光纤激光基模光束的β因子  

β factor of fundamental mode of fiber laser beam

作　　者：张雨秋 黄良金 常琦 安毅 马鹏飞 冷进勇 周朴[1] Zhang Yu-Qiu;Huang Liang-Jin;Chang Qi;An Yi;Ma Peng-Fei;Leng Jin-Yong;Zhou Pu(College of Advanced Interdisciplinary Studies,National University of Defense 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

出　　处：《物理学报》2021年第20期73-79,共7页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:61805280);湖南省自然科学基金(批准号:2019JJ10005)资助的课题。

摘　　要：光纤激光器凭借其优良特性已在众多领域中得到广泛应用,光束质量是衡量其性能的重要指标之一.M^(2)因子是应用较为广泛的一种评价因子,但已被证明并不适用于非高斯分布的光斑,此时常用b因子来评价.本文以光纤激光基模光束为研究对象,理想光束选取包含LP_(01)模99%能量的圆形实心均匀光束,理论研究了b因子与阶跃折射率光纤中LP_(01)模的各项参数之间的关系.研究发现:采用经典的b因子定义方法,当归一化频率V大于1.8时,LP_(01)模的b值小于1,远场聚焦能力优于理想光束.此外,b因子随归一化频率V、纤芯半径a或数值孔径NA的增大而减小,并且与M^(2)因子呈非线性关系.Owing to the advantages of high conversion efficiency,compactness and reliability,the fiber lasers are widely applied to many scientific areas,such as optical fiber communication,sensing and industrial processing.Beam quality is an important criterion for evaluating the performances of high-energy laser beam systems.Therefore,researchers have been constantly searching for the methods of evaluating the beam quality while pursuing higher output power.Until now,the researchers have proposed many definitions of beam quality.In practice,the evaluation parameters of beam quality include focused spot size,Strehl ratio,far-field divergence angle,diffraction limited b factor,energy circle rate,beam parameter product,and M^(2) factor.Among them,the M^(2) factor is the most suitable for the assessment of beam quality in both the near-field and far-field,which avoids the inaccuracy of the measurement of the beam quality only by the far-field radius or the far-field divergence angle.Thus,the M^(2) factor is recognized as an important standard for evaluating beam quality by the International Organization for Standardization(ISO).However,it proves that the M^(2) factor is not suitable for non-Gaussian distribution spot.On the other hand,in applications of high-energy laser beam transmission and laser industrial manufacturing,people pay more attention to the focusability of laser energy.In this case,the diffraction limited b factor is more suitable for evaluating beam quality.In this paper,we investigate the beam quality of LP_(01) mode of fiber laser by b factor,and a circular and solid homogenous beam with the energy of 99%of LP_(01) mode is considered as an ideal beam.The relationship between b factor and the parameters of LP_(01) mode in a step-index fiber is studied theoretically.It is found that the value of the beam quality b factor is lower than 1 when the normalized frequency V is bigger than 1.8,and the far-field energy focusability of LP_(01) mode is better than the case of ideal beam.Besides,the value of b factor dec

关 键 词：光纤激光 激光光束质量 衍射极限倍数β M^(2)因子 

分 类 号：TN248[电子电信—物理电子学]