Time-domain dynamics of saturation of absorption using multilevel atomic systems

A general multilevel carrier kinetics model is explored to simulate the saturation of absorption in the time-domain. Contrarily to approaches relying upon phenomenological descriptions, in this study, we deal with the saturation through a physics-based model that can predict the realistic temporal dynamics of the entire system. Additionally, the proposed method allows high flexibility and generality for the problems under consideration as it is built on a full-wave three-dimensional time-domain solver that can include nonlinear material dispersion, optical activity, and other effects within a joint multiphysics framework. We discretize all the equations using finite-differences combined with the auxiliary differential equation technique which allows adding polarizations driven by diverse underlying physical mechanisms accounting for multiple material dynamics. With our framework, a plethora of time-resolved spatially-dependent numerical data, which are not attainable otherwise, is becoming accessible, hence enabling a comprehensive understanding of the foundations of the materials physics and empowering accurate optimization of new nonlinear photonic devices.