OPTICAL PUMPING-INDUCED SPATIOTEMPORAL MODIFICATIONS TO PROPAGATION, POLARIZATION AND INTENSITY OF LASER-BEAMS IN SODIUM VAPOR

Circularly polarized laser beams propagating through sodium vapour and tuned to the buffer-gas-broadened atomic D-1 transition can optically pump sodium atoms into a non-absorbing ground state. This causes an i ntensity-dependent refractive index gradient along as well as transver se to the laser beam propagation direction, giving rise to a number of nonlinear spatiotemporal intensity and polarization pattern creating processes. In the case of a single circularly polarized laser beam we have observed self-focusing and defocusing, the transformation of the incident Gaussian beam intensity profiles into ring profiles, a large shift of about 5 GHz of the maximum of the absorption profile when sui table magnetic fields are applied and the deflection of a beam by the inhomogeneous transverse magnetic field of a current-carrying wire. Wh en two beams of opposite circular polarization are superimposed, aston ishing effects such as the mutual deflection of both beams (beam bounc ing), the mutual extinction of both beams (beam switching), the separa tion of initially overlapping beams (beam splitting) and the mutual at traction of both beams (beam attraction) can be observed. While most o f the effects can be well described for the stationary state by a J = 1/2 to J' = 1/2 atomic transition model, the correct description of th e dynamics requires the consideration of all hyperfine states.