Time-resolved spectroscopy of collinear femtosecond and nanosecond dual-pulse laser-induced Cu plasmas

摘要

In this paper,we investigate the time-resolved spectroscopy of collinear femtosecond(fs)and nanosecond(ns)dual-pulse(DP)laser-induced plasmas.A copper target was used as an experimental sample,and the fs laser was considered as the time zero reference point.The interpulse delay between fs and ns laser beams was 3μs.First,we compared the time-resolved peak intensities of Cu(I)lines from Cu plasmas induced by fs+ns and ns+fs DP lasers with collinear configuration.The results showed that compared with the ns+fs DP,the fs+ns DP laser-induced Cu plasmas had stronger peak intensities and longer lifetimes.Second,we calculated time-resolved plasma temperatures using the Boltzmann plot with three spectral lines at Cu(I)510.55,515.32 and 521.82 nm.In addition,time-resolved electron densities were calculated based on Stark broadening with Cu(I)line at 521.82 nm.It was found that compared with ns+fs DP,the plasma temperatures and electron densities of the Cu plasmas induced by fs+ns DP laser were higher.Finally,we observed images of ablation craters under the two experimental conditions and found that the fs+ns DP laser-produced stronger ablation,which corresponded to stronger plasma emission.