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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。
In the SILEX-Ⅰ ultrashort superlattice laser device, the emission spectra of ultrashort super laser pulses of 30 fs and 1.0 × 10 19 W / cm 2 were studied. For the 3μm-thick copper target, the second harmonic and 3/2 octave spectra were observed in the specular reflection direction of the laser along the target surface, and both red shifted. The retreating speed of the plasma reflecting surface was estimated to be about 2.6 × 108 cm / s from the amount of redshift. For a 200 nm thick CH target, a supercontinuum is observed along the laser propagation direction, with spectral wavelengths extending from about 300 nm to about 940 nm. The MULTI-1D fluid program was used to simulate the pre-pulse interaction between the super-laser and the thin film target. The results show that the pre-pulse has a significant effect on the density distribution of the pre-plasma, which is the reason for the difference of the observed spectra.