| Abstract: | When a resonant probe pulse propagates slowly through an EIT medium of hot diffusing atoms, the electromagnetic field exhibits diffusion, in addition to the regular free-space diffraction. The extent of the diffusion depends on the degree of atomic excitation, which is maximal when storage of light is performed. For the latter, the evolution of the atomic coherence is described by the coherent diffusion equation.
We demonstrate two aspects of the interplay between diffusion and light. First, we take advantage of our setup to study the self-similar modes of coherent diffusion, the so called Elegant Gaussian modes. We experimentally demonstrate the self-similar behaviour under diffusion of the Elegant Gaussian modes. This, compared to the generally non-self-similar behaviour of the Standard Gaussian modes, the well-known self-similar modes of diffraction. The second part focuses on our ability to manipulate the probe's propagation through the EIT medium by controlling the pump, via the interactions with the diffusing atoms. We expand previous schemes, in which the pump was limited to a plane-wave, and allow it to have an arbitrary shape. We derive the equations of motion for this scenario, and propose and experiment where the pump causes rotation of a “Ferris Wheel” probe. |
