Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:2003.05799 · Physica Scripta

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

Kavish Bhardwaj, Surjya Prakash Ram, S Singh, Vibhuti Bhushan Tiwari, Satya Ram Mishra

Published Oct 29, 2020• 2 citations
arXivHTMLPDF

Abstract

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.

DOI
10.1088/1402-4896/abc5f1

Related papers

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.

arXiv:0807.3672•Physical Review A•Sep 25, 2008•37 citations

Calculation of AC Stark shift of 5S_(1/2) and 5P_(3/2) states of Rb atoms in optical dipole trap

Junmin Wang

Based on the two-level and multi-level models,the AC Stark shift of the 5S1/2 and 5P3/2 states of 87Rb atoms in an Optical Dipole Trap(ODT) formed by a strongly-focused single Gaussian laser beam is analyzed and calculated.For performance of molasses cooling of 87Rb atoms in the Far-off-resonance Trap(FORT) by 852 nm Gaussian laser beam,the AC Stark shift of 5S1/2F=2-5P3/2F′=3 cycling transition for cooling is also calculated,results show that the frequency shift has an important impact on the molasses cooling process.Furthermore,the AC Stark shift of 87Rb 5S1/2|F=2,mF=±2〉 and 5P3/2|F′=3,mF=±3〉 states versus the wavelength of the ODT laser is analyzed,which shows that there is no magic wavelength for 5S1/2-5P3/2 transition of 87Rb atoms in the red-off-resonance condition.

Chinese Journal of Optics and Applied Optics•Jan 1, 2010•1 citation

Evaporative Cooling of Atoms to Quantum Degeneracy in an Optical Dipole Trap

Saptarishi Chaudhuri, Sanjukta Roy, C. S. Unnikrishnan

We discuss our experimental results on forced evaporative cooling of cold rubidium 87 Rb atoms to quantum degeneracy in an Optical Dipole Trap. The atoms are first trapped and cooled in a magneto-optical trap (MOT) loaded from a continuous beam of cold atoms [1]. More than 10 10 atoms are trapped in the MOT and then about 10 8 atoms are transferred to a Quasi-Electrostatic Trap (QUEST) formed by tightly focused CO2 laser (λ = 10.6μ m ) beams intersecting at their foci in an orthogonal configuration in the horizontal plane. Before loading the atoms into the dipole trap, the phase-space density of the atomic ensemble was increased making use of sub-doppler cooling at large detuning and the temporal dark MOT technique. In a MOT the phase-space density of the atomic ensemble is six orders of magnitude less than what is required to achieve quantum degeneracy. After transferring atoms into the dipole trap efficiently, phase-space density increases by a factor of 10 3 . Further increase in phase-space density to quantum degeneracy is achieved by forced evaporative cooling of atoms in the dipole trap. The evaporative cooling process involves a gradual reduction of the trap depth by ramping down the trapping laser intensity over a second. The temperature of the cold atomic cloud was measured by time-of-flight (TOF) technique. The spatial distribution of the atoms is measured using absorption imaging. We report results of evaporative cooling in a single beam and in a crossed double-beam dipole traps. Due to the large initial phase space density, and large initial number of atoms trapped, the quantum phase transition occurs after about 600 ms of evaporative cooling in our optimized crossed dipole trap.

Journal of Physics Conference Series•Sep 1, 2007•12 citations

ac-Stark shift and photoionization of Rydberg atoms in an optical dipole trap

Frank Markert, P Würtz, Andreas Koglbauer +3 more

We have measured the ac-Stark shift of the 14 D 5/2 Rydberg state of rubidium 87 in an optical dipole trap formed by a focused CO 2 laser. We found good quantitative agreement of the result with the model of a free electron experiencing a ponderomotive potential in the light field. In order to reproduce the observed spectra, we take into account the broadening of the Rydberg state due to photoionization. The extracted cross section is compatible with previous measurements on neighboring Rydberg states.

