Plasma harmonic emission from laser interactions with dense plasma

A nonlinear procedure is used to account for the mechanism of laser harmoni c generation to high orders and plasma emission in laser-dense plasma inter actions. A Lagrangian model is used to describe harmonic generation in term s of the oscillatory behavior of an electron plasma. It is shown that the e ffect of pulse shaping constitutes an important issue for the generation an d enhancement of harmonics. It is found that in the presence of electron de nsity perturbations further harmonics beyond the order that corresponds to the upper shelf plasma density can be excited. Computations were performed for mildly relativistic electrodynamics and time scales where wave breaking effects do not take place. Using particle-in-cell (PIC) simulations, plasm a emission was observed for the interaction of laser light with super-criti cal density plasmas with spectral characteristics resembling those found fr om the fluid model. (C) 2000 American Institute of Physics. [S1070-664X(00) 01205-2].