  Directional infrared emission at 1367 and 5230 nm is generated in Rb vapours
that are step-wise excited by low-power resonant light. The mid-infrared
radiation originating from amplified spontaneous emission on the 5D-6P
transition consists of forward- and backward-directed components with
distinctive spectral and spatial properties. Diffraction limited near-infrared
light at 1367 nm generated in the co-propagating direction only is a product of
parametric wave mixing around the 5P-5D-6P-6S-5P transition loop. This highly
non-degenerate mixing process involves one externally applied and two
internally generated optical fields. Similarities between wave mixing generated
blue and near-IR light are demonstrated.
