Coherent scattering of near-resonant light by a dense, microscopic cloud of cold two-level atoms: Experiment versus theory

We measure the coherent scattering of near-resonant light by a cloud of laser-cooled two-level rubidium atoms with a size comparable to the wavelength of light. We isolate a two-level atomic structure by applying a 300 G magnetic field. We measure both the temporal and the steady-state coherent optical response of the cloud for various detunings of the laser and for atom numbers ranging from 5 to 100. To describe our observations, we introduce a multi-mode, paraxial Maxwell-Bloch model valid in the high intensity regime. In the low intensity regime, we compare it to a stochastic coupled-dipole model and find excellent agreement. Comparing to the data, the models are found in better agreement than for previously studied unpolarized, dense samples.