为实现大尺寸、高储能的Nd: YAG板条激光增益介质模块的高可靠性工作,必须找到合适的封装工艺解决大尺寸无空洞、低热阻界面连接问题和界面低应力、低透射波前畸变问题。在充分了解板条激光增益介质和冷却单元的特性后,选择了延展性好的铟作为焊料,实验得到最佳焊料层厚度,通过改进封装工艺的钎焊技术将这两部分可靠地连接在一起。改进的封装工艺实现了钎焊面积大于40 cm2,空洞率小于0.5%,最大空洞面积小于1 mm2的技术指标,工艺重复性大于90%。通过对焊料层的优化实现了尺寸为150.2 mm×30 mm×2.5 mm板条激光增益介质静态透射波前畸变小于1 μm,成品率优于80%,静态透射波前畸变小于1.5 μm的模块成品率接近100%的技术指标。采用改进封装工艺焊接的单模块Nd: YAG板条激光器稳定输出功率达到4000 W。

Two main problems must be solved in order to obtain a reliable slab laser gain medium module with large size and low wave-front distortion during high power working condition. The first problem is the formation of a large connection area with low thermal resistance and free voids. The second problem is how to get a low stress connection with low transmission wave-front distortion. The indium metal was chosen as a welding material for its outstanding ductile property and its optimal thickness was found through experiments. A reliable connection area greater than 40 cm2 has been established between slab laser gain medium and cooling unit by improved welding technique. The repetitiveness of this improved craft with voids ratio less than 0.5% and voids area less than 1 mm2 is over 90%. The ones whose static transmission wave-front distortion is less than 1 μm of slab laser gain medium with the size of 150.2 mm×30 mm×2.5 mm is over 80%, while those with the static transmission wave-front distortion less than 1.5 μm is nearly 100%. A 4000 W-output Nd: YAG slab laser has been achieved based on improved packaging technology.