|Ph.D Thesis||Department of Physics|
|Supervisor:||Prof. Akkermans Eric|
|Full Thesis text|
A light beam multiply scattered by a cloud of randomly distributed scatterers leads to a very complex interference, or speckle, pattern. The characteristics of a speckle pattern are usually studied using the average transmitted intensity and the intensity correlation function of the scattered light. In particular, the intensity fluctuations for the case of classical scatterers are given by the Rayleigh law, which states that the root mean square of the transmitted intensity equals its configuration average. In this thesis we study the average and the correlation functions of the transmitted intensity of light multiply scattered by a cold atomic gas. We show that the internal structure of atoms, e.g. Zeeman degeneracy, enhances significantly the intensity correlation. This enhancement results from contributions of the
internal degrees of freedom of the scatterers, that do not contribute to the average intensity. These additional contributions are, however, sensitive to an applied magnetic field which reduces sharply the correlation enhancement. The corresponding behavior of the correlation has a resonant-like shape, and its width is narrower than the one obtained in other related phenomena like the Hanle effect. This may have an experimental significance, since the width of the resonance-like peak is directly related to experiments resolution. The enhanced correlation is also sensitive to the motion of scatterers. This motion leads to a rapid decay of the correlation as a function of time.