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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Cr~(4+):YAG热管理技术,并优化设计了放大器Cr~(4+):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Cr~(4+):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Cr~(4+):YAG结构,降低与增益介质相邻Cr~(4+):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%、0.8λ;进一步合理地设计Cr~(4+):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。
Aiming at the problem of thermal effect in Yb: YAG laminated laser amplifier with low-temperature helium cooling under high repetition rate operation, a multi-layer Cr4 +: YAG thermal management technology is proposed and the optimized design of amplifier Cr ~ (4 +): YAG spacer layer and edging structure to reduce the effect of thermal effect. The distributions of temperature and stress and strain in different Cr ~ (4 +): YAG laser media were analyzed by using the three-dimensional finite element method and the Jones matrix method. The demagnetization loss and wavefront distortion of the thermally induced birefringence were simulated. Numerical results show that the lateral temperature difference in the gain region can be reduced to 1.5 by designing the two-layer and three-layer Cr4 +: YAG structures to reduce the thermal deposition in the Cr4 +: YAG adjacent to the gain medium K, the average depolarization loss and wavefront distortion can be reduced to 0.5% and 0.8λ respectively after the beam passes through the amplifier. Further rational design of the layer number and absorption coefficient of Cr 4+: YAG can effectively eliminate the effect of heat on the light beam Quality impact.