外腔谐振倍频是获得397.5 nm 紫外激光的重要方法。搭建了基于周期极化的磷酸氧钛钾(PPKTP)晶体的半整体谐振腔，对经半导体锥型放大器放大的795 nm 单频连续激光进行谐振倍频。在203 mW 的795 nm 基频光输入条件下，实现了60.4 mW 的397.5 nm 连续单频紫外激光输出，倍频转化效率为30%；在基频光功率约87.5 mW 时，得到最大的倍频效率约为34.6%。倍频紫外光光束质量因子M2优于1.21，光束质量良好，30 min内典型的倍频光功率均方根起伏小于1.9%。该倍频器结构紧凑，具有很好的机械稳定性，可实现紫外激光的稳定输出，可用于产生对应铷原子跃迁线的压缩、纠缠态光场，在量子光学和精密测量等领域发挥重要作用。

Frequency doubling in an external cavity is a prevalent method to generate an ultra- violet laser at 397.5 nm . A semi-monolithic resonant frequency doubling cavity based on the PPKTP crystal is built and is used to realize the resonant frequency doubling of the 795 nm single frequency continuous-wave laser amplified via a semiconductor tapered amplifier. Under the condition of 203 mW input power of a 795 nm laser, the 397.5 nm single frequency continuous-wave ultra-violet laser with a power of 60.4 mW is obtained, and the frequency doubling conversion efficiency is 30%; and the maximum doubling efficiency is 34.6% with a fundamental power of about 87.5 mW. The beam quality factor M2 of the frequency doubling ultra-violet laser is superior to 1.21, indicating the better beam quality. The typical root-mean-square fluctuation of the output power within 30 min is less than 1.9%. This frequency doubler is compact, has good mechanical stability, and can be used to achieve steady output of ultraviolet laser. The ultra- violet laser can be used to generate the squeezed or entangled states of the rubidium transitionline, and plays an important role in the quantum optics, precise measurement and other fields.