The slowing down of atoms and the redistribution of atom velocities by the pressure of resonant laser radiation

Vladimir G. Minogin, Yu. V. Rozhdestvenskiǐ

Marek Trippenbach, J. Cooper, Keith R. Burnett

V. I. Balykin, Vladilen S Letokhov, Vladimir G. Minogin +1 more

Vladimir G. Minogin

V. I. Balykin, T V Zueva, Vladilen S Letokhov +1 more

The use of resonant radiation pressure produced by an axisymmetric light field for collimating atomic beams is considered. As an example the possibility is examined of collimating an atomic beam by the light field created by reflecting a plane wave from the inner surface of a metal cone. It is shown that radiation pressure makes it possible to reduce the transverse velocities of an atomic beam to values of order 100 cm/s, which corresponds to an effective temperature on the order of 0.001 K. A method for obtaining collimated beams of cold atoms that is based on combined slowing-down and collimation of atom beams in response to the pressure of resonant laser radiation is examined. 16 references.

Leo W. Hollberg, Steven Chu, John E. Bjorkholm +2 more

Using six optical beams (+ and − directions on three orthogonal axes) tuned slightly to the red of resonance it is possible to cool sodium atoms to a few hundred microkelvin. The cooling occurs because the laser radiation pressure creates a damping force which reduces the atomic velocities to a rms value of ~60 cm/s, determined by random scattering. In this optical molasses, the laser beams propagate in all directions and the light acts as a viscous photon fluid which damps the atomic velocity. The resulting motion of the sodium atoms is diffusive until the atoms reach the edge of the laser beams where they escape. The process of atomic confinement by optical molasses can be modeled as a random walk in a viscous medium with a boundary. For a spherical volume of 0.2 cm3 the resulting confinement time is ~0.1 s for half of the atoms to escape. Direct time-of-flight measurement of the atomic temperature gives ~240 μK, which agrees with predictions of quantum limited cooling by resonance radiation pressure. With confinement times of 0.1 s and temperatures of ~240 μK this method provides a source of atoms sufficiently slow for even the highest resolution optical spectroscopy, collision studies, or optical traps.