2D Magneto-Optical Trapping of Diatomic Molecules

Abstract

We demonstrate one- and two-dimensional transverse laser cooling and magneto-optical trapping of the polar molecule yttrium (II) oxide (YO). In a 1D magneto-optical trap (MOT), we characterize the magneto-optical trapping force and decrease the transverse temperature by an order of magnitude, from 25 to 2 mK, limited by interaction time. In a 2D MOT, we enhance the intensity of the YO beam and reduce the transverse temperature in both transverse directions. The approach demonstrated here can be applied to many molecular species and can also be extended to 3D.

New frontiers for quantum gases of polar molecules

“…For example, the current state-of-the-art for the molecular magneto-optical trap (MOT) [27,28,29] In the simplest case, STIRAP involves two lasers: one couples the Feshbach molecule state |f to an excited state |e (which is usually lossy), and another couples |e to a deeply bound state |g .…”

“…For example, the current state-of-the-art for the molecular magneto-optical trap (MOT) [27,28,29] is about 2000 molecules of SrF at ∼ 400 µK [30], corresponding to a phase-space density orders of magnitude smaller than typical atomic alkali MOTs of 10 9 −10 10 atoms at ∼ 10 µK. Many other techniques have also been employed to create cold molecules, such as photoassociation [31], buffer gas cooling [32], Stark deceleration [33,34], and Sisyphus cooling [35]; however, the achieved phase-space densities are all very far from that required for quantum degeneracy.…”

Continuous all-optical deceleration and single-photon cooling of molecular beams

“…One way to circumvent this issue is to apply more lasers to reconnect these dark states to the cycling transition [16]. This approach was recently demonstrated with carefully chosen molecular species [17][18][19], and shows particular promise as a method to reach the ultracold regime for those species. An unfortunate consequence of the dark state repumping schemes utilized with these molecules is that they reduce the total scattering rate with each additional repump.…”

Bichromatic magneto-optical trapping forJ→J,J−1configurations

“…In addition to this weak force, J ′′ = 1/2, 3/2 → J ′ = 1/2 transitions present one or two dark states [9, 10] which leads to experimental difficulties if a stronger confining force is desired. Yet stronger force can be produced by rapidly switching the magnetic field gradient and laser beam polarization on a timescale (typically in the sub-microsecond range which is not a simple experimental task) preventing the adiabatic following of the atomic states as done in reference [3] .In this letter we suggest that efficient magneto-optical forces can be restored in all J ′′ → J ′ cases, even for g ′ = 0, in a very simple way, by simply adding one laser field of opposite polarization with a different detuning. We treat the simplest J → J − 1 case (that * Corresponding author: anne.cournol@u-psud.fr is J ′′ = 1 → J ′ = 0) and J → J case (that is J ′′ = 1/2 → J ′ = 1/2).…”

“…Laser cooling and magneto-optical trapping of atoms typically involves J → J + 1 closed transitions driven by counter-propagating circularly polarized laser fields (J is the total angular momentum). On the contrary laser forces on molecule, a more recent subject despite the pioneer experiments [1,2], typically involve N ′′ = 1 → N ′ = 0 transitions (N is the rotational quantum number) between X 2 Σ(v ′′ = 0) and A 2 Π 1/2 (v ′ = 0) vibronic levels [3][4][5]. Including the electron spin leads to J ′′ = 1/2, 3/2 → J ′ = 1/2 transitions.…”