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arXiv:1812.09177 · Physical Review A

Cooling all external degrees of freedom of optically trapped chromium atoms using gray molasses

Lucas Gabardos, S. Lepoutre, O. Gorceix, L. Vernac, B. Laburthe-Tolra

Published Feb 4, 2019• 6 citations
arXivHTMLPDF

Abstract

An experimental technique is developed to laser cool the motional and spatial degrees of freedom of chromium atoms leading to a trapped system with high phase-space density. The result is a step forward for studying dipolar quantum gases in the degenerate regime.
DOI
10.1103/physreva.99.023607

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We present new techniques in cooling 39 K atoms using laser light close to the D1 transition.First, a new compressed-MOT configuration is taking advantage of gray-molasses-type cooling induced by blue-detuned D1 light.It yields an optimized density of atoms.Then, we use pure D1 gray molasses to further cool the atoms to an ultra-low temperature of 6 μK.The resulting phase-space density is 2 × 10 -4 and will ease future experiments with ultracold potassium.As an example, we use it to directly load up to 3 × 10 7 atoms in a far detuned optical trap, a result that opens the way to the all-optical production of potassium degenerate gases.
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We report on the realization of sub-Doppler laser cooling of sodium atoms in gray molasses using the D1{D}_{1}D1​ optical transition $(3s\phantom{\rule{0.16em}{0ex}}^{2}S_{1/2}\ensuremath{\rightarrow}3p\phantom{\rule{0.16em}{0ex}}^{2}P_{1/2})$ at 589.8 nm. The technique is applied to samples containing $3\ifmmode\times\else\texttimes\fi{}{10}^{9}$ atoms, previously cooled to $350\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{K}$ in a magneto-optical trap, and it leads to temperatures as low as $9\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{K}$ and phase-space densities in the range of ${10}^{\ensuremath{-}4}$. The capture efficiency of the gray molasses is larger than 2/3, and we observe no density-dependent heating for densities up to ${10}^{11}\phantom{\rule{0.28em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$.
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