Manipulation of a Large Magneto-Optical Trap: application to Four-Wave Mixing
Year: 2008
Type: dissertation
Abstract: In this thesis we present a detailed experimental investigation of size- and densityscaling laws for large Magneto-Optical Traps (MOT) with up to 10^10 atoms. It is well known that laser-induced interactions, produced by multiple scattering, is the main limitation to spatial densities in a MOT. We therefore realized a ?Dark MOT? combined with a Dipole-Trap. Thus, the repulsions were considerably lower and an increase by two factor of magnitude (up to 10^12 atm/cm^3) has been observed. We also propose a qualitative model for the density (and thus for the size), which introduces the mechanical interactions induced by the repumper photons when its optical thickness becomes important. This work is part of the research project to observe Anderson localization of light in cold atoms, where densities of the order of (10^13 - 10^14 atm/cm^3) are required. For densities lower than this critical value gain mechanisms could be useful to amplify prelocalized modes. We thus implemented a pump-probe technique suitable for gain production in the atomic sample. In our case, we have been naturally lead to a Four-Wave Mixing (FWM) configuration. A detailed analysis of the properties and characteristics of FWM-signal has been presented, with, in particularly, a clear red-blue asymmetry of FWM-spectrum for high intensities of the pump beams. We explained this asymmetry by the spatial bunching of the atoms in the nodes or antinodes of the strong standing wave of the pump beams.
Source: HAL
Author: G. L. Gattobigio
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W68950666