基于非线性调控的高功率时空锁模光纤激光器  

High-Power Spatiotemporal Mode-Locked Fiber Laser Based on Nonlinear Regulation

作　　者：袁家琪 李阳[1] 方振 张祖兴[1] Yuan Jiaqi;Li Yang;Fang Zhen;Zhang Zuxing(College of Electronic and Optical Engineering&College of Flexible Electronics(Future Technology),Nanjing University of Posts and Telecommunications,Nanjing 210023,Jiangsu,China)

机构地区：[1]南京邮电大学电子与光学工程学院、柔性电子(未来技术)学院,江苏南京210023

出　　处：《中国激光》2024年第13期51-57,共7页Chinese Journal of Lasers

基　　金：国家自然科学基金(62175116);南京邮电大学1311人才计划。

摘　　要：提出并研究了一种基于非线性调控的高功率时空锁模光纤激光器。在时空锁模光纤激光器中,克尔非线性导致的光束自净化效应使得分散的高阶模能量集中到基模上,有利于改善光束质量。但过高的基模功率引入了较大的非线性效应,在高泵浦功率条件下导致脉冲分裂,限制了所能得到的最大单脉冲能量。通过调控多模光纤间的熔接错位量来激发更多的高阶模,利用大错位量激发的多横模平衡光束自净化效应带来的过高非线性,从而在高泵浦功率条件下得到稳定的单脉冲输出。实验中,当错位量为8μm时,输出的最大空间光平均功率达690 mW,相应的单脉冲能量达39 nJ。时空锁模光纤激光器中的非线性调控有助于进一步理解多模光纤中的非线性,并为高功率锁模激光器提供了一个新的制备方案。Objective Fiber lasers have been widely used in fields such as optical communication, radar, and signal processing, and have an irreplaceable role. Single-mode fiber(SMF) lasers typically operate at a low power and generate pulses by locking multiple longitudinal modes that are the fundamental transverse modes. However, the small mode-field area of single-mode fibers can easily lead to strong nonlinear effects, thereby limiting the performance of single-mode lasers. Owing to the limitations of the soliton area theorem and spectral sideband effect, the maximum energy of a single soliton pulse can only reach the order of 0.1 nJ. This is because nonlinearity and anomalous dispersion often lead to pulse splitting. In a dissipative soliton laser with a positive dispersion cavity, large nonlinearity can induce multiple pulses. Compared with SMFs, graded-index multimode fibers(GIMFs) can support hundreds of lateral modes, have a higher transmission capacity, carry more energy, and have complex spot characteristics. In this study, we propose a nonlinear regulation technique and implement a high-power spatiotemporal mode-locked(STML) fiber laser using nonlinear polarization rotation(NPR). The number of modes and nonlinearity in the cavity are controlled by changing the fusion misalignment between the gain and multimode fibers. By adjusting the misalignment amount to 8 μm, the maximum average spatial light power output by the laser can reach 690 mW, and the single pulse energy can reach 39 nJ at a repetition rate of 17.67 MHz. This is a suitable solution for generating high-power laser pulses.Methods In the current laser configuration, we first set the fusion misalignment amount between the gain fiber and GIMF to 0. In other words, there is no misalignment fusion, enabling the fiber cavity to achieve STML operation in the few-mode state. In this case, the pump light can increase from 1.32 W to 1.92 W for maintaining a single-pulse output with a maximum spatial output power of 264 mW and intracavity single-pulse energy of

关 键 词：时空锁模激光器 多模光纤 克尔非线性 光束自净化 

分 类 号：TN248[电子电信—物理电子学]