We study theoretically the strong-field absorption of an ultrafast optical pulse by a gapped graphene monolayer. At low field amplitudes, the absorbance in pristine graphene is equal to the universal value of $2.3\%$. Although the ultrafast optical absorption for low field amplitudes is independent of the polarization, linear or circular, of the applied optical pulse, for high field amplitudes, the absorption strongly depends on the pulse polarization. For a linearly polarized pulse, the optical absorbance is saturated at the value of $\approx 1.4\%$ for the pulse's amplitude of $\ge 0.4\mathrm{V}/\AA$, but no such saturation is observed for a circularly polarized pulse. For the gapped graphene, the absorption of a linearly polarized pulse shows a weak dependence on the bandgap, while for a circularly polarized pulse, the absorption is very sensitive to the bandgap.

• Received 13 January 2020
• Accepted 6 April 2020

DOI:https://doi.org/10.1103/PhysRevB.101.165433