“…At relatively low Rb density (N ≤ 6 × 10 12 cm −3 ), only forwarddirected collimated light at 1.37 μm is generated [13]. However, at higher N collimated emission at 1.32 μm dominates, having been observed in both the co-and counter-propagating directions and attributed to nonparametric ASE on the 6S 1∕2 → 5P 1∕2 transition [14].Appearance of the CBL and near-IR emission at 1.37 μm in only the co-propagating direction suggests a common parametric origin. The lifetimes of the 5D 5∕2 , 6P 3∕2 , and 6S 1∕2 levels (240, 120, and 46 ns, respectively) mean that ASE at 5.23 and 2.73 μm can occur along the pencil-shaped region defined by the applied laser beams.…”