Four-wave mixing in one-dimensional optical molasses

We present a detailed calculation of the four-wave-mixing signal from one-dimensional optical molasses, in which atoms are cooled by a pair of counterpropagating, cross-polarized fields. The contributions from both Raman and Rayleigh resonances between the discrete motional bound states and the recoil-induced resonances between the motional continuum states are analyzed. It is shown that the recoil-induced resonances can lead to a narrow central resonance peak in the four-wave-mixing signal with a width given by the transverse residual Doppler width. The calculated Raman sidebands also exhibit an asymmetry in the signal strength, a feature observed in recent experiments.