为了保证水导激光微细加工中会聚激光与水束光纤的耦合效果,建立了由一个高精度耦合对准检测调整系统和一个特殊结构耦合装置组成的新的耦合系统,并提出了新的耦合对准方法。由于激光要经过空气层、玻璃层、水层进入水束光纤,因此根据计算结果,采用激光烧斑法来确定会聚透镜与水束光纤起始端(喷嘴孔)的距离;研究了激光在水束光纤中发生全反射的最大入射角;通过流体动力学仿真,设计了腔内流场分布均匀的耦合装置,保证了直径0.12 mm的水束光纤的高耦合品质;研究了激光能量在水束光纤中的衰减,采用特定波长和脉冲能量的激光和特殊过滤的去离子水来减小激光能量在水束光纤中耦合的损耗率。实验结果表明,水束光纤导光长度超过100 mm;采用该耦合技术能够在0.2 mm厚的硅基晶片上以2 mm/s速度切割出缝宽为0.12 mm的均匀窄缝,且几乎无裂纹、无热影响区。该耦合技术能够很好地满足水导激光微细加工的要求。

In order to improve the coupling effect of focused laser and waterjet fiber,a new coupling system consisting of an accurate coupling alignment system and a special coupling unit was designed,and a special coupling alignment method also was put forward.Before laser arrives at water-jet fiber,it passes through air,glasses and water,so a laser burning method was used to determine the distance between focus lens and nozzle hole based on calculating result.The max angle of laser incidence was researched for full reflection.After fluid simulation,the coupling unit was designed to make the fluid field in the chamber symmetrcally and form a high quality water-jet fiber with diameter of 0.12 mm.The attenuation of laser energy in water-jet fiber was investigated and the energy attenuation in fiber was reduced applying appropriate laser wavelength,pulse energy and filtered and deionized water.The experimental results indicate that a 100 mm long water-jet fiber is formed in this paper,and an 0.12 mm wide slot without nearly crack and heat affected is cut in 0.2 mm thick Si wafer at the speed of 2 mm/s,which shows proposed coupling technology can meet the requirements for water-jet guided laser micromachining perfectly.