AMPLIFICATION OF LASER-BEAMS COUNTERPROPAGATING THROUGH A POTASSIUM VAPOR - THE EFFECTS OF ATOMIC COHERENCE

We observe amplification of a linearly polarized laser beam propagatin g through a Doppler-broadened atomic potassium vapor driven by an inte nse, linear and orthogonally polarized counterpropagating laser beam. The observed gain spectra are well explained by a model that incoporat es only the effects of the coherent driving of the atomic dipole momen t and not atomic recoil. Our results suggest that the recently reporte d observations of amplification and lasing using a laser-driven sodium vapor may not arise from the effects of collective atomic recoil.