飞秒激光烧蚀血管支架材料的数值模拟

摘要

为了研究飞秒脉冲激光烧蚀血管支架材料的特性,利用考虑了电子之间热传导项的双温模型,采用有限差分法,对飞秒激光烧蚀NiTi合金的温度场分布进行数值模拟,计算得到了电子温度和晶格温度随时间和烧蚀深度的变化规律,进一步讨论了不同激光能量密度、不同激光脉宽、不同延迟时间对电子和晶格的温度场影响.发现血管支架材料在飞秒激光的作用下,先是电子吸收能量温度快速升高,再通过电声耦合作用将能量传递给晶格,最后两者的温度达到一个平衡状态;激光能量密度主要影响电子的峰值温度和电子与晶格的平衡温度;脉冲宽度主要影响电子的峰值温度和达到峰值温度所用的时间;电子温度随着延迟时间的增加先升高后降低,晶格温度随着延迟时间的增加不断上升.这些理论分析对实际飞秒激光加工血管支架有重要的指导意义.%In order to study the characteristics of femtosecond laser ablation of stent material,two-temperature model which considers the thermal conduction between the electronics,and finite difference method were used to simulate temperature field of NiTi alloys during femtosecond laser ablation.According to the results,the influences of laser energy density,pulse width and delay time on the temperature field of electron and lattice were discussed.The results showed that the temperature of electron and lattice finally reached a state of equilibrium.Before that,firstly,the temperature of electron increased rapidly due to energy absorption,then,the absorbed energy was transferred to lattice through electron phonon coupling effect;at last,the equilibrium would be reached.Laser energy density played a major role in the equilibrium temperature,and pulse width determined the peak temperature and the time to reach it.Consequently,the temperature of electrons first increased and then decreased with the increase of the delay time,but lattice temperature only increased with the increase of the delay time.The results may have an important guiding significance to actual processing of femtosecond laser ablation of vascular stent.