A QUEST for BEC: An all optical alternative

This dissertation describes investigations into optical dipole traps for neutral atoms formed using a high power CO₂ laser beam. Studies of these quasi-electrostatic traps (QUEST's) culminated in the first creation of a Bose-Einstein condensate (BEC) by an all optical means. Carbon dioxide lasers are well suited to the task of atom trapping since their long wavelength results in an extreme detuning and a trapping field that is independent of the internal state of the atom with a practically negligible scattering rate. As a result they are good candidates for achieving BEC as there is little or no intrinsic heating from the trapping beams themselves.; In this work it was found that high spatial densities and phase space densities could be easily established in CO₂ laser traps, giving rise to the possibility of evaporative cooling to the BEC transition. To achieve this a trap was constructed in which it was possible to achieve densities an order of magnitude higher than previously obtained by earlier workers. BEC was subsequently achieved by a forced evaporation procedure in which the highest energy atoms are removed from the trap by adiabatically lowering the trap depth. As the technique involves the most basic of laser cooling and trapping methods, it provides a simple alternative to the standard method of achieving BEC in magnetic traps today.