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arXiv:2401.08286 · Physical Review A

Continuous loading of a magneto-optical trap of Rb using a narrow transition

Rajnandan Choudhury Das, Thilagaraj Ravi, Samir Khan, Kanhaiya Pandey

Published Jun 10, 2024• 7 citations
arXivHTMLPDF

Abstract

We report continuous loading of $^{\text{87}}\mathrm{Rb}$ atoms in a magneto-optical trap (MOT) at narrow linewidth, 420-nm $5{S}_{1/2}$, $F=2\ensuremath{\rightarrow}6{P}_{3/2}$, $F=3$ blue transition (blue MOT). Continuous loading of the blue MOT is achieved by superimposing the blue laser beam inside a hollow core of infrared (IR) laser beam driving the broad $5{S}_{1/2}$, $F=2\ensuremath{\rightarrow}5{P}_{3/2}$, $F=3$ transition at 780 nm. We typically load $\ensuremath{\sim}{10}^{8}$ atoms in the blue MOT in 2.5 s. We characterize the continuous loading of the blue MOT with various parameters such as magnetic-field gradient, detuning, power and diameter of the blue MOT beam, and diameter of the hollow core (spot) inside the IR MOT beam. We observe that the blue laser beam should overfill the spot of the IR laser beam. This is because the blue laser cools the atoms to a lower temperature even in the presence of the broad IR laser, i.e., in the overlapped region, and hence helps in loading. To support the experimental result, we also present the theoretical framework for cooling atoms in the presence of two lasers driving two different transitions simultaneously. This method of continuous loading of the blue MOT can be useful to produce a continuous atomic beam of cold Rb atoms.

DOI
10.1103/physreva.109.063107

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We report continuous loading of 87Rb^{\text{87}}\mathrm{Rb}87Rb atoms in a magneto-optical trap (MOT) at narrow linewidth, 420-nm 5S1/25{S}_{1/2}5S1/2​, F=2\ensuremath→6P3/2F=2\ensuremath{\rightarrow}6{P}_{3/2}F=2\ensuremath→6P3/2​, F=3F=3F=3 blue transition (blue MOT). Continuous loading of the blue MOT is achieved by superimposing the blue laser beam inside a hollow core of infrared (IR) laser beam driving the broad 5S1/25{S}_{1/2}5S1/2​, F=2\ensuremath→5P3/2F=2\ensuremath{\rightarrow}5{P}_{3/2}F=2\ensuremath→5P3/2​, F=3F=3F=3 transition at 780 nm. We typically load \ensuremath∼108\ensuremath{\sim}{10}^{8}\ensuremath∼108 atoms in the blue MOT in 2.5 s. We characterize the continuous loading of the blue MOT with various parameters such as magnetic-field gradient, detuning, power and diameter of the blue MOT beam, and diameter of the hollow core (spot) inside the IR MOT beam. We observe that the blue laser beam should overfill the spot of the IR laser beam. This is because the blue laser cools the atoms to a lower temperature even in the presence of the broad IR laser, i.e., in the overlapped region, and hence helps in loading. To support the experimental result, we also present the theoretical framework for cooling atoms in the presence of two lasers driving two different transitions simultaneously. This method of continuous loading of the blue MOT can be useful to produce a continuous atomic beam of cold Rb atoms.
Abstract A magneto-optical trap (MOT) at narrow transition offers lower temperature and hence is the key for producing a high phase density atomic cloud and subsequently quantum degeneracy with a large number of atoms for many elements. In this paper, we describe the loading of 87Rb atoms in the MOT using a narrow open transition (5S 1 / 2 → 6P 3 / 2 ) at 420 nm (i.e. blue MOT) from the routinely implemented MOT using a broad cyclic transition (5S 1 / 2 → 5P 3 / 2 ) at 780 nm (i.e. IR MOT). Using the four times narrower transition, we have trapped around 108 atoms in the MOT with a typical temperature of around 54 μ K. We have also studied the behavior of the blue MOT with various parameters such as hold time, detuning, and power of trapping and repumper beams.
We report the observation of significant enhancement in the transfer of laser-cooled 87Rb^{87}\text{R}\text{b}87Rb atoms between two vertically separated magneto-optical traps (MOTs) when an appropriately tuned and aligned hollow laser beam was used. In the experimental setup, the lower MOT was loaded from a continuous flux of atoms ejected from the upper MOT by a resonant push beam. The observed enhancement appears to be mainly due to a slowing down of atoms by the hollow beam after being ejected from the upper MOT.
We present our technique to create a magneto-optical trap (MOT) for dysprosium atoms using the narrow-line cooling transition at 626 nm to achieve suitable conditions for direct loading into an optical dipole trap. The MOT is loaded from an atomic beam via a Zeeman slower using the strongest atomic transition at 421 nm. With this combination of two cooling transitions we can trap up to 2.0·10(8) atoms at temperatures down to 6 μK. This cooling approach is simpler than present work with ultracold dysprosium and provides similar starting conditions for a transfer to an optical dipole trap.
Abstract We report a two-color magneto-optical trap (MOT) for ytterbium atoms where the slowing and trapping functions are separately performed by the singlet transition light ( ) and the triplet transition light ( ), respectively. The two-color MOT is achieved by simultaneously applying laser light on both the broad-linewidth singlet transition and the narrow-linewidth triplet transition. It is highly robust against laser power imbalance even at very low magnetic field gradients, and can operate at magnetic field gradients down to 2 G cm −1 where a conventional MOT using the singlet transition is unable to trap atoms. We load and trap up to atoms directly from an atomic beam at 700 K.
A significant enhancement in the number of cold atoms in an atomic-beam-loaded magneto-optical trap (MOT) for metastable krypton atoms is observed when hollow laser beams are used in a Zeeman slower instead of a Gaussian laser beam. In the Zeeman slower setup, a combination of two hollow laser beams, i.e., a variable-diameter hollow beam generated using a pair of axicon lenses superimposed on a fixed-diameter hollow beam, has been used to reduce the longitudinal velocity of the atoms in the atomic beam below the capture speed of the MOT. The observed enhancement in the number of atoms in the MOT is attributed to reduced destruction of the atom cloud in the MOT and increased cooling of the off-axis atoms in the atomic beam, resulting from the use of hollow beams in the Zeeman slower.