The influence of the preplasma on laser induced shockwave in the laser and aluminum-coated planar dielectric target interaction at vacuum has been investigated with the shadowgraphy method. While the laser irradiate on the aluminum-coated dielectric target at intensity of about 1017 W/cm2, the metallic layers absorb laser energy, evaporate and ionize into plasma, it is verified that the scale length of laser-produced plasma is dramatically dependent on the contrast ratio of femtosecond-laser while the main laser pulse energy is almost kept. The characteristics of laser induced shock wave in nanosecond time scale were studied. In the nanosecond time scale, shock wave is only observed in the case of relatively short plasma scale length. This result can be explained by the dissipation of the shock wave during its propagation in the preplasma. In addition, we performed numerical simulation with MULTI2D to get an insight into the propagation of shock wave in the overdense plasma [R. Ramis, J. Meyer-ter-Vehn, and J. Ramírez, Comput. Phys. Commun. 180, 977 (2009)].
Impact of the pulse contrast ratio on molybdenum Kα generation by ultrahigh intensity femtosecond laser solid interaction
