All-Optical Formation of an Atomic Bose-Einstein Condensate

We have created a Bose-Einstein condensate (BEC) of ${}^{87}\mathrm{Rb}$ atoms directly in an optical trap. We employ a quasielectrostatic dipole force trap formed by two crossed ${\mathrm{CO}}_2$ laser beams. Loading directly from a sub-Doppler laser-cooled cloud of atoms results in initial phase space densities of $\sim 1/200$. Evaporatively cooling through the BEC transition is achieved by lowering the power in the trapping beams over $\sim 2\mathrm{s}$. The resulting condensates are $F=1\mathrm{}$ spinors with $3.5\times {10}^4$ atoms distributed between the $m_F=(-1,0,1\mathrm{})$ states.