New atom trap configurations in the near field of laser radiation

В. В. Климов, Vladilen S Letokhov

Pradip Narayan Ghosh

This chapter discusses effective application of low power laser radiations for cooling and use of magnetic field gradient for trapping the atoms. It also discusses the basic principle of operation of Magneto-Optic Traps. Schawlow first showed in the seventies that the optical force of laser radiation can be used to decelerate an atom. This can be accomplished by the absorption of a photon by an atom through a process of stimulated absorption if the laser radiation has a frequency resonant with the energy level difference of the atom. Atoms can be trapped by static magnetic field or a combination of magnetic fields in multipolar, Helmholz or anti-Helmholz configuration or Joffe configuration. Since the atom beams are coherent in nature any beam of atoms from a Bose Einstein condensate can act like an atom laser having high energy that will have very strong penetrating power because of the coherent character of the beam.

Jean Dalibard, Serge Reynaud, Claude N. Cohen-Tannoudji

In the process of cooling and trapping neutral atoms, the authors investigate a new laser configuration, which consists of two counterpropagating laser beams with orthogonal sigma + and sigma - polarisations. They show that such a configuration looks more promising than an ordinary standing wave (where the two counterpropagating waves have the same polarisation), and they explain this result as being due to angular momentum conservation which prevents any coherent redistribution of photons between the two waves. The authors' conclusions are based on a quantitative calculation of the various parameters (potential depth, friction coefficient, diffusion coefficient) describing the mean value and the fluctuations of the radiative forces experienced, in such a laser configuration, by an atom with a J=0 ground state and a J=1 excited state.

Nikolai B. Delone, В. П. Крайнов

V. S. Letkhov, Vladimir G. Minogin

Vladimir G. Minogin

A theory of atomic motion in arbitrary resonant laser fields is put forward. It is shown that when the natural line width of an atomic transition is greater than the recoil energy, the microscopic equations for the atomic density matrix can be reduced to the Fokker–Planck equation for the atomic distribution function and, in the case of slow atoms, the latter can be reduced to the Smoluchowski equation for the atomic density. The macroscopic Smoluchowski equation is used to find laser field configurations which ensure stable trapping of atoms. An extremely simple radiative atomic trap is described and its main parameters are given.