多光子纠缠态是量子通讯网络中的重要资源，光与二阶非线性介质相互作用的自发参变下转换过程是目前制备多光子态较成熟的方案之一。尽管脉冲光可以提高非线性转换效率并简化通信协议，但是进一步增强光与介质间的相互作用对提高多光子的产生效率依然必要。设计了飞秒脉冲激光谐振腔系统，在不改变脉冲重复频率和频率梳结构的情况下，提高了下转换过程的参变增益，从而获得更有效的多光子态输出。与传统的脉冲光单次穿过晶体方案相比，单光子与双光子的产生率分别提高6.25倍和38.6倍。实验结果与理论分析基本一致。

Multi-photon entangled states which are produced mainly by the process of spontaneous parametric down conversion between laser and second-order nonlinear material is a key resource in the quantum network. Although the application of pulsed laser improves the nonlinear conversion efficiency and simplifies the quantum communication protocol, it is still necessary to enhance the interaction between laser and material for improvement of multi-photon production rate. A resonant cavity for femtosecond pulse is designed to increase the parametric gain and multi-photon production rate while keeping its repetition rate and comb structure. The improved single- and two-photon production rate of cavity system are enhanced by 6.25 and 38.6 respectively compared with that of the single-pass system. The experimental results show agreement with theoretical predication.