A visible helium plasma recombination laser

A small (active volume ≈ 6 cm³), fast Blümlein type, pulsed, transverse-discharge driven laser device exhibited afterglow lasing on the 3s³S-2p³P He transition at 706.5 nm in mixtures of helium and hydrogen or deuterium over a pressure range of 200 mbar. The main features of the laser pulses and relevant time-resolved fluorescence investigations are presented. Population inversion is attributed to the enhanced recombination pumping of upper level population and to hampered lower level population in the presence of H₂ (D₂).