Laser Cooling of Optically Trapped Molecules

TL;DR

This paper demonstrates laser cooling of calcium monofluoride molecules within an optical trap, achieving sub-Doppler temperatures, increased loading efficiency, and high molecular density, advancing molecular quantum control.

Contribution

It introduces a method for laser cooling molecules directly in an optical trap, with enhanced loading and high-density trapping, which was not previously achieved.

Findings

Achieved sub-Doppler cooling to 60 μK.

Loaded 150 molecules into the optical trap.

Trap lifetime dominated by background gas collisions.

Abstract

Calcium monofluoride (CaF) molecules are loaded into an optical dipole trap (ODT) and subsequently laser cooled within the trap. Starting with magneto-optical trapping, we sub-Doppler cool CaF and then load $150(30)$ CaF molecules into an ODT. Enhanced loading by a factor of five is obtained when sub-Doppler cooling light and trapping light are on simultaneously. For trapped molecules, we directly observe efficient sub-Doppler cooling to a temperature of $60(5)$ $\mu\text{K}$. The trapped molecular density of $8(2)\times10^7$ cm$^{-3}$ is an order of magnitude greater than in the initial sub-Doppler cooled sample. The trap lifetime of 750(40) ms is dominated by background gas collisions.