Four level, atomic Cs laser at 852.1 nm with a quantum efficiency above 98%: Observation of three body photoassociation

Lasing on the D2 (6p P23/2→6s S21/2) transition of atomic Cs at 852.1 nm has been observed with a four level system in which the Cs 6p P23/2 state is pumped by the photoassociation and subsequent dissociation of Cs-rare gas collision pairs. Characterized by a quantum efficiency >98%, this laser requires no atomic precursor to the upper laser level and provides oscillation on an alkali transition inaccessible to three level, photopumped alkali laser systems. Measurements of photoabsorption and pump energy threshold in Cs–Ar–Kr mixtures reveal the influence of three body photoassociation.