Pulsed ac Stark shifts monitored by Raman Ramsey fringes in sodium vapor.

We have employed Raman Ramsey fringes (RRFs) in sodium vapor to measure ac Stark shifts of the hyperfine levels by an off-resonant shift laser pulse. The ac Stark shifts are directly monitored by the RRF peak shifts and are proportional to the power and the pulse width and antiproportional to the detuning frequency of the shift laser. These findings endorse RRFs to be a strong tool for monitoring small pulsed perturbations.

Ultraslow matched-pulse propagation in sodium vapor.

We have observed ultraslow propagation of matched pulses in a parametric amplifying hot sodium vapor. A fractional delay of more than 1 and a gain of 28 have been simultaneously achieved for a probe pulse of width 100 ns, accompanying a conjugate Stokes pulse with similar gain and delay under a strong coupling beam. The results are compared with the preceding work by Boyer et al. [Phys. Rev. Lett. 99, 143601 (2007)].

Parametric oscillation in sodium vapor by using an external cavity.

We report on parametric oscillation in sodium atomic vapor by using an external cavity. Output powers of approximately 56 mW are obtained for both the signal and idler waves with the input coupling power of 290 mW, resulting in a conversion efficiency of 39%. The signal and idler frequencies are either upshifted or downshifted from the coupling frequency by the amount of the Na hyperfine splitting frequency, and the two waves are found to be strongly temporally correlated.