Plasma harmonic emission from laser interactions with dense plasma

A nonlinear procedure is used to account for the mechanism of laser harmonic generation to high orders and plasma emission in laser-dense plasma interactions. A Lagrangian model is used to describe harmonic generation in terms of the oscillatory behavior of an electron plasma. It is shown that the effect of pulse shaping constitutes an important issue for the generation and enhancement of harmonics. It is found that in the presence of electron density 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, plasma emission was observed for the interaction of laser light with super-critical density plasmas with spectral characteristics resembling those found from the fluid model.