arXiv:1011.0837•New Journal of Physics•Nov 2, 2010•12 citations

Studies on cold atoms trapped in a Quasi-Electrostatic optical dipole trap

Sanjukta Roy, Saptarishi Chaudhuri, C. S. Unnikrishnan

We discuss the results of measurements of the temperature and density distribution of cold Rubidium atoms trapped and cooled in an optical dipole trap formed by focussed CO 2 laser beams at a wavelength of 10.6 μ m from a cold, collimated and intense atomic beam of flux 2 × 10 10 atoms/s produced using an elongated 2D + MOT. A large number of rubidium atoms (⩾ 10 10 ) were trapped in the MOT and the number density of atoms were further increased by making a temporal dark MOT to prevent density-limiting processes like photon rescattering by atoms at the trap centre. Subsequently, between 10 7 to 10 8 cold atoms at a temperature below 30 μK were transferred into a Quasi-Electrostatic trap (QUEST) formed by focussed CO 2 laser beams at the MOT centre. Both single beam and crossed dual beam dipole traps were studied with a total output power of 50 W from the CO 2 laser with focal spot sizes less than 100 microns. Various measurements were done on the cold atoms trapped in the dipole trap. The total atom number in the dipole trap and the spatial atom number density distribution in the trap was measured by absorption imaging technique. The temperature was determined from time-of-flight (TOF) data as well as from the absorption images after ballistic expansion of the atom cloud released from the dipole trap. The results from measurements are used to maximize the initial phase-space density prior to forced evaporative cooling to produce a Bose-Einstein Condensate.

