  Using Floquet theory and the hierarchy of correlations, we study the
non-equilibrium dynamics of the Mott insulator state in the Fermi-Hubbard model
under the influence of a harmonically oscillating electric field representing
the pump laser. After deriving the associated Floquet exponents, we consider
higher-harmonic generation where the strongest signal is obtained if the
driving frequency equals one third of the Mott gap.
