  An advanced full-wave time-domain numerical model for reverse saturable
absorption (RSA) is presented and verified against established methods. Rate
equations, describing atomic relaxations and excitation dynamics, are coupled
to Maxwell equations by using a Lorentzian oscillator. These oscillator models
the kinetics-dependent light-matter interaction in the form of averaged
polarizations. The coupled equations are discretized in space and time using a
finite-difference time-domain method which provides a versatile platform to
design complex structures and integrate diverse material models. We believe
that our models are crucial tools enabling for the realization and optimization
of optical limiting and all-optical switching systems.

Optics