Toward Creation of an Ultracold Dense Gas of Polar Molecules

We present experimental efforts toward the creation of ultracold gas of KRb polar molecules. We start by creating extremely weakly bound molecules using a magnetic-field Feshbach resonance. This ultracold dense sample of Feshbach molecules provides a starting point for coherent optical transfer schemes aimed at creating tightly bound, polar molecules. Starting with Feshbach molecules, we have performed two-photon and one-photon spectroscopy. We have also demonstrated coherent optical transfer of Feshbach molecules to a more deeply bound state in the electronic ground state. We will discuss suitable routes to extend this work to even more deeply bound vibrational levels where the molecules can have a significant electric dipole moment.