Beating the density limit by continuously loading a dipole trap from millikelvin-hot magnesium atoms

Abstract

We load 10 5 magnesium atoms in a dipole trap from a millikelvin-hot magneto-optical trap (MOT) using a continuous-loading scheme. Light-assisted two-body processes limit the maximum achievable density in a MOT, resulting in a reduced transfer efficiency into a dipole trap when using the conventional sequential scheme. It is overcome in a continuous-loading scheme where a loss channel is opened in the MOT. This allows the accumulation of atoms in the dipole trap over the trap lifetime, determined by collisions with the background gas. This results in a significantly higher number of trapped atoms even at a lower steady-state peak density in the MOT.

Midinfrared magneto-optical trap of metastable strontium for an optical lattice clock

“…To address this need, efficient methods of laser cooling alkaline earth metals have already been developed in the pioneering work of several groups over the past few decades [10][11][12][13][14]. In this report, we add to this body of work by demonstrating a metastable magnetooptical trap (MOT) for strontium based on the transition between the 5s5p 3 P 2 and 5s4d 3 D 3 states separated by 2.92 µm (see Figure 1), a cycling transition similar to that used previously to create metastable MOTs for calcium [15] and magnesium [16]. We show that the metastable MOT for strontium reaches a final temperature of 6 µK, and that the same transition at 2.92 µm can be used to prepare spin-polarized samples of cold 87 Sr atoms in an optical lattice for realizing a high-precision optical clock.…”

“…We use the mid-infrared transition to prepare 87 Sr atoms in a spin polarized state in a magic-wavelength optical lattice for high-precision spectroscopy of the 5s 2 1 S 0 to 5s5p 3 P 0 clock transition. The metastable MOT results in comparable loading time and atom number as alternative cooling methods for optical lattice clocks [38,39], and achieves a lower temperature than metastable MOTs previously realized in calcium [15] and magnesium [16] by an order of magnitude.…”

New approaches in deep laser cooling of magnesium atoms for quantum metrology

“…At the same time, it is necessary to cool atoms down to several microkelvins. This problem can be solved by the velocity-selective cooling as in [5,6]. At that, the special conditions must be satisfied before the velocityselective cooling stage to save the most of ultracold atoms in a cloud.…”

“…In the recent experiments [5,6] researchers managed to obtain magnesium atoms owing temperature about several microkelvins and confined them in the lattice. However, velocity-selecting cooling technique in a shallow dipole trap was applied immediately after the magneto-optical trap stage (MOT), which led to great loss in number of atoms (~ 0.01% from the initial number in the MOT).…”

“…Our theory analyzes the dipole transition 3 3 P 2 →3 3 D 3 (λ≈383.3 nm), which was also used in the experiments by our colleagues from Hanover [5,6]. Basing on the numerical calculations we try to understand the origins of the existing difficulties.…”