Population transfer in cw-excited Rb resulting from mirrorless maser oscillation.

Abstract

A dense atomic Rb beam, excited by three cw lasers to the 10${\mathit{F}}_{7/2}$ state, is found to contain substantial population in the 11${\mathit{D}}_{5/2}$ state, which lies 75 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ lower in energy. The mechanism for the population transfer is determined to be maser oscillation at the 10F-11D transition frequency, self-sustaining even in the absence of mirrors, which saturates the populations of the two levels. Although the maser radiation is not observed, the population levels and threshold conform to a simple rate equation model.