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

We demonstrate loading of SrF molecules into an optical dipole trap (ODT) via in-trap Λ-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)  μK in traps with depths up to 570  μK. With optimized parameters, we transfer ∼5% of molecules from our radio-frequency magneto-optical trap into the ODT, at a density of ∼2×10^{9}  cm^{-3}, a phase space density of ∼2×10^{-7}, and with a trap lifetime of ∼1  s.