离轴抽运厄米-高斯模固体激光器  

Off-axis pumped Hermite-Gaussian mode solid-state laser

作　　者：连天虹[1] 王石语 寇科 刘芸[1] Lian Tian-Hong;Wang Shi-Yu;Kou Ke;Liu Yun(School of Mechanical and Precision Instrument Engineering,Xi’an University of Technology,Xi’an 710048,China;School of Physics and Optoelectronic Engineering,Xidian University,Xi’an 710071,China)

机构地区：[1]西安理工大学机械与精密仪器工程学院,西安710048 [2]西安电子科技大学物理与光电工程学院,西安710071

出　　处：《物理学报》2020年第11期104-115,共12页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:61805196,61805195);陕西省自然科学基础研究计划(批准号:2018JQ6097);陕西省教育厅专项科研计划(批准号:17JK0559)资助的课题.

摘　　要：给出了离轴抽运固体激光器多模速率方程组在阈值附近的小信号求解方法,用这种方法研究了模式随离轴量的变化以及厄米-高斯模的竞争行为.抽运光斑较小时,离轴量增加高阶模式依次出现;抽运光斑较大时,模式变化呈现复杂性.用小信号近似得到的模式光子数比例与较高抽运功率下数值求解速率方程组的结果接近,表明可以用该方法估算实际较高功率激光器的模式分布,这可以方便这类激光器的研究.对离轴抽运下的多厄米-高斯模激光器,阈值附近的模竞争体现为,随着抽运功率的增加,第一个净增益由负变正的模式,光子数随即开始增加,增加趋势接近线性.而第二个净增益由负变正的模式,光子数并不立即开始增加,而要等到抽运功率进一步增加后才开始增加,其开始增加后第一个模式的增长趋势变缓.从动态过程看,各个模式经过交叉尖峰和交叉弛豫振荡竞争后,逐渐达到稳态.实验获得了HG00-HG50模光束,实验所得到的模式分布与理论计算结果符合很好.To study the modes’pattern and the modes’competition behavior of an off-axis pumped solid-state laser,a small signal approximation method is derived,which simplifies the multiple-mode differential equations into liner algebraic equations.When the pump beam radius is small,the higher-order Hermite-Gaussian modes emerge successively with the off-axis displacement increasing,while the pattern evolution shows some complexity when the pump radius is larger.The percentage of the modes with a small pump power near the threshold,calculated with the small signal method,is close to that calculated at a higher pump power by directly solving the rate equations numerically.This indicates that we can estimate the modes’pattern of an actual high power laser by using the small signal method.For a multiple Hermite-Gaussian modes off-axis pumped solid state laser,as the pump power increases,the photon number of the mode increases linearly as its net gain becomes positive,while that of the second mode with a smaller net gain does not increase immediately as it becomes positive successively.Larger pump power is required until the photon number begins to increase.The increasing slope of first mode decreases as the second mode begins to grow.The dynamics of the modes’competition presents cross spiking and cross relaxation process before they become stable.Moreover,the outputs of the modes HG00-HG50 are experimentally demonstrated,and the spot evolution with the off-axis displacement agrees very well with the calculated result.

关 键 词：固体激光器 离轴抽运 模式竞争 小信号解 

分 类 号：TN248.1[电子电信—物理电子学]