单脉冲能量3 mJ、重复频率1 kHz皮秒超高斯光束的实现

采用圆孔光阑和空间滤波-像传递系统相结合，实现了高效率的皮秒高斯光束到超高斯光束的整形。通过研究其中空间滤波-像传递系统中滤波针孔大小对整形效果的影响，获得了整形效率大于32%、200~500 mm传播距离内保持超高斯光束填充因子大于0.76传输的实验结果。随后对获得的超高斯光束进行放大，放大过程中通过利用侧面泵浦Nd:YAG晶体的热透镜代替放大光路中4F系统像传递系统中的透镜，简化了超高斯皮秒激光放大系统的结构，同时经过一级双通放大后，获得了近场填充因子0.72，单脉冲能量3.0 mJ，脉冲宽度11 ps，重复频率1 kHz，峰值功率密度8 GW/cm2的超高斯光束皮秒激光放大输出。

Realization of single-pulse energy 3 mJ,repetition frequency 1 kHz picosecond super-Gaussian beam

A picosecond beam with Gaussian profile was efficiently shaped into a super-Gaussian profile beam by a circular aperture combined with a spatial filter-image relaying system. By studying the influence of the size of the filter aperture on the shaping effect in the spatial filter-image relaying system, the experimental results for maintaining the filling factor of the super-Gaussian beam greater than 0.76 in the propagation distance of 200 mm to 500 mm was obtained, and the corresponding efficiency of this beam shaping method was over 32%. Then, the beam with a super-Gaussian distribution was amplified. By using the thermal lens of semiconductor laser side pumped Nd:YAG crystal to replace the lens in the 4F image relaying system, the structure of the super-Gaussian picosecond laser amplification system can be simplified. After double-passing the single Nd:YAG crystal, a picosecond super-Gaussian profile beam with a near-field fill factor of 0.72, 1 kHz repetition rate, 11 ps duration and 3.0 mJ single-pulse energy was obtained, and the corresponding peak power intensity was up to 8 GW/cm2.