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在脉冲激光二极管(LD)端面抽运固体激光器中,存在热效应瞬态过程,即晶体的温度分布具有时变性,晶体温度的时变过程受到热弛豫时间的影响.从热传导方程出发,采用解析法和数值法分别对晶体降温过程中温度的时变性进行计算;采用有限元方法,对晶体热弛豫时间及其影响因素进行数值计算,分析了晶体直径、密度、热传导系数和比热等热物性参数对热弛豫时间的影响;采用流体流动换热理论,充分考虑了冷却水流温度和速度对晶体温度分布的影响.结果表明,通过调整晶体尺寸、冷却系统可以实现对热弛豫时间的控制.根据有限元软件ANSYS的计算结果,分析了晶体抽运端面上径向温度的时变分布,晶体边缘与中心的温差和光程差;初步计算了晶体热透镜不同径向位置处的焦距差.结果表明,晶体冷却过程中,不同径向位置与中心的温差和相对光程差具有时变性,晶体热透镜的聚焦特性也是随时间变化的.
In the pulsed laser diode (LD) end-face pumped solid-state laser, there is thermal transient process, that is, the temperature distribution of the crystal is time-varying, and the time-varying process of the crystal temperature is affected by the thermal relaxation time.According to the thermal conduction equation, Method and numerical method were used to calculate the time-varying temperature of the crystal during the cooling process. The thermal relaxation time of the crystal and its influencing factors were numerically calculated by finite element method. The crystal diameter, density, thermal conductivity and specific heat Physical parameters of the thermal relaxation time; the use of fluid flow heat transfer theory, taking full account of the cooling water temperature and velocity on the crystal temperature distribution.The results show that by adjusting the crystal size, the cooling system can achieve the thermal relaxation time Control.According to the calculation results of the finite element software ANSYS, the time-varying distribution of the radial temperature on the end face of the crystal, the temperature difference and the optical path difference between the edge and the center of the crystal are analyzed, and the focal length difference The results show that the temperature difference and relative optical path length difference between different radial positions and centers are time - Focusing properties also varies with time.