Experimental Investigation of the Influence of the Laser Beam Waist on Cold Atom Guiding Efficiency.

Ningfang Song,Xiaobin Xu,Di Hu,Wei Li,Xiangxiang Lu,Yitong Song

doi:10.3390/s18030717

Abstract

The primary purpose of this study is to investigate the influence of the vertical guiding laser beam waist on cold atom guiding efficiency. In this study, a double magneto-optical trap (MOT) apparatus is used. With an unbalanced force in the horizontal direction, a cold atomic beam is generated by the first MOT. The cold atoms enter the second chamber and are then re-trapped and cooled by the second MOT. By releasing a second atom cloud, the process of transferring the cold atoms from MOT to the dipole trap, which is formed by a red-detuned converged 1064-nm laser, is experimentally demonstrated. And after releasing for 20 ms, the atom cloud is guided to a distance of approximately 3 mm. As indicated by the results, the guiding efficiency depends strongly on the laser beam waist; the efficiency reaches a maximum when the waist radius (w0) of the laser is in the range of 15 to 25 μm, while the initial atom cloud has a radius of 133 μm. Additionally, the properties of the atoms inside the dipole potential trap, such as the distribution profile and lifetime, are deduced from the fluorescence images.

Highlights

Over the past several years, there has been a growing interest in the transferring and guiding of atoms by the dipole potential trap
In this study, using a red-detuned Gaussian laser, we experimentally demonstrated the existence of an optimal laser beam waist for the guiding efficiency of cold atoms
Our experimental results demonstrate that, in the case that cold atoms are released from the magneto-optical trap (MOT) and expanding ballistically in the red-detuned guiding potential trap, the guiding efficiency strongly depends on the beam waist of the laser

Summary

Introduction

Over the past several years, there has been a growing interest in the transferring and guiding of atoms by the dipole potential trap. The concept of guiding cooled atoms by a red-detuned laser beam was theoretically proposed in 1978 [6]. By combining the magneto-optical trap (MOT) with a far-off resonance potential trap, an atomic fountain was guided by a far-off resonance laser in 1999 [8]. The following studies were conducted to investigate the relative parameters to improve the efficiency of initially transferred atoms in the optical dipole potential, such as the intensity and detuning of the laser beam [10,11]. The influence of the guiding laser beam waist on the guiding efficiency of cold atoms was not investigated thoroughly through experiments but rather through theoretical calculations. Using a focused red-detuned Gaussian laser beam, Pruvost et al [12]

Objectives

Results

Conclusion