Abstract

Recently, Lippi et al.¹ and Hemmer et al.² observed amplification of a laser beam propagating through a collection of Doppler-broadened sodium atoms driven by an intense counterpropagating laser beam. The frequency of the laser beams is tuned near the 3S_1/2→3P_1/2(D₂) transition and the beams are linearly polarized parallel to one another. They attribute the gain to an atomic density grating formed by the collective effect of atomic recoil. We recently suggested³ that stimulated emission processes arising from the coherent driving of the dipale moment may also give rise to amplification of the laser beam in a spectral region where the recoil-induced amplification is predicted to occur. These processes, related to the well-known dressed-state resonances, may enhance or interfere with the recoil-induced effects.

© 1997 Optical Society of America