Investigation of Cooperative Subradiance in Dense Ultracold Rubidium Ensembles

This dissertation presents results of an experimental investigation of the time resolved fluorescence from a cold and dense ensemble of 87Rb atoms after the sample is illuminated by a short probe pulse. The goal of the experiment was to investigate cooperative subradiant behavior, characterized by a much longer decay time compared to the natural lifetime, induced in an off resonant probe regime. Such long lived states, if controllable, would provide a means to store quantum information. The samples were initially created in a magnetooptical trap before atoms were loaded into a far off resonance trap to achieve atomic densities of ≈ 1014 atoms/cm3. The off-resonant temporal response due to a 4 ns probe pulse was the main focus of the investigation, where the probe was blue-detuned 50 − 295 MHz from the 5S1/2 F = 2 → 5P3/2 F′ = 3 transition. Furthermore, by using a short probe pulse, we were able to probe the response outside of the typically explored steady state regime. Our results demonstrate subradiant behavior that is well described by the weak field coupled dipole model.