飞秒脉冲激光作用下金属薄膜的热弹性研究  

Study on Thermoelasticity of Metal.Film Induced by Femtosecond Pulsed Lasers

作　　者：王德飞[1] 齐文宗[1] 李瑞锋[2] 

机构地区：[1]四川大学电子信息学院,四川成都610064 [2]昆明冶金高等专科学校自动化与电力学院,云南昆明650091

出　　处：《光学与光电技术》2009年第1期36-40,共5页Optics & Optoelectronic Technology

摘　　要：利用双曲-双温两步热传导和热电子崩力模型,考虑到晶格温度与应变速率的耦合效应,得到了用于描述飞秒激光作用下金属薄膜热力效应的超快热弹性模型。以飞秒脉冲激光辐照金属铜薄膜为例,运用具有人工粘性和自适应步长的有限差分算法,对不同能量密度和脉冲宽度条件下薄膜体内温度场和应力场的变化规律进行了数值模拟,对比分析了电子晶格耦合系数对超快加热过程的影响。结果表明,飞秒脉冲激光辐照早期为明显的非平衡加热过程,电子温度迅速升高,而晶格温度的升高却相对较慢;激光辐照早期的热力耦合效应导致薄膜前表面附近的热应力表现为压应力,随着时间的推移,热应力由压应力转变为张应力,为激光加工和激光对抗提供了理论参考。By means of the dual temperature hyperbolic two-step heat conduction and hot-electron blast force models, considering the coupling effect between lattice temperature and strain rate, an ultrafast thermoelastieity model is derived and used to investigate the thermal-mechanical response of metal films caused by femtosecond pulsed lasers. Taking the copper film as a typical example, the variation law of temperature and stress fields under the conditions of different values of laser fluence density and pulse duration are simulated numerically by using a finite difference scheme with adaptive step-size and artificial viscosity. Comparative analysis of the influence on the ultra-fast heating that calculated with the temperature-dependent coupling coefficient G（Tc, T1） and constant coupling coefficient Gc is also made. It is shown that electron temperature rises rapidly while lattice temperature rises in graduai in the early heating stage, which is an evident non-equilibrium process. In the early heating period, the thermal-mechanical coupling effect results in the compressive stress developed near the heated surface, and then the compressive stress reverses to be tensile stress, which provide a theoretical reference for laser processing and countermeasures.

关 键 词：飞秒脉冲激光 金属薄膜 热应力 非平衡加热 

分 类 号：O487[理学—固体物理] TN249[理学—物理]