  This paper focuses on investigating high-order harmonic generation (HHG) in
graphene quantum dots (GQDs) under intense near-infrared laser fields. To model
the GQD and its interaction with the laser field, we utilize a mean-field
approach. Our analysis of the HHG power spectrum reveals fine structures and a
noticeable enhancement in cutoff harmonics due to the long-range correlations.
We also demonstrate the essential role of Coulomb interaction in determining of
harmonics intensities and cutoff position. Unlike atomic HHG, where the cutoff
energy is proportional to the pump wave intensity, in GQDs the cutoff energy
scales with the square root of the field strength amplitude. A detailed
time-frequency analysis of the entire range of HHG spectrum is presented using
a wavelet transform. The analysis reveals intricate details of the spectral and
temporal fine structures of HHG, offering insights into the various HHG
mechanisms in GQDs.
