空气中飞秒激光等离子体荧光辐射光谱研究

系统地研究了不同聚焦条件下飞秒激光空气等离子体的荧光辐射特性以及空间演化情况.在紧聚焦情况下,由于焦点附近比较高的激光强度以及比较高的电子密度,辐射光谱表现为连续谱和线状原子光谱的叠加.在弱聚焦情况下,辐射光谱主要由很多分子线谱组成,而没有观测到连续谱的产生.还研究了光谱谱线强度随激光传输距离的演化情况,结果显示,光谱谱线的强度变化在一定程度上间接反映了等离子体细丝的演化情况.

The fluorescence feature of plasma induced by femtosecond laser pulses in air

Effects of focusing conditions on femtosecond laser induced plasma fluorescence in air are investigated by using different focal length lenses. Under the tightly focusing condition, the fluorescence spectra are composed mainly of continuous spectrum and line spectra from N and O atoms, which is due to the higher laser intensity and corresponding higher electron density than those in the case of weakly focused laser beam. In the latter case, only line spectra from air molecules are observed. Besides, the intensity of line spectrum as a function of propagation distance is measured, which reveals the evolution of the plasma filaments.