Highly collimated source of cold Rb atoms from a 2-D magneto-optical trap

Sapam Ranjita Chanu, Ketan D. Rathod, Vasant Natarajan A

Jürgen Schoser, Alexander Batär, R. Löw +4 more

We present a two-dimensional (2D) magneto-optical trap (MOT) setup for the production of a continuous collimated beam of cold ${}^{87}\mathrm{Rb}$ atoms out of a vapor cell. The underlying physics is purely two-dimensional cooling and trapping, which allows for a high flux of up to $6\ifmmode\times\else\texttimes\fi{}{10}^{10}$ atoms/s and a small divergence of the resulting beam. We analyze the velocity distribution of the 2D MOT. The longitudinal velocity distribution of the atomic beam shows a broad feature (full width at half maximum $\ensuremath{\simeq}75 \mathrm{m}/\mathrm{s}),$ centered around 50 m/s. The dependence of the flux on laser intensity, on geometry of the trapping volume, and on pressure in the vapor cell was investigated in detail. The influence of the geometry of the 2D MOT on the mean velocity of the cold beam has been studied. We present a simple model for the velocity distribution of the flux based on rate equations describing the general features of our source.

M. L. Miguez, Ph. W. Courteille

Vincent Carrat, Citlali Cabrera-Gutiérrez, Marion Jacquey +3 more

Using a blue detuned laser shaped in a Laguerre-Gaussian donut mode we highly collimate the output of a two dimensional magneto-optical trap. The resulting atomic beam has a 1 mm diameter, its divergence is reduced from 40 down to 3 mrad and the atomic density is increased by a factor of 200. The collimation effect has been studied versus the order of the Laguerre-Gaussian mode (up to 10) and the laser atom frequency detuning (2 to 120 GHz). The 2D-colli-MOT study allows us to determine the best conditions which minimize the atom heating due to residual light absorption and optimize the collimation effect. The 2D-colli MOT could provide a new tool to fill a 3D-MOT using lasers with millimeter range diameters and thus sparing the laser power.

L. Cacciapuoti, A. Castrillo, Marella de Angelis +1 more

Saptarishi Chaudhuri, Sanjukta Roy, C. S. Unnikrishnan

We discuss the implementation and characterization of the source of a slow, intense, and collimated beam of rubidium atoms. The cold atomic beam is produced by two-dimensional magneto-optical trapping in directions transverse to the atomic beam axis and unbalanced Doppler cooling in the axial direction. The vacuum design allows use of relatively low laser power and a considerably simplified assembly. The atomic beam has a high flux of about $2\ifmmode\times\else\texttimes\fi{}{10}^{10}\phantom{\rule{0.3em}{0ex}}\mathrm{atoms}∕\mathrm{s}$ at a total cooling laser power of $55\phantom{\rule{0.3em}{0ex}}\mathrm{mW}$. It has a narrow longitudinal velocity distribution with mean velocity $15\phantom{\rule{0.3em}{0ex}}\mathrm{m}∕\mathrm{s}$ with full width at half maximum $3.5\phantom{\rule{0.3em}{0ex}}\mathrm{m}∕\mathrm{s}$ and has a low divergence of $26\phantom{\rule{0.3em}{0ex}}\mathrm{mrad}$. The high flux enables ultrafast loading of about ${10}^{10}$ atoms into a three-dimensional (3D) magneto-optical trap within 500 ms. The variation of the atomic beam flux was studied as a function of the rubidium vapor pressure, cooling laser power, transverse cooling laser beam length, detuning of the cooling laser, and relative intensities of the cooling beams along the atomic beam axis. We also discuss a detailed comparison of our measurements of the cold atomic beam with a 3D numerical simulation.