飞秒激光诱导铝等离子体时间分辨光谱研究

在大气环境下利用中心波长800nm、脉宽为30fs的激光聚焦在铝靶上，测定了激光诱导铝等离子体中铝原子的时间分辨发射谱。在局部热平衡条件近似下，根据实验测定的谱线相对强度得到了等离子体的电子温度；研究了激光脉冲能量对等离子体电子温度的影响和等离子体电子温度的时间演化特性。同时，实验发现了394.4nm和396.1nm两条铝原子谱线存在较强的自吸收效应，实验结果表明随着激光脉冲能量的减少和延时的增加，自吸收现象逐渐消失。

An Investigation on the Time-resolved Spectrum of the Femtosecond Laser-induced Al Plasma

The time-resolved spectrum of Al atom in laser-induced Al plasmas was measured by focusing 30 femtosecond laser pulse with wavelength 800nm on Al target in ambient air. Under the approximation of local thermodynamic equilibrium, the electron temperature was calculated from the measured relative intensity of emission spectral line. The influence of laser pulse energy on the electron temperature and the temporal evolution of electron temperature were studied. It is found from the experiment that the self-absorption effection is obvious for the 394.4nm and 396.1nm spectral lines of Al atom. It also can be concluded that the self-absorption of the spectral lines will gradually disappear with the decrease of the laser pulse energys and the increase of the time delay.