Polarization Enhanced Deep Optical Dipole Trapping of Λ -Cooled Polar Molecules

Abstract

We demonstrate loading of SrF molecules into an optical dipole trap (ODT) via in-trap $\mathrm{\Lambda }$-enhanced gray molasses cooling. We find that this cooling can be optimized by a proper choice of relative ODT and cooling beam polarizations. In this optimized configuration, we observe molecules with temperatures as low as $14(1)\mu \mathrm{K}$ in traps with depths up to $570\mu \mathrm{K}$. With optimized parameters, we transfer $\sim 5\%$ of molecules from our radio-frequency magneto-optical trap into the ODT, at a density of $\sim 2\times {10}^9{\mathrm{cm}}^{-3}$, a phase space density of $\sim 2\times {10}^{-7}$, and with a trap lifetime of $\sim 1\mathrm{s}$.