基于远场同轴全息的激光M^(2)因子测量技术  

Measurement Technology of Laser M^(2)Factor Based on Far-Field Coaxial Holography

作　　者：李俊博 刘斯靓 韩志刚 李方欣 杨振营 芮九多 王琦 朱日宏[1,2] Li Junbo;Liu Siliang;Han Zhigang;Li Fangxin;Yang Zhenying;Rui Jiuduo;Wang Qi;Zhu Rihong(College of Electronic Engineering and Optoelectronic Technology,Nanjing University of Science and Technology,Nanjing 210094,Jiangsu,China;MIIT Key Laboratory of Advanced Solid Laser,Nanjing University of Science and Technology,Nanjing 210094,Jiangsu,China)

机构地区：[1]南京理工大学电子工程与光电技术学院,江苏南京210094 [2]南京理工大学先进固体激光工信部重点实验室,江苏南京210094

出　　处：《光学学报》2023年第14期49-56,共8页Acta Optica Sinica

基　　金：国家自然科学基金(61875087)。

摘　　要：激光光束质量M^(2)因子的动态测量对激光器的设计、制造与应用均具有重要意义。本文提出了一种基于远场同轴全息的光纤激光器光束质量M^(2)因子动态测量方法。通过偏振移相同轴全息技术直接获取待测激光的远场复振幅信息,利用角谱传输及透镜变换理论求解激光在自由空间中的光场强度分布,从而实现M^(2)因子的动态测量。实验搭建了远场同轴全息装置,测量了不同纤芯直径光纤在632.8 nm波长下的激光光束质量,其结果与BEAM SQUARED商用光束质量仪的测量结果一致。本文所提方法仅需0.02 s即可实现光纤激光的M^(2)因子测量,比商用光束质量仪的测量速度提高了两个数量级以上。此外,本装置结构紧凑,能够避免透镜引入的装调及加工误差。Objective Fiber lasers have been widely used in industry,national defense,and other fields,with the advantages of compact structure,high efficiency,and flexible energy transmission.Beam quality is one of the most important parameters of the fiber laser and directly determines the performance and propagation effects of the laser.Various beam quality parameters have been proposed so far,such as factor M^(2),Strehl ratio,barrel power,and diffraction limit multiples.In all these parameters,factor M^(2) is a relatively perfect evaluation parameter of the laser beam quality and can reflect both the nearfield and farfield characteristics of the laser.With the increase in the laser power,thermal accumulation and nonlinear effects in the laser can cause dynamic changes in the beam quality.Dynamic measurement of factor M^(2) is beneficial to reveal the physical mechanism of mode field changes of the laser and control the realtime distribution of the laser mode field.Therefore,it has great significance to the design,manufacture,and application of lasers.Methods In this study,we propose a dynamic measurement method of factor M^(2) of a fiber laser using coaxial interferometry.The farfield complex amplitude of the laser under test is determined by the spatially phaseshifted coaxial interferograms.The intensity distributions of the laser at different places in the vicinity of the laser nearfield are then obtained through angular spectrum transmission and lens transformation.Factor M^(2) of the laser is finally determined by fitting the beam diameters at different places.Our new method has a compact structure that avoids manufacturing and assembly errors caused by optical lenses.Compared with offaxis holographic technology,the method described in this study can obtain fast,highprecision,and complex amplitude information with high resolution and realize the fast and accurate measurement of laser beam quality factor M^(2) factor.Results and Discussions In order to verify the feasibility of the factor M^(2) measurement method,the

关 键 词：光纤光学与光通信 光束质量M^(2)因子 同轴移相干涉 角谱传输 透镜变换 

分 类 号：O436[机械工程—光学工程]