Loading and high efficiency evaporative cooling to BEC with a MACRO-FORT

We present modeling and experimental results for efficient evaporative cooling in all-optical BEC experiments. By employing a misaligned crossed-beam far off-resonance optical dipole trap (MACRO-FORT [1]) we achieve decreasing trap depth with increasing average trap frequency during the evaporative cooling process, allowing highly efficient runaway evaporation. This method is effective even with a low initial atom density, and it has experimentally allowed us to create BECs of $^{87}$Rb starting from only a few $10^5$ atoms initially in the optical trap before evaporation. We have also studied the direct loading of $^{87}$Rb atoms from a MOT to our 1550nm optical trap, where the atomic D2 transition has a significant AC Stark shift.\\[4pt] [1] J.-F. Clement \textit{et al}., Phys. Rev. A \textbf{79}, 061406(R) (2009)