Spectroscopy of strong-pulse superradiance in a Bose-Einstein condensate

We study experimentally superradiance in a Bose-Einstein condensate using a two-frequency pump beam. By controlling the frequency difference between the beam components, we measure the spectrum of the backward (energy-mismatched) superradiant atomic modes. In addition, we show that the populations of these modes display coherent time dynamics. These results are compared to a semiclassical model based on coupled Schrodinger-Maxwell equations.