Measurements of Laser-cooled and Trapped Rubidium Atoms

Andrew G. Truscott

H. Ludvigsen, A. Äijälä, A. Pietiläinen +2 more

We have constructed a simplified setup for the demonstration of laser cooling and trapping of rubidium atoms. An external-cavity diode laser was swept across the F = 3 → F' = 2, 3, 4 resonances of the D 2 -line of 85 Rb at 780 nm to resolve the saturated absorption features. Subsequently, the transition F = 3 → F' = 4 was used to cool rubidium atoms in a roomtemperature vapor cell. A cold cloud of trapped atoms with a diameter of approximately 1 mm was produced. The lifetime of the trap was measured to be 1 second.

S. Chakraborty, A. Banerjee, Ayan Ray +4 more

P. L. Chapovsky

Spectral characteristics of rubidium atoms confined in a dark magneto-optical trap (DMOT) are measured, including probe absorption spectra and atom density as a function of the cooling and repumping laser frequencies. The trap can capture and cool more than 2.5 × 10 8 rubidium atoms, confining them in a hyperfine state weakly perturbed by the laser beams used to form the trap. The optical density of the trapped atomic cloud approaches 9. A qualitative model of the DMOT operation is presented, based on the experimental results obtained.

G. Offermans

P. L. Chapovsky

The parameters of a dark magnetooptical trap for rubidium atoms are measured. The rubidium atoms captured and cooled in the trap occupy a hyperfine level of the ground electronic state, which does not interact with cooling laser radiation. The pulsed filling of the trap is produced due to desorption of rubidium caused by irradiation by a short (1 ms) light pulse. The trap captures and cools 2.5 × 10 8 rubidium atoms approximately for 0.2 s. The absorption spectra of a weak probe field by cold atoms are obtained, which demonstrate a good spectral resolution of the hyperfine structure in the excited state. This structure is completely hidden by the Doppler broadening in rubidium vapours at room temperature.