Numerical simulation of spreading effect of collimated laser beam in a atmospheric turbulence

The Slip-Step Method(SSM) was used to simulate the field of the collimated laser beam propagating through the atmospheric turbulence, then three kinds of radii were calculated, which shows that they behavior differently as the distance increases. Finally these radii were compared with the theory results, which verified the validity of the simulation when the distance is comparatively small, on another way the simulation becomes incorrect when the distance is large.