飞秒激光致双液滴光学击穿和等离子体分布研究  

Optical breakdown and plasma morphology distribution of double droplets induced by femtosecond laser

作　　者：钱天 陆健[1] 唐懋 张冲[1] 张宏超[1] QIAN Tian;LU Jian;TANG Mao;ZHANG Chong;ZHANG Hongchao(School of Science,Nanjing University of Science and Technology,Nanjing 210094,China)

机构地区：[1]南京理工大学理学院,南京210094

出　　处：《激光技术》2023年第2期193-199,共7页Laser Technology

基　　金：国家自然科学基金资助项目(11774176)。

摘　　要：为了研究超短激光脉冲与双液滴相互作用过程中的光学击穿和等离子体分布,基于麦克斯韦方程组和电离速率方程,构建了飞秒激光与双液滴的瞬态耦合模型,使用有限元分析方法,对飞秒激光辐照微米量级双液滴的自由电子密度和光场分布进行了计算,得到了双液滴结构对液滴光学击穿和等离子体变化的影响。结果表明,第2个液滴的击穿阈值约为同等条件下单液滴击穿阈值的35%;等离子体的形态和击穿点的位置随双液滴间距发生变化,且在聚焦区域产生纳米等离子体射流;第2个液滴对激光能量的吸收随着双液滴间距的增加而减少;当分别使用满足击穿阈值的光强入射,双液滴吸收的能量约为单液滴的3%;第2个液滴对激光能量的吸收随光强增大而增大,能量吸收比例最终趋于0.01,仅为单液滴的1.5%。该研究为激光诱导水击穿和激光在大气中的传输提供了一定的参考。In order to investigate the optical breakdown and plasma distribution during the interaction between ultrashort laser pulses and double droplets,based on the nonlinear Maxwell’s equations and the ionization rate equation,a transient coupled model of femtosecond laser and double droplets was constructed by finite element analysis.The free electron density and laser field distribution of micron-sized double droplets irradiated by femtosecond laser were calculated,and the effects of double-droplet structures on droplet optical breakdown and plasmonic changes were obtained.The results show that the breakdown threshold of the second droplet is approximately 35%of that of a single droplet under the same conditions.The plasma morphology and the location of the breakdown point vary with the distance between the double droplets,and a nanoplasma jet is generated in focused region.In addition,the absorption of laser energy by the second droplet decreases with increasing distance between the double droplets.The energy absorption of the double droplets is about 3%of that of the single droplet when incident with both laser intensity satisfying their breakdown threshold.The absorption of laser energy by the second droplet increases with the increase of laser intensity,and the energy absorption ratio eventually tends to 0.01,which is only 1.5%of that of a single droplet.The investigation provides a certain reference for laser-induced water breakdown and the transmission of laser in the atmosphere.

关 键 词：大气光学 双液滴 光学击穿 激光等离子体 能量损耗 

分 类 号：O437.5[机械工程—光学工程]