RADIATION TRAPPING IN ATOMIC VAPORS IN FINITE-CYLINDER VAPOR CELLS EXCITED BY A LASER-BEAM

We compute radiation trapping in a two-level atomic vapour excited by a laser beam, taking into account saturation effects and using a reali stic vapour-cell geometry, the finite cylinder. By using an approximat ion for the angular distribution of the fluorescence radiation, CPU-ti me requirements are kept low. We then analyse various practical cases and present useful practical rules of thumb when certain simplificatio ns are valid. When we consider the decay of an initial excitation, the decay at late times can be computed by using an equivalent one-dimens ional geometry. For early times, it is usually important to include th e three dimensionality of the problem. Finally, we present calculation s how the 'burn-through' effect of a strong laser affects the approxim ation of the geometry.