Quantitative absorption imaging: The role of incoherent multiple scattering in the saturating regime

In this paper, we study the modification of coherent scattering processes in dense ensembles. Using absorption imaging, we experimentally demonstrate that the absorption cross section in dense Rb-87 cold atom ensembles is reduced, with respect to the single-particle response. This reduction is linearly dependent on the optical density and well reproduced by a one-dimensional model of coherent field propagation in an ensemble of quantum two-level systems that self-consistently incorporates multiple scattering contribution. Our model shines light upon the key role of incoherent scattering on the modification of the optical response of dense ensembles and leads to a generalization of the Beer-Lambert law. Our result applies to any effective two-level system ensemble and allows for quantitative and absolute in situ absorption imaging.

Automated summary

In this paper, we investigate the modification of coherent scattering processes in dense ensembles. The reduction of absorption cross section in dense Rb-87 cold atom ensembles is experimentally demonstrated and found to be linearly related to the optical density. A one-dimensional model of coherent field propagation in an ensemble of quantum two-level systems, which incorporates multiple scattering contribution, is proposed to explain this reduction. The role of incoherent scattering on the modification of the optical response of dense ensembles is highlighted, and a generalization of the Beer-Lambert law is presented. This result allows for quantitative and absolute in situ absorption imaging for any effective two-level system ensemble.