Ramsey Imaging of Optical Dipole Traps

The mapping of the potential landscape with high spatial resolution is crucial for quantum technologies based on ultracold atoms. However, the imaging of optical dipole traps is challenging because purely optical methods, commonly used to profile laser beams in free space, are not applicable in a vacuum. In this work, we demonstrate precise in situ imaging of optical dipole traps by probing a hyperfine transition with Ramsey interferometry. Thereby, we obtain an absolute map of the potential landscape with micrometer resolution and shot-noise-limited spectral precision. The idea of the technique is to control the polarization ellipticity of the trap laser beam to induce a differential light shift proportional to the trap potential. By studying the response to polarization ellipticity, we uncover a small but significant nonlinearity in addition to a dominant linear behavior, which is explained by the geometric distribution of the atomic ensemble. Our technique for imaging of optical traps can find wide application in quantum technologies based on ultracold atoms, as it applies to multiple atomic species and is not limited to a particular wavelength or trap geometry.The mapping of the potential landscape with high spatial resolution is crucial for quantum technologies based on ultracold atoms. However, the imaging of optical dipole traps is challenging because purely optical methods, commonly used to profile laser beams in free space, are not applicable in a vacuum. In this work, we demonstrate precise in situ imaging of optical dipole traps by probing a hyperfine transition with Ramsey interferometry. Thereby, we obtain an absolute map of the potential landscape with micrometer resolution and shot-noise-limited spectral precision. The idea of the technique is to control the polarization ellipticity of the trap laser beam to induce a differential light shift proportional to the trap potential. By studying the response to polarization ellipticity, we uncover a small but significant nonlinearity in addition to a dominant linear behavior, which is explained by the geometric distribution of the atomic ensemble. Our technique for imaging of optical traps can find wide application in quantum technologies based on ultracold atoms, as it applies to multiple atomic species and is not limited to a particular wavelength or trap geometry.

arXiv:2106.05871Physical Review AppliedAug 24, 202110 citations

Characterizing single atom optical dipole traps

Chung-Yu Shih, Michael J. Gibbons, Michael Chapman

Bulletin of the American Physical SocietyJun 7, 20122 citations

Absorption imaging of trapped atoms in presence of AC-Stark shift

Kavish Bhardwaj, Surjya Prakash Ram, S Singh +2 more

Abstract In this work, the effect of AC-Stark shift of atomic energy levels in an optical dipole trap (ODT) on in situ absorption imaging of the trapped atoms has been investigated. The Stark shift of various energy levels of 87 Rb atoms relevant for trapping in the optical dipole trap (ODT) has been calculated. The spatially varying AC-Stark shift of energy levels due to ODT beam results in position dependent absorption cross-section of the atom at the absorption probe laser wavelength, which significantly modifies the measured optical density (OD) of the trapped atom cloud during the in situ absorption imaging. We have estimated the number of atoms trapped in the ODT taking AC-Stark shift into account. The estimated numbers are found to be higher at higher ODT beam power, making a qualitative agreement with larger trap depth at higher ODT beam power. This work can be particularly useful in estimating the in situ loss rate of atoms from the trap during the evaporative cooling of the trapped atom cloud.Abstract In this work, the effect of AC-Stark shift of atomic energy levels in an optical dipole trap (ODT) on in situ absorption imaging of the trapped atoms has been investigated. The Stark shift of various energy levels of 87 Rb atoms relevant for trapping in the optical dipole trap (ODT) has been calculated. The spatially varying AC-Stark shift of energy levels due to ODT beam results in position dependent absorption cross-section of the atom at the absorption probe laser wavelength, which significantly modifies the measured optical density (OD) of the trapped atom cloud during the in situ absorption imaging. We have estimated the number of atoms trapped in the ODT taking AC-Stark shift into account. The estimated numbers are found to be higher at higher ODT beam power, making a qualitative agreement with larger trap depth at higher ODT beam power. This work can be particularly useful in estimating the in situ loss rate of atoms from the trap during the evaporative cooling of the trapped atom cloud.

arXiv:2003.05799Physica ScriptaOct 29, 20202 citations

Optical Dipole Traps for Neutral Atoms

Rudolf Grimm, Matthias Weidemüller, Yuri B. Ovchinnikov

Advances in atomic, molecular, and optical physicsJan 1, 20001,549 citations

Optical Dipole Trap

Galina A. Nemova

SPIE eBooksNov 6, 20190 citations

Light-shift tomography in an optical-dipole trap for neutral atoms

Jean-Philippe Brantut, Jean‐François Clément, Martin Robert-De-Saint-Vincent +5 more

We report on light-shift tomography of a cloud of $^{87}\mathrm{Rb}$ atoms in a far-detuned optical-dipole trap at $1565\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ . Our method is based on standard absorption imaging, but takes advantage of the strong light shift of the excited state of the imaging transition, which is due to a quasiresonance of the trapping laser with a higher excited level. We use this method to (i) map the equipotentials of a crossed optical-dipole trap and (ii) study the thermalization of an atomic cloud by following the evolution of the potential energy of atoms during the free-evaporation process.We report on light-shift tomography of a cloud of $^{87}\mathrm{Rb}$ atoms in a far-detuned optical-dipole trap at $1565\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$. Our method is based on standard absorption imaging, but takes advantage of the strong light shift of the excited state of the imaging transition, which is due to a quasiresonance of the trapping laser with a higher excited level. We use this method to (i) map the equipotentials of a crossed optical-dipole trap and (ii) study the thermalization of an atomic cloud by following the evolution of the potential energy of atoms during the free-evaporation process.

arXiv:0807.3672Physical Review ASep 25, 200837 citations

We report on light-shift tomography of a cloud of

^{87}\mathrm{Rb}

atoms in a far-detuned optical-dipole trap at

1565\phantom{\rule{0.3em}{0ex}}\mathrm{nm}

. Our method is based on standard absorption imaging, but takes advantage of the strong light shift of the excited state of the imaging transition, which is due to a quasiresonance of the trapping laser with a higher excited level. We use this method to (i) map the equipotentials of a crossed optical-dipole trap and (ii) study the thermalization of an atomic cloud by following the evolution of the potential energy of atoms during the free-evaporation process.