Polarization oscillations of coupled laser beams in an optically pumped atomic vapour

R. Holzner, S. Dangel

Circularly polarized laser beams propagating through sodium vapour and tuned to the buffer-gas-broadened atomic transition can optically pump sodium atoms into a non-absorbing ground state. This causes an intensity-dependent refractive index gradient along as well as transverse to the laser beam propagation direction, giving rise to a number of nonlinear spatio-temporal 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 suitable magnetic fields are applied and the deflection of a beam by the inhomogeneous transverse magnetic field of a current-carrying wire. When two beams of opposite circular polarization are superimposed, astonishing effects such as the mutual deflection of both beams (beam bouncing), the mutual extinction of both beams (beam switching), the separation of initially overlapping beams (beam splitting) and the mutual attraction of both beams (beam attraction) can be observed. While most of the effects can be well described for the stationary state by a to atomic transition model, the correct description of the dynamics requires the consideration of all hyperfine states.

Daniel J. Gauthier, Olivier Pfister, William J. Brown +1 more

Kōichi Shimoda

G.H.C. New, W.T. Welford

Laser beams of opposite circular polarization which travel along adjacent (but not overlapping) paths in sodium vapour, appear to 'repel' each other when the frequency of the light is just above that of the D 1 transition. This effect, which has recently been demonstrated by A C Tam and W Happer (see Phys. Rev. Lett. 1977 38 278–82), can be understood in terms of the optical pumping of the sodium atoms by the respective radiation fields.

Kōichi Shimoda

Chris J. Vale

This thesis presents a study on the realisation of a usable rubidium atomic beam inside a sealed vapour cell. A velocity selective optical pumping scheme was implemented to enable the detection of atoms of a particular velocity class travelling between two separated laser beams. This represents a new spectroscopic technique, the usefulness of which has been demonstrated through its applications. In the present work, the vapour cell atomic beam has been used to measure Larmor precession of polarised atoms in a magnetic field and one-dimensional laser cooling.