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
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摘要: 在SILEX-Ⅰ超短超强激光装置上，研究了30 fs,1.0×1019 W/cm2超短超强激光脉冲与薄膜靶作用产生的发射光谱。对于3 μm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2.6×108 cm/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。Abstract: The optical spectra from the interaction between a 30 fs, 1×1019 W/cm2 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 2.6×108 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.
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