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Q: Quantenoptik und Photonik
Q 45: Quanteneffekte III
Q 45.1: Talk
Tuesday, March 8, 2005, 14:30–14:45, HU 1072
Nonlinear coherent backscattering of light by a dilute gas of two-level atoms — •Thomas Wellens1,2, Benoît Grémaud1, Dominique Delande1, and Christian Miniatura2 — 1Laboratoire Kastler Brossel, 4 Place Jussieu, 75005 Paris, France — 2Institut Non Linéaire de Nice, 1361 route des Lucioles, 06560 Valbonne, France
We study coherent backscattering of a quasi-monochromatic laser pulse by a dilute gas of two-level atoms. Due to interference between different multiple scattering paths, the average intensity scattered by the disordered sample exhibits a narrow cone in exact backscattering direction, on top of the diffused background. We consider the perturbative regime of weak intensities, where nonlinear effects arise from two-photon scattering processes. In contrast to the case of linear scattering, we find that the nonlinear coherent backscattering cone is formed by the interferenc of three different amplitudes. We derive microscopically founded equations for the coherent and incoherent component of the backscattering signal, and present numerical results showing that the enhancement factor exceeds the linear barrier two in certain frequency windows.