针对高重复频率运行下低温氦气冷却的间隔掺杂Yb:YAG叠片激光放大器中热效应的问题, 提出了一种多层Cr4+:YAG热管理技术, 并优化设计了放大器Cr4+:YAG间隔层和包边结构以减少热效应的影响。利用三维有限元和琼斯矩阵方法, 分析了不同Cr4+:YAG结构激光介质中温度和应力应变分布, 并模拟计算了热致双折射退偏损耗和波前畸变。数值结果表明, 通过设计两层和三层Cr4+:YAG结构, 降低与增益介质相邻Cr4+:YAG中的热沉积, 增益区内的横向温差可降低到1.5 K以内, 光束经过整个放大器后平均退偏损耗和波前畸变可分别减少到0.5%、0.8 ?姿; 进一步合理地设计Cr4+:YAG的层数和吸收系数能有效消除热效应对光束质量的影响。

The thermal management technique of multi-layer Cr4+:YAG medium was presented for mitigating the deleterious impact of thermal effects in a cryogenic helium gas cooled Yb:YAG multislab amplifier with Cr4+:YAG interlayers operating at a high repetition rate, by means of optimizing the architectures of Cr4+:YAG interlayers and claddings in the laser slabs. The distributions of temperature, stress, depolarization losses and optical path difference in four amplifier architectures with different Cr4+:YAG parameters were numerically calculated by a three-dimensional finite element analysis and the Jones matrices method. Based on these results of the propsed modelling, it was showed that the properly designed two-layer and three-layer Cr4+:YAG could decrease the heat deposition of the Cr4+:YAG around the gain media, and hence result in a very small transverse temperature gradient (<1.5 K) in the first slab. When the laser beam traveled through the whole amplifier, the average thermal-stress induced depolarization losses and optical path difference for the laser amplifier head were reduced to 0.5% and 0.8 ?姿, respectively. Furthermore, the negative impact of thermal effects on the output beam quality can be vanished by properly designing the number, widths, and absorption coefficients of the multi-layer Cr4+:YAG medium, which are beneficial for the engineering/design of the next generation of high energy, high power lasers.