defining parameters.On-demand repetition rates vary,serving a wide range of applications.For example,lasers with high pulse repetition rates(between tens of MHz and a few GHz)are not only used to generate optical frequency combs or coherent stacked pulses,but also offer high-precision wavelength calibration for astronomical spectrographs.In contrast,lasers with low pulse repetition rates(below 1 MHz)are highly valued in industrial laser materials processing to keep the characteristics of cooling machining.The mode-locked lasers with high repetition rates can easily be generated by shortening the laser cavity length.However,when it comes to the lasers with low repetition rates,the things get more complex and costly because these lasers require an additional acousto-optic modulator(AOM)or electro-optic modulator(EOM)to pick pulses from a laser source with high repetition rates.Compared with the traditional SESAM(semiconductor saturable absorption mirror)mode-locked fiber lasers,the mode-locked fiber lasers with nonlinear amplifying loop mirrors(NALM)as artificial saturable absorbers demonstrate the advantages of fast relaxing time,high damage threshold,life expectancy,all-fiber structure,and ultralow repetition rates over a relative broadband.These pulses can be generated by elongating the cavity length.After compression,these pulses have a sub-picosecond duration.In this study,we report a sub-picosecond NALM mode-locked fiber laser at different repetition rates varying from 21 MHz to 100 kHz by adjusting the length of the passive fiber at the proper position in the oscillator.All pulses with different repetition rates can be compressed to a sub-picosecond level.Methods We constructed the NALM mode-locked fiber laser based on an all-fiber structure and an all-polarizationmaintaining design.To realize different repetition rates in the mode-locked laser pulse output,we gradually elongated the oscillator cavity length via ins

关 键 词：激光器 锁模激光器 超快激光 非线性放大环形镜 低重复频率 

分 类 号：TN248[电子电信—物理电子学]