Abstract: | We demonstrate that excited alkali states can be spin-polarized with circularly-polarized optical fields, by means of a transient alkali-rare gas molecular complex. Circularly-polarized alkali D2 line lasers have also been realized, and the ability of the pump optical field ellipticity to control the effective degeneracy of the upper laser level is tantamount to controlling the laser transition gain coefficient. Quantum beating at frequencies up to 73 THz has been observed, and coupled quantum beating has been detected by Parametric Four Wave Mixing (PWFM) when Rb vapor is excited with pairs of 55 fs pulses. Tailoring of the laser spectrum results in 7s-5d5/2 and 8s-6d5/2 quantum beating at 18.225 THz and 10.73 THz, respectively. The interaction between the two state superpositions is observed in both the time and Fourier (frequency) domains
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