Starting from weakly bound Feshbach molecules, we demonstrate a two-photon pathway to the dipolar ground state of bi-alkali molecules that involves only singlet-to-singlet optical transitions. This pathway eliminates the search for a suitable intermediate state with sufficient singlet-triplet mixing and the exploration of its hyperfine structure, as is typical for pathways starting from triplet dominated Feshbach molecules. By selecting a Feshbach state with a stretched singlet hyperfine component and controlling the polarization of the excitation laser, we assure coupling to only a single hyperfine component of the A 1 Σ + excited potential, even if the hyperfine structure is not resolved. Similarly, we address a stretched hyperfine component of the X 1 Σ + rovibrational ground state, and therefore an ideal three level system is established. We demonstrate this pathway with 6 Li 40 K molecules. By exploring deeply bound states of the A 1 Σ + potential, we are able to obtain large and balanced Rabi frequencies for both transitions. This method can be applied to other molecular species.

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We investigate the phase noise properties of our Raman laser system for its application in the coherent ground state transfer of LiK polar molecules and discuss recent improvements.

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