SELF-INDUCED PLANAR AND CYLINDRICAL SPLITTING OF A LASER-BEAM IN SODIUM VAPOR

An almost linearly polarized laser beam focused into a sodium vapor ce ll may split into different patterns ranging from two spots to a spot and a ring of opposite circular polarization. The patterns are control led by static magnetic fields of the order of the earth's field. The b ehavior is explained, allowing for a longitudinal component of the die lectric polarization in the paraxial wave equation. Numerical results reveal the delicate balance between light shift, influence of the magn etic field, and the creation of ground-state orientation by the compet ing polarization components.