30 W输出的Yb3+:KGd(WO4)2激光系统的理论设计

Yb3+:KGd（WO4）2晶体具有增益带宽大、掺杂浓度高等突出特点，是近年来引起广泛关注的可用于构建锁模飞秒和辐射平衡激光系统的激光介质。这里建立了基于准三能级系统的微观动力学理论模型，并将其应用于端面泵浦Yb3+:KGd（WO4）2种子源和激光放大系统的理论分析中。首先从速率方程出发，讨论了准三能级激光系统的种子源部分的物理特性，指出种子源部分存在着最佳的晶体长度和输出耦合镜反射率。由于Yb3+:KGd（WO4）2晶体材料的热传导率很低，研究中拟采用主控振荡功率放大结构以实现30 W量级的激光输出，并在此基础上探讨了主控振荡功率放大器部分的输出物理特性。研究结果对将来构建实用化的Yb3+:KGd（WO4）2激光系统有着重要的理论指导意义。

Theoretical design of a Yb3+: KGd(WO4)2 laser system with 30 W output power

Yb3+:KGd (WO4)2 crystal has been paid much attention in the recent years because of its broad gain bandwidth and high dopant concentration and it is considered as an ideal laser medium for constructing a mode-locked femtosecond or a radiatio-balanced laser system. A quas-thre-level kinetic model has been built to carry out the theoretical analyses for both the seed part and the amplification part in a Yb3+:KGd(WO4)2 laser system with en-pumped configurations. The research first investigated the physical characteristics of the seed part based on analyses of the rate equations and found that the optimal crystal length and optimal output coupler reflectivity should exist in a lasing oscillator. Because the thermal conductivity of a Yb3+:KGd (WO4)2 crystal was relatively low, the research employed a master oscillator powe-amplifier (MOPA) to realize the 30 W-output power. Finally, the output physical features of the MOPA part was analyzed. The research results are thought to be useful for construction of a practical Yb3+:KGd(WO4)2 laser system.