Journal of Physics Conference Series•Sep 1, 2007•2 citations

Magic-wavelength optical dipole trap of cesium and rubidium atoms

Junmin Wang, Yongjie Cheng, Shanlong Guo +2 more

Optical dipole traps (ODT) with far-off-resonance laser are important tools in more and more present cold-atom experiments, which allow confinement of laser-cooled atoms with a long storage time. Particularly, the magic wavelength ODT can cancel the position-dependent spatially inhomogeneous light shift of desired atomic transition, which is introduced by the ODT laser beam. Now it plays an important role in the state-insensitive quantum engineering and the atomic optical clock. To verify the magic wavelength or the magic wavelength combination for D2 line transition of cesium (Cs) and rubidium (Rb) atoms, we calculated and analyzed the light shift of the 133Cs 6S1/2 - 6P3/2 transition for a monochromatic ODT, and also the 87Rb 5S1/2 - 5P3/2 transition for a dichromatic ODT with a laser frequency ratio of 2:1. Also a dichromatic magic-wavelength ODT laser system for 87Rb atoms is proposed and experimentally realized by employing the quasi-phase-matched frequency doubling technique with telecom laser and fiber amplifier.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Apr 11, 2012•2 citations
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.
We report on light-shift tomography of a cloud of 87Rb^{87}\mathrm{Rb}87Rb atoms in a far-detuned optical-dipole trap at 1565nm1565\phantom{\rule{0.3em}{0ex}}\mathrm{nm}1565nm. 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.
Based on the two-level and multi-level models,the AC Stark shift of the 5S1/2 and 5P3/2 states of 87Rb atoms in an Optical Dipole Trap(ODT) formed by a strongly-focused single Gaussian laser beam is analyzed and calculated.For performance of molasses cooling of 87Rb atoms in the Far-off-resonance Trap(FORT) by 852 nm Gaussian laser beam,the AC Stark shift of 5S1/2F=2-5P3/2F′=3 cycling transition for cooling is also calculated,results show that the frequency shift has an important impact on the molasses cooling process.Furthermore,the AC Stark shift of 87Rb 5S1/2|F=2,mF=±2〉 and 5P3/2|F′=3,mF=±3〉 states versus the wavelength of the ODT laser is analyzed,which shows that there is no magic wavelength for 5S1/2-5P3/2 transition of 87Rb atoms in the red-off-resonance condition.
We discuss our experimental results on forced evaporative cooling of cold rubidium 87 Rb atoms to quantum degeneracy in an Optical Dipole Trap. The atoms are first trapped and cooled in a magneto-optical trap (MOT) loaded from a continuous beam of cold atoms [1]. More than 10 10 atoms are trapped in the MOT and then about 10 8 atoms are transferred to a Quasi-Electrostatic Trap (QUEST) formed by tightly focused CO2 laser (λ = 10.6μ m ) beams intersecting at their foci in an orthogonal configuration in the horizontal plane. Before loading the atoms into the dipole trap, the phase-space density of the atomic ensemble was increased making use of sub-doppler cooling at large detuning and the temporal dark MOT technique. In a MOT the phase-space density of the atomic ensemble is six orders of magnitude less than what is required to achieve quantum degeneracy. After transferring atoms into the dipole trap efficiently, phase-space density increases by a factor of 10 3 . Further increase in phase-space density to quantum degeneracy is achieved by forced evaporative cooling of atoms in the dipole trap. The evaporative cooling process involves a gradual reduction of the trap depth by ramping down the trapping laser intensity over a second. The temperature of the cold atomic cloud was measured by time-of-flight (TOF) technique. The spatial distribution of the atoms is measured using absorption imaging. We report results of evaporative cooling in a single beam and in a crossed double-beam dipole traps. Due to the large initial phase space density, and large initial number of atoms trapped, the quantum phase transition occurs after about 600 ms of evaporative cooling in our optimized crossed dipole trap.
We have measured the ac-Stark shift of the 14 D 5/2 Rydberg state of rubidium 87 in an optical dipole trap formed by a focused CO 2 laser. We found good quantitative agreement of the result with the model of a free electron experiencing a ponderomotive potential in the light field. In order to reproduce the observed spectra, we take into account the broadening of the Rydberg state due to photoionization. The extracted cross section is compatible with previous measurements on neighboring Rydberg states.
We discuss the results of measurements of the temperature and density distribution of cold Rubidium atoms trapped and cooled in an optical dipole trap formed by focussed CO 2 laser beams at a wavelength of 10.6 μ m from a cold, collimated and intense atomic beam of flux 2 × 10 10 atoms/s produced using an elongated 2D + MOT. A large number of rubidium atoms (⩾ 10 10 ) were trapped in the MOT and the number density of atoms were further increased by making a temporal dark MOT to prevent density-limiting processes like photon rescattering by atoms at the trap centre. Subsequently, between 10 7 to 10 8 cold atoms at a temperature below 30 μK were transferred into a Quasi-Electrostatic trap (QUEST) formed by focussed CO 2 laser beams at the MOT centre. Both single beam and crossed dual beam dipole traps were studied with a total output power of 50 W from the CO 2 laser with focal spot sizes less than 100 microns. Various measurements were done on the cold atoms trapped in the dipole trap. The total atom number in the dipole trap and the spatial atom number density distribution in the trap was measured by absorption imaging technique. The temperature was determined from time-of-flight (TOF) data as well as from the absorption images after ballistic expansion of the atom cloud released from the dipole trap. The results from measurements are used to maximize the initial phase-space density prior to forced evaporative cooling to produce a Bose-Einstein Condensate.
Optical dipole traps (ODT) with far-off-resonance laser are important tools in more and more present cold-atom experiments, which allow confinement of laser-cooled atoms with a long storage time. Particularly, the magic wavelength ODT can cancel the position-dependent spatially inhomogeneous light shift of desired atomic transition, which is introduced by the ODT laser beam. Now it plays an important role in the state-insensitive quantum engineering and the atomic optical clock. To verify the magic wavelength or the magic wavelength combination for D2 line transition of cesium (Cs) and rubidium (Rb) atoms, we calculated and analyzed the light shift of the 133Cs 6S1/2 - 6P3/2 transition for a monochromatic ODT, and also the 87Rb 5S1/2 - 5P3/2 transition for a dichromatic ODT with a laser frequency ratio of 2:1. Also a dichromatic magic-wavelength ODT laser system for 87Rb atoms is proposed and experimentally realized by employing the quasi-phase-matched frequency doubling technique with telecom laser and fiber amplifier.