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

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.\footnote{P. M. Duarte et al., Phys. Rev. A \textbf{84}, 061406 (2011).} Laser cooling of lithium is usually performed on the $2S_{1/2}\rightarrow 3P_{3/2}$ (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\footnote{M. Safronova, Personal Communication.}, facilitating efficient loading from the UV MOT. After loading from the UV MOT, $6 \times 10^6$ atoms with peak density $n_0=2.7\times 10^{13} \,{cm}^{-3}$ remain at $T=60\,\mu{K}$, which corresponds to $T/T_{F}\approx2.7$. 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 in only 5~s.