All-optical production of a lithium quantum gas using narrow-line laser cooling

Abstract

We have used the narrow $2{S}_{1/2}\ensuremath{\rightarrow}3{P}_{3/2}$ 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 $2{S}_{1/2}\ensuremath{\rightarrow}2{P}_{3/2}$ (D2) transition, and temperatures of $\ensuremath{\sim}$300 $\ensuremath{\mu}$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 $\ensuremath{\mu}$K. Furthermore, we find that the light shift of the uv transition in an optical dipole trap at 1070 nm is small and blueshifted, 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 $3\ifmmode\times\else\texttimes\fi{}{10}^{6}$ atoms in a total cycle time of only 11 s.