Stimulated hyper-raman adiabatic passage. III. Experiment - art. no. 023404

We report the experimental realization of coherent population transfer from the 2 S-3 state to 2 P-3 finestructure levels of helium, using the techniq ue of hyper-Raman adiabatic passage, in which the pump-laser coupling invol ves a two-photon transition. We discuss the dependence of population transf er upon pump and Stokes detunings, and show that by suitably setting the de tunings one can transfer population efficiently as either a two-step proces s to final states or as a single-step two-photon transition to an intermedi ate state. We use an adiabatic-state picture to interpret these experimenta l results. Since the optimum detuning depends on the pump laser intensity t he transfer efficiency is compromised by the variation of the intensity acr oss the spatial profile of the laser beam. Our experimental data agree well with numerical simulation based on density-matrix equations, including all 15 magnetic sublevels.