Effect of the plasma density scale-length on harmonic generation in laser-plasma interaction

The conversion efficiency of harmonics emitted by laser driven plasma was i nvestigated via PIC (Particle In Cell) simulation. We calculated the effici encies of harmonics generated in plasma with different scale-lengths irradi ated by p-polarized, intense (but still non-relativistic) laser pulses of d ifferent durations. We found that the plasma scale-length plays an importan t role in harmonic generation, but this effect is quite different for diffe rent harmonic order, different pulse duration or different plasma density.