Mode locking in an ion laser at multiple frequencies

An experimental study showed that the average radiation power obtained from a mode-locked argon laser depended nonlinearly on the pulse repetition frequency. Saturation of this dependence was due to the finite value of the relaxation constant of the upper level of the lasing transition in the active medium. The power saturation effect observed under mode-locking conditions at frequencies which were multiples of the intermode spacing was used to determine the lifetimes of the upper levels. The lifetimes were found for the 4p⁴D⁰_5/2 and 4p²D⁰_5/2 levels of the Ar II ion and for the 4p' ¹F₃ and 4p³P₂ levels of the Ar III ion. The results agreed with the published data.