受激拉曼散射对高功率激光传输特性影响研究  

Influence of Stimulated Raman Scattering on Propagation Properties of High-Power Laser

作　　者：郑也 倪庆乐 张琳[1] 刘小溪 王军龙[1] 王学锋[1] Zheng Ye;Ni Qingle;Zhang Lin;Liu Xiaoxi;Wang Junlong;Wang Xuefeng(Beijing Institute of Aerospace Control Devices,Beijing 100094,China)

机构地区：[1]北京航天控制仪器研究所,北京100094

出　　处：《中国激光》2021年第7期26-33,共8页Chinese Journal of Lasers

基　　金：国家自然科学基金企业创新发展联合基金(U20B2058)。

摘　　要：研究了高功率光谱组束系统内光路的气体热效应对激光远场光束质量的影响。通过同等功率密度传输的子光束与合成光束的远场光斑分布对比研究,明确了子光束中的受激拉曼散射是造成组束光路气体热效应的主要因素。当拉曼光功率密度仅为180 W/cm^(2)时,远场光斑即出现了中心强度明显下降、能量分散等劣化状态。研究了激光传输路径长度对气体热效应的影响,当光程从100 mm增加至450 mm时,远场光斑的峰值强度逐渐下降,光斑逐渐变散。通过向密封的组束装置中充入氮气,基本可以消除气体热效应对远场光束质量的影响,可作为一种有效的气体热效应抑制手段。研究成果为光谱组束激光器的光束质量优化提供了有效支撑。Objective Spectral beam combining(SBC)is an effective method to achieve a high-power,high beam quality fiber laser.In the SBC system,multi-channel incident lasers are arranged spatially and are combined into a single laser beam via an optical element.The transmitted laser power density in the SBC system is very high due to the high power and small beam diameter.In this case,the thermal blooming effect becomes a nonnegligible factor that influences the far-field beam quality.In addition,a narrow linewidth is required in SBC to eliminate the dispersion effect.As a result,nonlinear effects are easy to stimulate,e.g.,stimulated Brillouin scattering(SBS)and stimulated Raman scattering(SRS),which generates a new wavelength laser.The new wavelength laser may cause enhanced atmospheric absorption and degrade the far-field beam quality.Atmospheric thermal blooming of high-power laser propagation has been studied extensively in the outer path(optical path in atmosphere)and inner path(optical path in the launching system).However,relevant studies of the inside optical path of a high-power laser have not been sufficiently thorough.Therefore,in this paper,the influence of thermal blooming on far-field beam quality in a high-power spectral beam combining system is studied.SRS in the incident narrow linewidth fiber amplifier is verified to be the dominant factor that induces thermal blooming in the beam combining system.In addition,N2 injection into the combining system essentially eliminates the influence of thermal blooming on far-field beam quality,which can be considered an efficient suppression method.Methods A three-channel spectral beam combining system is constructed with central wavelengths of 1064,1072,and 1084 nm,respectively.Each incident laser can deliver 2 kW power.Taking the SRS effect into consideration,we employ 1400 W and 1800 W laser power in this experiment.First,the far-field beam patterns of each incident laser at 1400 W and 1800 W are tested.Then,the far-field beam patterns of the three-channel combined b

关 键 词：激光器 高功率光纤激光 光谱组束 受激拉曼散射 大气热效应 光束质量 

分 类 号：TN012[电子电信—物理电子学]