Comparison of an efficient implementation of gray molasses to narrow-line cooling for the all-optical production of a lithium quantum gas

We present an efficient scheme to implement a gray optical molasses for sub-Doppler cooling of Li-6 atoms with minimum experimental overhead. To integrate the D-1 light for the gray molasses cooling into the same optical setup that is used for the D-2 light for a standard magneto-optical trap (MOT), we rapidly switch the injection seeding of a slave laser between the D-2 and the D-1 light sources. Switching times as short as 30 mu s can be achieved, inferred from monitor optical beat signals. The resulting low-intensity molasses cools a sample of N = 9 x 10(8) atoms to about 60 mu K. A maximum phase-space density of rho = 1.2 x 10(-5) is observed. On the same setup, the performance of the GM is compared to that of narrow-line cooling in an ultraviolet (UV) MOT, following the procedure in Sebastian et al. [J. Sebastian, Ch. Gross, K. Li, H. C. J. Gan, W. Li, and K. Dieckmann, Phys. Rev. A 90, 033417 (2014)]. Further, we compare the production of a degenerate Fermi gas using both methods. Loading an optical dipole trap from the gray molasses yields a quantum degenerate sample with 3.3 x 10 5 atoms, while loading from the denser UV MOT yields 2.4 x 10(6) atoms. Where the highest atom numbers are not a priority this implementation of the gray molasses technique yields sufficiently large samples for a comparatively low technical effort.