Yb:CNGG有源反射镜的多程放大特性研究

高效、高平均功率固体纳秒脉冲激光器在光电对抗、激光雷达、材料改性、激光加工等诸多领域发挥着越来越重要的作用，然而目前大多数纳秒级高平均功率激光器采用Yb:YAG或掺Nd材料作为增益介质，材料的高饱和通量或低储能密度会导致激光器放大链路复杂，体积庞大。研究比较了一种更适合作为高平均功率、高脉冲能量激光器增益介质的无序石榴石晶体Yb:CNGG，研究了有源反射镜结构中Yb:CNGG的多程增益特性，分析了放大过程并建立了多程放大模型，在一定的泵浦条件下优化了晶体参数以实现更好的储能。开展了双程放大实验，在15 kW/cm²的泵浦功率密度下得到了1.53倍的增益。对比Yb:CNGG晶体与Yb:YAG晶体的多程放大能力，在相同的晶体参数和泵浦条件下，在入射能量1 mJ时Yb:CNGG可实现2.11 J的脉冲能量输出，优于Yb:YAG晶体1.41 J的能量输出。

Research on multi-pass amplification characteristics of Yb:CNGG active mirror

High efficiency and high average power nanosecond pulsed solid state lasers are playing an increasingly important role in photoelectric countermeasures, lidar, material modification, laser processing and many other fields. However, at present, Yb:YAG or Nd-doped materials are adopted as gain medium in most nanosecond high average power lasers. The high saturation flux or low energy storage density of the materials lead to complex laser amplification link and large laser volume. In this paper, a disordered garnet crystal Yb:CNGG that is more suitable as a gain medium for high average power and high pulse energy lasers is studied and compared. The multi-pass gain characteristics of Yb:CNGG in the structure of active mirror are researched. The amplification process is analyzed and the multi-pass amplification model is established. The crystal parameters are optimized under certain pumping conditions to achieve better energy storage. The double-pass amplification experiment was carried out, and a gain of 1.53 was obtained at the pump power density of 15 kW/cm2. The multi-pass amplification capability of Yb:CNGG and Yb:YAG is compared. Under the same crystal parameters and pumping conditions, the pulse energy output of 2.11 J can be achieved by Yb:CNGG crystal at the incident energy of 1 mJ, which is better than the energy output of 1.41 J of Yb:YAG crystal.