三束飞秒激光辐照下铜膜内电子非平衡热输运

首先采用有限元法数值计算了铜膜内的电子温度和晶格温度分布变化，揭示了铜膜内电子非平衡热输运时间随飞秒激光光束参量的变化情况。仿真结果表明，铜膜内的电子非平衡热输运时间会随着泵浦光束数量及脉冲能量密度的增加而增加，并且使用三束飞秒泵浦激光作用时，电子非平衡热输运时间比单脉冲作用时的电子非平衡热输运时间增加了3倍。其次使用三束飞秒激光泵浦的泵浦-探测实验系统进行验证。实验结果表明:通过用具有一定延时的三束飞秒泵浦激光作用铜膜时，铜膜表面的瞬态反射率出现三次突变，使电子非平衡热输运时间得到极大延长，从而大幅度消除激光加工热障，并提高加工的质量、精度和效率。

Non-equilibrium heat transport of electron in Cu films irradiated by three femtosecond laser beams

To observe the changes of electron non-equilibrium heat transport time with the femtosecond laser beam parameters in the Cu films, the electron and the lattice temperature curves were studied based on the finite element method and the experimental testing. The simulation results show that the time of electron non-equilibrium heat transport in Cu films will rise with the increasing of both the pump beams number and the energy density of the pulses. The time of electron non-equilibrium heat transport by three pump beams heating was three times higher than that by the single pump beam heating. These results were verified by three femtosecond laser beams pump-probe experimental system. The experimental results show that the transient reflectivity of the Cu films appear three peaks when the Cu films are irradiated by three pump beams with a certain delay, and the time of electron non-equilibrium heat transport has been prolonged greatly. Consequently, the thermal barrier of the device processing is eliminated and the quality, accuracy and efficiency of the femtosecond laser processing are improved.