Af Molisch

Observation of radiation trapping in a dense Cs magneto-optical trap

Abstract We present an experimental and theoretical investigation of the resonant radiation trapping phenomenon in a magneto-optical trap (MOT) for cesium atoms. We have resonantly excited the 62S1/2(F=4)−62P3/2(F′=5) transition with a probe laser and measured directly its effective radiative lifetime. We compare our experimental data with a model based on an approximate solution of the Holstein equation and with a Monte Carlo simulation of the process. The inadequacy of the standard theory for thermal atomic samples in reproducing the data is pointed out.

Radiation trapping in an alkali-vapor-noble-gas mixture excited by a strong laser pulse

We analyze the nonlinear, non-stationary radiation trapping process in a cell filled with a noble gas and an alkali vapor excited by a short intense laser pulse. We derive analytical approximations for the total density of the excited atoms, and for the radiation emerging from the cell. The considered lineshapes are pure Doppler, Voigt, and pure Lorentzian profiles. We confirm that the emergent radiation can decay faster than with the natural lifetime of the atomic transition. We also show that as we increase the noble gas pressure, the decay of the emergent radiation becomes slower at early times and faster at late times.

Computation of nonlinear radiation trapping in a saturated cesium vapor

Abstract We analyze the temporal evolution of the excited-state distribution in a cesium vapor excited by a strong laser pulse of arbitrary duration. We model this situation with equations that include radiation trapping, saturation, and optical pumping. Both the strength and the temporal behavior of the emergent radiation after the laser is switched off depend on the duration of the laser pulse and on the diameter of the laser beam. The decay time constant of the emergent radiation varies from less than the natural lifetime to several hundred times the natural lifetime for cesium densities varying in the range 20–100°C.