  We adapted a recently proposed framework to characterize the optical response
of interacting electrons in solids in order to expedite its computation without
compromise in accuracy at the microscopic level. Our formulation is based on
reliable parameterizations of Hamiltonians and Coulomb interactions, which
allows economy and flexibility in obtaining response functions. It is suited to
computing the optical response to fields of arbitrary temporal shape and
strength, to arbitrary order in the field, and natively accounts for excitonic
effects. We demonstrate the approach by computing the frequency-dependent
susceptibilities of MoS2 and hexagonal BN monolayers up to the third-harmonic.
Grounded on a generic non-equilibrium many-body perturbation theory, this
framework allows extensions to handle generic interaction models or to describe
electronic processes taking place at ultrafast time scales.
