Simultaneous sub-Doppler laser cooling of fermionic ${}^6$Li and ${}^{40}$K on the D${}_1$ line: Theory and Experiment

Abstract

We report on simultaneous sub-Doppler laser cooling of fermionic ${}^6$Li and ${}^{40}$K using the D${}_1$ optical transitions. We compare experimental results to a numerical simulation of the cooling process applying a semi-classical Monte Carlo wavefunction method. The simulation takes into account the three dimensional optical molasses setup and the dipole interaction between atoms and the bichromatic light field driving the D${}_1$ transitions. We discuss the physical mechanisms at play, we identify the important role of coherences between the ground state hyperfine levels and compare D${}_1$ and D${}_2$ sub-Doppler cooling. In 5 ms, the D${}_1$ molasses phase largely reduces the temperature for both ${}^6$Li and ${}^{40}$K at the same time, with a final temperature of 44 $\mu$K and 11 $\mu$K, respectively. For both species this leads to a phase-space density close to $10^{-4}$. These conditions are well suited to directly load an optical or magnetic trap for efficient evaporative cooling to quantum degeneracy.

12 pages, 11 figures; submitted to Phys. Rev. A; V2 contains edits in response to referee's comments

References in corpus (3)

• Efficient all-optical production of large ${}^6$Li quantum gases using D${}_1$ gray-molasses cooling
• 2.1-watts intracavity-frequency-doubled all-solid-state light source at 671 nm for laser cooling of lithium
• Two-stage magneto-optical trapping and narrow-line cooling of ${}^6$Li atoms to high phase-space density

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• Narrow-linewidth cooling of ${}^6$Li atoms using the 2S-3P transition
• Cross-dimensional relaxation of ${}^7$Li-${}^{87}$Rb atomic gas mixtures in a spherical-quadrupole magnetic trap
• Cooling All External Degrees of Freedom of Optically Trapped Chromium Atoms Using Gray Molasses