激光二极管直接后向泵浦的高光束质量万瓦光纤激光器  

Laser diode directly backward pumped high-beam-quality 10-kW fiber laser

作　　者：文榆钧 王鹏[1,2,3] 奚小明 张汉伟 黄良金[1,2,3] 杨欢 闫志平 杨保来 史尘 潘志勇 王小林 王泽锋 许晓军[1,2,3] Wen Yu-Jun;Wang Peng;Xi Xiao-Ming;Zhang Han-Wei;Huang Liang-Jin;Yang Huan;Yan Zhi-Ping;Yang Bao-Lai;Shi Chen;Pan Zhi-Yong;Wang Xiao-Lin;Wang Ze-Feng;Xu Xiao-Jun(College of Advanced Interdisciplinary Studies,National University of Defense Technology,Changsha 410073,China;Nanhu Laser Laboratory,National University of Defense Technology,Changsha 410073,China;State Key Laboratory of Pulsed Power Laser Technology,Changsha 410073,China)

机构地区：[1]国防科技大学前沿交叉学科学院,长沙410073 [2]国防科技大学,南湖之光实验室,长沙410073 [3]脉冲功率激光技术国家重点实验室,长沙410073

出　　处：《物理学报》2022年第24期176-183,共8页Acta Physica Sinica

基　　金：国家自然科学基金青年科学基金(批准号:62005315);长沙市杰出创新青年培养计划(批准号:kq2106008)资助的课题。

摘　　要：高功率高光束质量光纤激光器在工业生产中得到了广泛应用,但其受到光纤中非线性效应等现象的制约,进一步功率提升严重受阻.本文基于大模场低数值孔径增益光纤搭建了激光二极管直接泵浦的全光纤激光放大器.通过改变增益光纤的弯曲直径,有效地提升了动态模式不稳定阈值,实现了最高功率10.53 kW,光光转换效率74.04%,光束质量因子M^(2)~2.88的激光输出.研究表明,在少模光纤激光放大器中,提升输出功率与改善光束质量的方法相互制约.不考虑光束质量时激光器可以较为简单的获得万瓦乃至更高功率输出;但是在提升功率的同时保持光束质量不退化是一件充满挑战且难度极大的工作.Fiber lasers have been widely used in the industrial and scientific fields due to their advantages of high conversion efficiency,simple thermal management,and consistent stability.High brightness and high-power fiber lasers are affected by stimulated Raman scattering and transverse mode instability,which limits the power scaling of fiber lasers.Therefore,there are only a few researches achieving a 10 kW-level fiber laser system by laser diode direct pumping or tandem pumping.In this work,we demonstrate an all-fiber laser amplifier based on home-made low numerical aperture(NA)fiber pumped by 976 nm laser diodes.When the signal light is input to the gain fiber with a minimum bending diameter of 12 cm,the beam quality factor M^(2)is about 1.72.The onset of transverse mode instability(TMI)is observed at 2467 W output power,accompanied by beam quality degradation.In order to suppress the onset of TMI,the minimum bending diameter of the gain fiber is changed from 12 cm to 20 cm.And the signal light is input into the gain fiber with a bending diameter of 28cm.Benefiting from this operation,the fiber laser amplifier achieves maximum output power of 10.53 kW with an optical-to-optical efficiency of 74.04%,and there is no TMI onset observed.However,increasing bending diameter inevitably leads the beam quality to degrade.At the maximum output power,the beam quality factor M^(2)is 2.88.To the best of our knowledge,this is the highest optical-to-optical efficiency and the best beam quality in 10 kW-level laser diodes pumping fiber lasers.Generally,it is believed that reducing bending diameter can suppress TMI by increasing high-order mode loss.However,this rule is not applicable to few-mode fiber lasers.A larger bending diameter leads more high-order modes to be contained in the signal light instead of leaking into the cladding area.Thus,a higher output and poor beam quality are obtained.Also,it is believed that tightly coiled fiber can make mode coupling easier and trigger off TMI,which results in a positive correlation betw

关 键 词：掺镱光纤激光器 模式不稳定效应 弯曲直径 

分 类 号：TN248[电子电信—物理电子学]