  Reabsorption, the multiple scattering of spontaneously emitted photons in
optically thick gases, is a major limitation to efficient optical pumping and
laser cooling in ultracold gases. We report mitigation of reabsorption using
spatial and frequency modulation of laser light illuminating such gases. We
developed a semi-classical model that successfully describes the reabsorption
process when frequency-modulated light is present. It was necessary to extend
the treatment in the model beyond a simple two-atom picture in order to
reproduce our experimental results.
