All-Optical Production of a Lithium Quantum Gas Using Narrow-Line Laser Cooling

TL;DR

This paper demonstrates an all-optical method to produce a quantum degenerate lithium Fermi gas using narrow-line ultraviolet laser cooling, achieving lower temperatures and faster cycle times than traditional methods.

Contribution

It introduces the use of a narrow UV transition for laser cooling and trapping lithium, enabling lower temperatures and more efficient production of quantum degenerate gases.

Findings

Achieved MOT temperatures as low as 59 μK.

Demonstrated efficient loading into optical dipole traps.

Produced a quantum degenerate Fermi gas with 3 million atoms in 11 seconds.

Abstract

We have used the narrow $2S_{1/2} \rightarrow 3P_{3/2}$ transition in the ultraviolet (uv) to laser cool and magneto-optically trap (MOT) $^6$Li atoms. Laser cooling of lithium is usually performed on the $2S_{1/2} \rightarrow 2P_{3/2}$ (D2) transition, and temperatures of $\sim$300 $\mu$K are typically achieved. The linewidth of the uv transition is seven times narrower than the D2 line, resulting in lower laser cooling temperatures. We demonstrate that a MOT operating on the uv transition reaches temperatures as low as 59 $\mu$K. Furthermore, we find that the light shift of the uv transition in an optical dipole trap at 1070 nm is small and blue-shifted, facilitating efficient loading from the uv MOT. Evaporative cooling of a two spin-state mixture of $^6$Li in the optical trap produces a quantum degenerate Fermi gas with $3 \times 10^{6}$ atoms a total cycle time of only 11 s.