ABSTRACT
In this chapter, I show some most recent developments in plasma
HHG. In particular, I present the results of experimental studies
of HHG in plasmas containing fullerenes using pulses of different
duration and wavelength. We find that the harmonic cut-off is
extended in the case of few-cycle pulses (3.5 fs, 29th harmonic)
compared with longer laser pulses (40 fs, 25th harmonic) at the
same intensity. Our studies also include HHG in fullerenes using
1300 and 780 nm multi-cycle (35 and 40 fs) pulses. For 1300 nm
pulses, an extension of the harmonic cutoff to the 41st order was
obtained, with a decrease in conversion efficiency that is consistent
with theoretical predictions based on wavepacket spreading for
single atoms.
