Wave front dislocations appearance under the laser beam self-action in liquid crystal

Utilizing the Huygens-Fresno principle we calculate the propagation of the distorted light beam after the liquid crystal cell. It is found that with distance increasing we can observe at first the dipole, then the quadrupole and then again the dipole of optical vortices whis unit charge. Thus, the trajectory of zero amplitude resembles a deformed rubber ring symmetrical in the xz-, yz-planes and stretched along z-axis.