激光二极管(LD)三向侧面抽运晶体时, 每根抽运源上激光二极管阵列间的散热空隙使得抽运光在晶体中轴向分布不均匀, 晶体的轴向热均匀性变差。从光强分布的解析表达式出发, 通过研究热源分布特性, 导出了工作物质热透镜焦距的理论计算方法。数值计算了总抽运功率不变的情况下, 抽运源激光二极管阵列的空间占空比、抽运源到晶体中心距离等因素对晶体热透镜焦距的影响。发现热透镜焦距随激光二极管阵列空间占空比和抽运距离的增大而增大。结果表明, 抽运光沿轴向分布越均匀, 热透镜焦距越长。这为追求晶体轴向热均匀性时侧面抽运源的选择和改进提供了依据。

In a three-stack side-pumped laser, the gaps between two arrays for cooling make the pump light nonuniform and affect the thermal uniformity in the crystal. Based on the light intensity equation and the distribution characteristic of hot source, numerical method for thermal lens focus is proposed. With the total pumping power unchanged, the effects of dimensional duty factor of arrays and the distance between LD and the center of the crystal on the thermal lens focus are numerically calculated. The thermal lens focus increases along with the increasing array dimensional duty factor and the pumping distance. The result indicates that the evener the pump light distributes along the axis, the smaller the thermal lens affects. It can furnishe evidences for making choice and improving pump resources when axial thermal uniformity is concerned.