Surface oscillations in overdense plasmas irradiated by ultrashort laser pulses - art. no. 205004

The generation of electron surface oscillations in overdense plasmas irradi ated at normal incidence by an intense laser pulse is investigated. Two-dim ensional (2D) particle-in-cell simulations show a transition from a planar, electrostatic oscillation at 2 omega, with omega the laser frequency, to a 2D electromagnetic oscillation at frequency w and wave vector k > omega /c . A new electron parametric instability, involving the decay of a 1D electr ostatic oscillation into two surface waves, is introduced to explain the ba sic features of the 2D oscillations. This effect leads to the rippling of t he plasma surface within a few laser cycles, and is likely to have a strong impact on laser interaction with solid targets.