超短超强激光与薄膜靶作用的光学光谱

Optical spectra from interaction between ultrashort ultraintense laser and foil targets

在SILEX-Ⅰ超短超强激光装置上,研究了30 fs,1.0×1019W/cm2超短超强激光脉冲与薄膜靶作用产生的发射光谱。对于3μm厚的铜靶,在激光沿靶面的镜面反射方向观测到二倍频和3/2倍频光谱,且都发生了红移。由红移量推测出等离子体反射面的后退速度约为2.6×108cm/s。对于200 nm厚CH靶,沿激光传播方向观察到超连续光谱,光谱波长范围从约300 nm延伸至约940 nm。利用MULTI-1D流体程序,模拟了超强激光的预脉冲与薄膜靶相互作用过程,结果表明,预脉冲对预等离子体的密度分布有显著影响,是导致实验观测光谱差异的原因。

The optical spectra from the interaction between a 30 fs,1×10^19 W/cm^2 laser pulse and foil targets on SILEX-Ⅰ are studied.Evident red shifts of the second and three-half harmonic emissions in the specular reflection direction are observed from a 3 μm thick copper target.The recession velocity at the reflection surface is deduced to be 2.6×10^8 cm/s.For the 200 nm thick CH target,a supercontinuum extending from 300 to 940 nm is observed in the direction of laser propagation.The density distribution of plasmas induced by laser prepulse is simulated using MULTI-1D hydrodynamic code.The results show that,laser prepulse has a profound effect on the pre-plasma density distribution of a foil target,which leads to the differences in the observed spectra.