Light amplification related to collective atomic recoil affected by dipole-dipole collision

We have studied a collective atomic recoil laser (CARL) including atomic dipole-dipole (D-D) collisions. The results simulated under some sets of parametric conditions reveal that this interatomic interaction plays a negative role in the laser process due to its noncoherent characteristic for the collective atomic recoil motions, which greatly reduces the spatial orderliness of the atomic density distribution necessary for the laser operation