高功率线偏振窄线宽光纤激光器TMI抑制  

Suppression of TMI in high-power linearly polarized narrow linewidth fiber laser

作　　者：崔国栋 赵鸿[1] 张利明[1] 张大勇[1] 吕华昌[1] CUI Guo-dong;ZHAO Hong;ZHANG Li-ming;ZHANG Da-yong;LV Hua-chang(The 11th Research Institute of CETC,Beijing 100015,China)

机构地区：[1]中国电子科技集团公司第十一研究所,北京100015

出　　处：《激光与红外》2024年第5期692-696,共5页Laser & Infrared

摘　　要：高功率线偏振窄线宽光纤激器在功率光谱合成、相干探测等方面具有广泛的应用前景。在高功率线偏振窄线宽光纤激光器中,模式不稳定(TMI)效应是限制其功率提升的主要因素之一。本文分析了TMI效应对高功率线偏振窄线宽光纤激光器输出功率的影响,提出了TMI效应的抑制方法。文章采用长波泵浦技术,输出功率100 mW的单频激光器作为种子源,相位调制器将种子源线宽展宽至25 GHz,经三级放大,最终实现了线宽25 GHz、功率2.2 kW、中心波长1064 nm、消光比98%的线偏振窄线宽激光输出,光束质量M_(x)^(2)=1.2、M_(y)^(2)=1.21。分析了泵浦波长对TMI效应的影响:由于光线芯径较小(20μm),增益光纤对泵浦光吸收系数较高(1.8 dB/m@976 nm),纤芯温度较高,加上泵浦光量子亏损引入的热,导致纤芯折射率发生变化,较低功率下发生TMI效应,当泵浦波长向长波偏移时,泵浦光的量子亏损降低,同时泵浦吸收系数也降低,无论在光纤全长、还是单位长度上的热分布均减小,增大了TMI阈值,提升了线偏振窄线宽光纤激光器的输出功率。Recently,high-power linearly polarized narrow linewidth fiber lasers are widely applied in coherent detection and wavelength beam combining.Inhigh-power linearly polarized narrow linewidth fiber lasers,the effect of mode instability(TMI)is one of the mainfactors limiting its power increase.In this paper,the influence of TMI effect on the output power of high-power linearlypolarized narrow-linewidth fiber laser is analyzed,and the suppression method of TMI effect is proposed.Long-wavepumping technologies are used in this article.A single frequency laser with an output power of 100 mW is used as theseed source.And the phase modulator broadens the linewidth of the seed source to 23 GHz.After three stageamplification,the linewidth of 23 GHz,power of 2.2 kW,and center wavelength of 1064nm are finally realized.Linearlypolarized narrow linewidth fiber laser output with extinction ratio of 98%is achieved.Beam quality is M_(x)^(2)=1.2 and M_(y)^(2)=1.21.The influence of the pump wavelength on the TMI effect is analyzed.Due to the small core diameter of thefiber(20μm),a high absorption coefficient of the gain fiber for the pump light(1.8 dB/m@976 nm),the core temperatureis high.And the heat introduced by the pump photo quantum defect,causes the refractive index of the fiber core tochange.Finally,the TMI effect occurs at lower power.When the pump wavelength is shifted to the long wavelength,thequantum defect of the pump light and the pump absorption coefficient are both reduced.The heat distribution on theentire length of the fiber or on the unit length is reduced.The TMI threshold is increased.And the output power of thelinearly polarized narrow linewidth fiber laser is improved.

关 键 词：光纤激光器 线偏振 窄线宽 模式不稳定 

分 类 号：O437[机械工程—光学工程] TN248[理学—光学]