Coherent excitation of the 5D5/2 level of ultra-cold rubidium atoms with short laser pulses

We demonstrate the use of stimulated Raman adiabatic passage (STIRAP) for population transfer from the ground state to the 5D_5/2 level (5S_1/2 → 5P_3/2 → 5D_5/2) in laser-cooled ⁸⁷Rb atoms and examine the influence of the time delay between laser pulses, pulse height, pulse duration and frequency detuning from resonance on the efficiency of Rb atom excitation to the 5D_5/2 level. In our experiments, the pulse duration was varied widely (30 — 200 ns), which allowed us to assess the effect of spontaneous decay on the population of the 5D_5/2 level (natural lifetime, 300 ns). We performed numerical calculations with allowance for spontaneous decay from the 5P_3/2 and 5D_5/2 levels and compared the results to experimental data, which allowed the population of the 5D_5/2 level to be determined. The maximum population of the 5D_5/2 level in the region under excitation was 80 % of the total number of rubidium atoms.