Simulation of a picosecond laser ablation plasma

A theoretical model has been developed to simulate plasma formation and evo lution during the early stage of picosecond laser ablation of solids. Surfa ce electron emission was implemented as one boundary condition for plasma d evelopment above the target. The simulation results indicate that a plasma forms, with electron density on the order of 10(20)cm(-3), during the picos econd laser pulse. Laser induced gas breakdown assisted by electron emissio n from the target was found to be the origin of the plasma. In agreement wi th experimental measurements, longitudinal movement of the electrons inside the plasma was suppressed after the laser pulse. The suppression of the pl asma can be attributed to the development of a strong electric field above the target. (C) 2000 American Institute of Physics. [S0003-6951(00)03923-1] .