Rayleigh superradiance and dynamic Bragg gratings in an end-pumped   Bose-Einstein condensate
  We study experimentally superradiant Rayleigh scattering from a Bose-Einstein condensate (BEC) in a new parameter regime where pump depletion and the exchange of photons between the endfire modes are important. Through experiments and simulations we show that collective atom light coupling leads to the self-organized formation of dynamic Bragg gratings within the sample. These gratings lead to an efficient back-scattering of pump photons and optical resonator structures within the BEC. 
A. Hilliard, F. Kaminski, R. le Targat, C. Olausson, E. S. Polzik, and   J. H. M\"uller