飞秒激光烧蚀硅表面产生等离子体的发射光谱研究

对中心波长为800 nm,脉宽为100 fs的激光脉冲烧蚀空气中硅(111)产生的等离子体发射光谱进行了时间和空间分辨研究. 结果表明,在等离子体羽膨胀初期(小于50 ns时间范围内),等离子体发射光谱主要由连续光谱构成,此后连续光谱强度逐渐减弱,线状光谱开始占主导地位;在羽体膨胀过程中离子谱线的存在时间短于原子谱线的存在时间. 由时间分辨发射光谱发现在羽体膨胀过程中等离子体辐射波长存在红移现象,波长红移量随时间演化呈二次指数衰减. 最后给出等离子体发射光谱谱线强度的时空演化规律. 关键词： 飞秒激光 脉冲激光烧蚀 等离子体 发射光谱

Optical emission spectra of Si plasma induced by femtosecond laser pulse

The time- and space-resolved optical emission spectra (OES) of Si plasma produced by femtosecond laser pulse with center wavelength of 800 nm and pulse width of 100 fs in air were investigated. The results show that the OES mainly consist of continuous spectrum at the early stage of plasma expansion (within the first 50 ns), then the continuous spectrum weakens gradually while the line spectrum becomes dominating. The existence time of ion spectra is shorter than that of atomic spectra in the process of plume expansion. The wavelength red-shift, which has a second order exponential decay with delay time, has been found by the time-resolved emission spectroscopy. Finally, the spatiotemporal evolution of OES intensity are presented.