铷蒸气激光器3D理论模型的建立及阈值特性模拟

基于三能级速率方程理论,结合惠更斯-菲涅尔衍射积分公式,利用分步光束传播方法建立了半导体泵浦碱金属蒸气激光器(DPAL)端面泵浦3D理论计算模型,用于模拟研究铷蒸气激光器的泵浦阈值特性。该模型将光束传播、光与物质相互作用独立考虑,利用迭代算法求解。考虑激光器腔内模式与泵浦光模式匹配对阈值特性的影响,模拟了单端泵浦铷蒸气激光器内部的三维动力学过程。在具体算例中研究了模式匹配最佳时,在阈值工作状态下铷蒸气室中的三维粒子数分布,以及沿不同轴线的增益分布。仿真了在最佳模式匹配位置附近,泵浦光模式变化对阈值特性的影响。根据蒸气池中粒子数分布和光场分布具体分析了模式匹配影响阈值特性的机理。同时还模拟了不同长度蒸气池对阈值特性的影响。结果表明,腔参数与泵浦光模式之间存在一定的关系,对于特定的泵浦光模式,存在恰当的腔参数,使得阈值达到最小。

3D model and simulative investigation of threshold characteristics of diode pumped Rb vapor laser

In this paper, we first built a 3D model for diode pumped alkali vapor laser (DPAL) based on the three-level rate equations and split-step beam propagation method, which can be used to simulate the kinetic process of end-pumped single-pass Rb vapor laser. This model considered beam propagation and light interaction with matter respectively. This model was solved by the iteration method. As an example, the distribution for population inversion which is under the optimal mode-matching and gain through different axis was investigated. Then we calculated the influence of mode-matching on the threshold and explained this influence by the distribution of particles and light field distribution. Finally we analyzed the influence of the length of gain cell on threshold characteristics. It turned out that the parameter of the cavity is related to the mode of pumped laser. The threshold will be the minimum value when the cavity parameters and the pumped laser mode are properly selected.