为研制高功率的板条功率放大模块, 对Nd:YAG板条激光器的增益介质的热结构进行了研究。采用有限元方法仿真了高功率激光二极管阵列端面抽运Nd:YAG板条介质的温度、应力分布, 数值模型考虑了抽运光在介质内的不均匀分布。结果表明,板条介质掺杂和未掺杂结合部位温度和应力最高, 是整个板条介质的薄弱环节, 应优化设计避免板条破裂。以此为参考设计高功率放大模块, 而后搭建激光放大链路, 种子光功率2.5 W, 通过一级预放模块四程放大后, 再经过四级功放模块双程放大, 实现了11 kW激光输出。实验中测量了高功率抽运条件下增益介质的温度分布,与数值仿真结果基本符合。

Thermal effect of Nd:YAG slab gain medium is studied for solid slab high power amplifier. The investigation uses the finite element method to simulate the distribution of temperature and stress of Nd:YAG slab gain medium with edge pump by high power laser diode array, considering uneven pump distribution in gain medium. The result shows that the temperature and stress of the bonding part of doped and undoped YAG are the highest. It is the weakness of the slab gain medium and should be designed optimum for avoiding slab Nd:YAG damage . Refer to the result, the power amplifier is designed. The laser chain is built, and the seed laser of 2.5 W power is amplified by a four-pass pre-amplifier and four stage double-pass power amplifier. The laser chain achieves 11 kW laser average power. The temperature distribution of slab gain medium with high power pump is measured in the experiment. The experimental result agrees well with the simulation.