Characteristics of unconventional Rb magneto-optical traps

Abstract

We study several new magneto-optical trapping configurations in 87 Rb. These unconventional MOTs all use type-II transitions, where the angular momentum of the ground state is greater than or equal to that of the excited state, and they may use either red-detuned or blue-detuned light. We describe the conditions under which each new MOT forms. The various MOTs exhibit an enormous range of lifetimes, temperatures and density distributions. At the detunings where they are maximized, the lifetimes of the various MOTs vary from 0.1 to 15 s. One MOT forms large ring-like structures with no density at the centre. The temperature in the red-detuned MOTs can be three orders of magnitude higher than in the blue-detuned MOTs. We present measurements of the capture velocity of a blue-detuned MOT, and we study how the loss rate due to ultracold collisions depends on laser intensity and detuning. arXiv:1807.07655v1 [physics.atom-ph]

Toward improved loading, cooling, and trapping of molecules in magneto-optical traps

“…Sub-Doppler heating limits how low T and σ one can achieve in both one-color and two-color molecular redMOTs. Similar behavior was observed in atomic Type-II redMOTs [61], and in previous one-color molecular redMOT simulations [26]. Logically, if sub-Doppler heating is present in a redMOT, then one should be able to achieve sub-Doppler cooling in a blueMOT.…”

“…For Type-I transitions, there is sub-Doppler cooling for red-detuned light [57][58][59], while for Type-II transitions, red detuned light results in sub-Doppler heating [25,60]. Thus, type-II (red-detuned) MOTs, including molecular MOTs, tend to be hotter than Type-I MOTs, as the temperature is dictated by the balance between Doppler cooling and sub-Doppler heating [61]. The sign of the sub-Doppler force is reversed for blue-detuned light; this Type-II 'gray-molasses' cooling has been used to produce T ∼ 10 µK gases of atoms [62][63][64][65][66] and molecules [13,14,67,68].…”

“…The sign of the sub-Doppler force is reversed for blue-detuned light; this Type-II 'gray-molasses' cooling has been used to produce T ∼ 10 µK gases of atoms [62][63][64][65][66] and molecules [13,14,67,68]. In principle, a blue-detuned type-II transition can provide both sub-Doppler cooling and a restoring force; such a 'blueMOT' can be colder and denser than a Type-II 'redMOT' [12,61]. To date, a Type-II blueMOT has only been demonstrated in atoms [12]; later in this paper, we discuss potential implementations in molecular systems (sections 5 and 6).…”

Single-Beam Zeeman Slower and Magneto-Optical Trap Using a Nanofabricated Grating

“…A multiple-length Z-wire magnetic trap [51] could be patterned onto the back of our grating chip; permitting atoms to be pulled closer to the chip surface for chipscale atom interferometers [32,52] or quantum memories [33,34]. The tetrehedral MOT configuration should also be applicable to "type-II" MOTs [53,54], which are used to laser-cool and trap molecules [55,56]. We anticipate that, with suitable modifications to the grating, our system could trap molecules from a buffer gas beam source [57], enabling the development of deployable devices using laser-cooled molecules.…”