Polarization Enhanced Deep Optical Dipole Trapping of $\Lambda$-cooled Polar Molecules

TL;DR

This paper demonstrates a method to efficiently load and cool polar molecules into an optical dipole trap using polarization-optimized $ ext{Lambda}$-cooling, achieving low temperatures and high phase space density.

Contribution

It introduces polarization-enhanced $ ext{Lambda}$-cooling for optical trapping of polar molecules, improving cooling efficiency and trap loading.

Findings

Achieved molecular temperatures as low as 14 μK.

Transferred about 5% of molecules into the trap.

Trap lifetime of approximately 1 second.

Abstract

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