脉宽对飞秒激光烧蚀合金影响的数值模拟

Numerical Simulation for Influence of Pulse Duration on Femtosecond Laser Ablation of Alloy

运用结合双温模型的分子动力学模拟方法,研究了飞秒激光与B2结构镍钛合金相互作用的烧蚀机制。采用中心波长为800 nm,能量密度为29.3 mJ/cm2,脉宽分别为50、200、500、1 000 fs激光烧蚀90 nm厚度的靶材,并对靶材底部运用压力传输边界条件,表明传输边界条件能够运用于该数值模拟中。靶材温度、内部压力随时间的演化以及原子位型展示了脉宽对烧蚀行为的影响。结果显示,相同能量密度下,脉宽越大辐照中心处电子峰值温度越低而辐照中心处晶格峰值温度越高,靶材热影响区域也越大。脉宽为200、500、1 000 fs时发生烧蚀现象。

The ablation mechanism of the femtosecond laser ablating B2 type NiTi alloy is studied by the molecular dynamics simulation combined with two-temperature model.The target material thickness of 90 nm is ablated by the laser with the central wavelength of 800 nm,energy density of 29.3 mJ/cm2 and pulse durations of 50,200,500 and 1000 fs.The pressure-transmitting boundary condition for the bottom of the target material is formulated,the result shows that the condition is adapted to the simulation.The temperature and internal pressure with time varying and atomic configuration in the target material show the influences of pulse durations on abla tion process.The result shows that the peak temperature of electron in center irradiation zone is lower,the pulse duration is wider at the same energy density,but the peak temperature of lattice in center irradiation zone is high er,the heat affect zone is greater.The ablation is occurred when the pulse durations are 200,500 and 1 000 fs.