Geometrical effects in the loading of an optical atom trap

Loading of atoms contained in a magneto-optic trap into an optical trap formed with the focused laser beam from a CO₂ laser is examined. We show that while the loading efficiency is very sensitive to the volume of the optical trap, it is insensitive to the total laser power once a certain threshold is reached. Based on these observations a time-averaged optical atom trap is realized to compensate for the small capture volume of tight traps which are required for efficient evaporative cooling. Up to a 100% increase in the trap population is observed for the time-averaged traps. We also study the effect on temperature and trap population of changing a time-averaged optical trap back to a static trap. Our results provide a basis for increasing the number of atoms in Bose-Einstein condensates produced using all-optical techniques and show that a high-power laser is not a prerequisite for such an increase.