Optical Production of Ultracold Polar Molecules

We demonstrate the production of ultracold polar RbCs molecules in their vibronic ground state, via photoassociation of laser-cooled atoms followed by a laser-stimulated state transfer process. The resulting sample of $X^1{\Sigma }^{+}(v=0)$ molecules has a translational temperature of $\sim 100\mu \mathrm{K}$ and a narrow distribution of rotational states. With the method described here it should be possible to produce samples even colder in all degrees of freedom, as well as other bialkali species.