OPTICAL-PUMPING-INDUCED RING STRUCTURES OF POLARIZED LASER-LIGHT PROPAGATING THROUGH SODIUM VAPOR

We describe a sensitive technique for observing small transverse modif ications to intensity, phase, and polarization arising in nonlinear pr opagation of a laser beam through an atomic vapor. The technique, whic h in essence is an interferometric one, is based on the use of crossed polarizers that are nearly but not exactly pure circular. Illustrativ e results are presented for cw dye-laser radiation propagating through collisionally broadened atomic sodium that is near resonant to the D- 1 line. Well-defined ring patterns produced by nonlinear interactions are observed at both positive and negative laser detunings.