Laser cooling techniques: standard and alternated optical molasses

Abstract

The technique of laser cooling, whose basic idea was proposed in 1975 [1], provided the development of many important areas like high-resolution spectroscopy [2], atomic clocks [3] and quantum gases confined in magnetic or optical traps [4,5]. Among the techniques applied to cooling neutral atoms is the optical molasses [6] that will be explored in this work. Here we study the standard molasses and a new alternated molasses configuration, which consists of turning on just one pair of counter-propagating laser beams per cycle, and alternating this pair between the three spatial directions. We analyse the two techniques under the lens of the radiation force, by exploring a semiclassical treatment, in order to obtain the minimum energy attained by each of them at the end of the cooling process. We compare, then, these two cooling techniques, pointing out their advantages.

Optical forces on neutral atoms in the presence of fluctuating laser fields: numerical analysis

“…The number and density of trapped atoms in a vapour-cell Zeeman trap are investigated experimentally and theoretically, and it is shown that this quantity is affected by the laser beam sizes, laser intensities, laser detunings, and magnetic-field gradients [19]. The interaction of neutral atoms with the radiation force in OMs is studied using a semi-classical method of the laser-cooling concept [20]. Particularly, since the magnitude of the repulsive force depends on the laser intensity, the power of rescattered light limits the number of trapped atoms.…”