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arXiv:2311.00561

Two-colour laser cooling for 40K-87Rb quantum gas mixtures

Yann Kiefer, Max Hachmann, Andreas Hemmerich

Published Nov 1, 2023• 0 citations
arXivHTMLPDF

Abstract

We present an efficient cooling scheme for fermionic $^{40}{\text{K}}$ atoms, using laser light red and blue detuned with respect to the $\mathcal{D}2$ and $\mathcal{D}1$ principle flourescence lines, respectively. The cooling scheme is found to significantly increase the saturation level for loading of a $^{40}{\text{K}}$ magneto-optical trap (MOT), resulting in increased atom numbers or decreased cycle times. While the attainable $^{40}{\text{K}}$ atom number is approximately doubled if exclusively $^{40}{\text{K}}$ atoms are cooled, the scheme is particularly powerful for dual-species MOTs, for example, if $^{40}{\text{K}}$ and $^{87}{\text{Rb}}$ atoms are cooled simultaneously in the same MOT configuration. The typical atom losses due to light-assisted hetero-nuclear collisions between $^{40}{\text{K}}$ and $^{87}{\text{Rb}}$ seem to be reduced giving rise to a threefold improvement of the $^{40}{\text{K}}$ atom number as compared to that in a conventional dual-species MOT, operating merely with $\mathcal{D}2$ light. Our scheme can be a useful extension to most dual-species experiments, aiming to reach simultaneous degeneracy of both species.

DOI
10.48550/arxiv.2311.00561

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We present an efficient cooling scheme for fermionic 40K^{40}\mathrm{K}40K atoms, using laser light red and blue detuned with respect to the D2 and D1 principle fluorescence lines, respectively. The cooling scheme is found to significantly increase the saturation level for loading of a 40K^{40}\mathrm{K}40K magneto-optical trap (MOT), resulting in increased atom numbers or decreased cycle times. While the attainable 40K^{40}\mathrm{K}40K atom number is approximately doubled if exclusively 40K^{40}\mathrm{K}40K atoms are cooled, the scheme is particularly powerful for dual-species MOTs, for example, if 40K^{40}\mathrm{K}40K and 87Rb^{87}\mathrm{Rb}87Rb atoms are cooled simultaneously in the same MOT configuration. The typical atom losses due to light-assisted heteronuclear collisions between 40K^{40}\mathrm{K}40K and 87Rb^{87}\mathrm{Rb}87Rb seem to be reduced, giving rise to a threefold improvement of the 40K^{40}\mathrm{K}40K atom number as compared to that in a conventional dual-species MOT, operating merely with D2 light. Our scheme can be a useful extension to most dual-species experiments, aiming to reach simultaneous degeneracy of both species.
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We demonstrate a novel dual color magneto—optical trap (MOT), which uses two sets of overlapping laser beams to cool and trap 87 Rb atoms. The volume of cold cloud in the dual color MOT is strongly dependent on the frequency difference of the laser beams and can be significantly larger than that in the normal MOT with single frequency MOT beams. Our experiment shows that the dual color MOT has the same loading rate as the normal MOT, but much longer loading time, leading to threefold increase in the number of trapped atoms. This indicates that the larger number is caused by reduced light induced loss. The dual color MOT is very useful in experiments where both high vacuum level and large atom number are required, such as single chamber quantum memory and Bose—Einstein condensation (BEC) experiments. Compared to the popular dark spontaneous-force optical trap (dark SPOT) technique, our approach is technically simpler and more suitable to low power laser systems.
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