Probing and manipulation of cold Rubidium atoms in MOT and in dipole trap,

Roger B. M. Clarke, Erling Riis

Sanjukta Roy, Saptarishi Chaudhuri, C. S. Unnikrishnan

We discuss the results of measurements of the temperature and density distribution of cold Rubidium atoms trapped and cooled in an optical dipole trap formed by focussed CO 2 laser beams at a wavelength of 10.6 μ m from a cold, collimated and intense atomic beam of flux 2 × 10 10 atoms/s produced using an elongated 2D + MOT. A large number of rubidium atoms (⩾ 10 10 ) were trapped in the MOT and the number density of atoms were further increased by making a temporal dark MOT to prevent density-limiting processes like photon rescattering by atoms at the trap centre. Subsequently, between 10 7 to 10 8 cold atoms at a temperature below 30 μK were transferred into a Quasi-Electrostatic trap (QUEST) formed by focussed CO 2 laser beams at the MOT centre. Both single beam and crossed dual beam dipole traps were studied with a total output power of 50 W from the CO 2 laser with focal spot sizes less than 100 microns. Various measurements were done on the cold atoms trapped in the dipole trap. The total atom number in the dipole trap and the spatial atom number density distribution in the trap was measured by absorption imaging technique. The temperature was determined from time-of-flight (TOF) data as well as from the absorption images after ballistic expansion of the atom cloud released from the dipole trap. The results from measurements are used to maximize the initial phase-space density prior to forced evaporative cooling to produce a Bose-Einstein Condensate.

Vasily M. Entin, I. I. Ryabtsev

The experimental results of the probe spectroscopy of laser cooled Rb atoms in a magneto-optical trap (MOT) are presented. The absorption spectra of the probe transition were expected to be significantly different, and indications of coherent population trapping were expected for the dark repumping transition.

A. Fioretti, Jérôme Lozeille, Carlo Andrea Massa +2 more

A. Pietiläinen, H. Ludvigsen, Hannu Talvitie +1 more

Nathan Souther

We have measured light shifts, also known as the A.C. Stark effect, in cold Rubidium atoms using pump-probe spectroscopy.The measurement was made both for atoms in a magneto optical trap (MOT) and for atoms that were in an optical molasses.We show that while the measured light shifts agree with theory for optical molasses there are additional Zeeman shifts in the MOT that the theory does not account for.To the best of our knowledge, this is the first time a careful systematic measurement has been performed in cold atoms of light shift as a function of intensity.