Effective two-level approximation of a multi-level system driven by coherent and incoherent fields

TL;DR

This paper introduces an effective two-level model to simulate the optical response of multi-level atomic systems under various conditions, maintaining computational efficiency while capturing complex scattering behaviors.

Contribution

It presents a novel approach to approximate multi-level systems with a two-level model that accurately reproduces scattering properties across different saturation regimes.

Findings

Model accurately reproduces scattering properties under various experimental conditions.

Effective two-level approximation extends to different polarization and magnetic field scenarios.

Quantified trust interval for 87Rb D2-line, generalizable to other systems.

Abstract

The numerical simulation of multiple scattering in dense ensembles is the mostly adopted solution to predict their complex optical response. While the scalar and vectorial light mediated interactions are accurately taken into account, the computational complexity still limits current simulations to the low saturation regime and ignores the internal structure of atoms. Here, we propose to go beyond these restrictions, at constant computational cost, by describing a multi-level system (MLS) by an effective two-level system (TLS) that best reproduces the coherent and total scattering properties in any saturation regime. The correspondence of our model is evaluated for different experimentally realistic conditions such as the modification of the driving field polarization, the presence of stray magnetic fields or an incoherent resonant electromagnetic field background. The trust interval of the model is quantified for the D2-line of 87Rb atoms but it could be generalized to any closed transition of a multi-level quantum system.