Suppression of Reabsorption via Modulation of Light

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.