Spectroscopy of Superradiant scattering from an array of Bose-Einstein   Condensates
  We theoretically study the superradiant gain and the direction of this coherent radiant for an array of Bose-Einstein condensates in an optical lattice. We find that the density grating is formed to amplify the scattering light within the phase match condition. The scattering spectroscopy in the momentum space can provide a method for measuring the overlap of wavefunction between the neighboring sites, which is related to their inner-site and inter-site coherence. 
Xu Xu, Xiaoji Zhou, and Xuzong Chen