Quantum optical processes in a magneto-optical trap with a small number of atoms

Swarupananda Pradhan, S. J. Gaur, K. G. Manohar +1 more

We demonstrate enhancement in the number of trapped cesium atoms in a magneto-optical trap (MOT) using a control laser that illuminates only a small faction of the capture region of the trap without interacting with the cold cloud of atoms. The enhancement is maximized when the laser is slightly blue detuned with respect to the cooling transition. Trap loading curves point to approximately a twofold increase in the capture rate, which as a consequence results in the increase in the steady state number of trapped atoms. Enhanced loading is confirmed by MOT loading and decay curves taken under the modulation of the control laser beam. Optical pumping of the inaccessible Zeeman states into the stretched states is suggested as a possible mechanism.

S. aus-der-Wiesche, B. Ueberholz, Frank Strauch +2 more

Gregory W. Hoth, Elizabeth A. Donley, John E. Kitching

We measure the number of atoms N trapped in a conventional vapor-cell magneto-optic trap (MOT) using beams that have a diameter d in the range 1-5 mm. We show that the N is proportional to d(3.6) scaling law observed for larger MOTs is a robust approximation for optimized MOTs with beam diameters as small as 3 mm. For smaller beams, the description of the scaling depends on how d is defined. The most consistent picture of the scaling is obtained when d is defined as the diameter where the intensity profile of the trapping beams decreases to the saturation intensity. Using this definition, N scales as d(6) for d<2.3 mm but, at larger d, N still scales as d(3.6).

Luís Gustavo Marcassa, Gregory I. Surdutovich, Marcos Oriá +4 more

Tomasz Brzozowski

Yanhua Wang, Yang Hai-Jing, Tiancai Zhang +2 more

The number of cold atoms trapped in magneto-optical trap(MOT) can be derived from probe absorption signal. After the MOT is switched off, the cold cloud freely expands in gravitational field with an initial velocity distribution. So the measurement process can be described with the interaction model between the individual stationary two-level atom and single mode resonate laser. Absorption method can largely improved the measurement precision. In this paper we introduce the physical principle of measurement and demonstrate the whole experimental procedure in detail. The number of atoms trapped in our MOT, (8±0.3)×106 is measured in experiment. And the number of steady-state atoms and the lifetime of atom trapped in MOT was used to deduce the capture rate of MOT.