The connection between superradiance, Mie scattering and the collective Lamb shift

• Grant number: 11/10874-2
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: November 01, 2011
• End date: July 31, 2014
• Field of knowledge: Physical Sciences and Mathematics - Physics - Atomic and Molecular Physics
• Principal Investigator: Philippe Wilhelm Courteille
• Grantee: Romain Pierre Marcel Bachelard
• Host Institution: Instituto de Física de São Carlos (IFSC). Universidade de São Paulo (USP). São Carlos , SP, Brazil
• Associated research grant: 13/07276-1 - CEPOF - Optics and Photonic Research Center, AP.CEPID

Abstract

More than 50 years after Robert Dicke's seminal work on superradiance, the collective scattering of radiation at ensembles of point-like scatterers is still not fully explained. The goal of this post-doctoral research project is to contribute to a better understanding by drawing a formal link between superradiance and the well-known classical phenomenon of Mie scattering from extended objects. These are, a priori, very different phenomena, since the former involves point-like scatterers, e.g.~atoms, while for the latter, a coarse-graining approximation turns the cloud into a smooth medium, and the scattered fields are determined thanks to continuity hypotheses at the object boundaries.In particular, we aim at studying (and predicting) Mie resonances ---an extinction phenomenon appearing for resonant conditions between the particle size and the wavelength--- for atomic clouds with smooth boundaries. The second major goal of this project is to characterize the collective Lamb shift raising in dense atomic clouds. This shift is caused by exchange of virtual photons between atoms interacting collectively with a resonant radiation field. Our calculations will help understanding the impact of these phenomena on cold atomic clouds and assist their experimental investigation by providing hints on the parameter regimes, where clear signatures may be expected.The Grupo de Óptica of the Instituto de Física de São Carlos is currently setting up a new experiment aiming at studying the interaction of ultracold atomic strontium clouds with light. Because of its narrow optical transitions, strontium represents an ideal candidate for studies of collective scattering. The calculations will be performed in close interaction with our experiment, in order to obtain experimental confirmation of our models within the term of the research grant. (AU)