Four-Wave Parametric Amplification of Rabi Sidebands in Sodium

Four-wave optical parametric amplification enhanced by the ac Stark effect has been observed, with the use of a dye laser tuned near the $D_2$ line of sodium. This process leads to the generation of sidebands displaced from the laser frequency by the generalized Rabi frequency. Under certain experimental conditions, the emitted radiation is in the form of a cone surrounding the transmitted laser beam. A theoretical model that describes these effects is presented.