Absorption properties of graphene quantum dots under ultrashort optical pulses

We study the interaction of graphene quantum dots (GQDs) with ultrashort and strong optical pulses theoretically. An important characteristic of such interaction is the energy accumulated by GQDs after the pulse. We show that the GQD absorbance has a highly nonlinear dependence on the field amplitude. At small-field amplitudes, the absorbance strongly depends on the frequency of the pulse and the band gap of a QD, i.e., its size. At large-field amplitudes, $\ensuremath{\sim}1$ V/\AA{}, the absorbance has a weak nonmonotonic dependence on the size of the dot with its maximum value of $\ensuremath{\approx}4.5$% realized for GQD consisting of $\ensuremath{\approx}60$ atoms. As a function of the field amplitude, the absorbance also has a maximum, the position of which depends on the size of the dot.