We propose a laser-driven Sisyphus-cooling scheme for atoms confined in a far-off resonance optical dipole trap. Utilizing the differential trap-induced ac Stark shift, two electronic levels of the atom are resonantly coupled by a cooling laser preferentially near the trap bottom. After absorption of a cooling photon, the atom loses energy by climbing the steeper potential, and then spontaneously decays preferentially away from the trap bottom. The proposed method is particularly suited to cooling alkaline-earth-metal-like atoms where two-level systems with narrow electronic transitions are present. Numerical simulations for the cases of ${}^{88}$ Sr and ${}^{174}$ Yb demonstrate the expected recoil and Doppler temperature limits. The method requires a relatively small number of scattered photons and can potentially lead to phase-space densities approaching quantum degeneracy in subsecond time scales.We propose a laser-driven Sisyphus-cooling scheme for atoms confined in a far-off resonance optical dipole trap. Utilizing the differential trap-induced ac Stark shift, two electronic levels of the atom are resonantly coupled by a cooling laser preferentially near the trap bottom. After absorption of a cooling photon, the atom loses energy by climbing the steeper potential, and then spontaneously decays preferentially away from the trap bottom. The proposed method is particularly suited to cooling alkaline-earth-metal-like atoms where two-level systems with narrow electronic transitions are present. Numerical simulations for the cases of ${}^{88}$Sr and ${}^{174}$Yb demonstrate the expected recoil and Doppler temperature limits. The method requires a relatively small number of scattered photons and can potentially lead to phase-space densities approaching quantum degeneracy in subsecond time scales.

arXiv:1110.3439Physical Review ADec 20, 201120 citations

rf-induced Sisyphus cooling in an optical dipole trap

Kurt W. Miller, Stephan Dürr, Carl Wieman

A cooling process for optical dipole traps, rf-induced Sisyphus cooling in a circularly polarized far-off-resonance trap, is demonstrated. Cooling rates of up to $\ensuremath{\approx}300 \ensuremath{\mu}\mathrm{K}/\mathrm{s}$ are observed without significant atom loss. The final temperature achieved was (a somewhat disappointing) $17 \ensuremath{\mu}\mathrm{K}.$ Experimental studies and theoretical analysis of this cooling process were carried out, which explain that the temperature limit is due to an equilibrium between the small fraction of total thermal energy that is removed per Sisyphus cycle and the multiple photon recoils that are required to complete each cycle. Light-induced collisional loss made it difficult to operate under conditions where a larger fraction of the energy would be removed. A method for storing atoms in an optical trap with only a single confined spin state is also demonstrated.A cooling process for optical dipole traps, rf-induced Sisyphus cooling in a circularly polarized far-off-resonance trap, is demonstrated. Cooling rates of up to $\ensuremath{\approx}300 \ensuremath{\mu}\mathrm{K}/\mathrm{s}$ are observed without significant atom loss. The final temperature achieved was (a somewhat disappointing) $17 \ensuremath{\mu}\mathrm{K}.$ Experimental studies and theoretical analysis of this cooling process were carried out, which explain that the temperature limit is due to an equilibrium between the small fraction of total thermal energy that is removed per Sisyphus cycle and the multiple photon recoils that are required to complete each cycle. Light-induced collisional loss made it difficult to operate under conditions where a larger fraction of the energy would be removed. A method for storing atoms in an optical trap with only a single confined spin state is also demonstrated.

Physical Review AAug 19, 200225 citations

Feasibility of narrow-line cooling in optical dipole traps

Ch. Grain, Tatiana Nazarova, C. Degenhardt +5 more

The European Physical Journal DMar 8, 200710 citations

Efficient intensity-gradient cooling of atoms in a weak standing-wave hollow-beam trap

Zhengling Wang, Jianping Yin

We propose a trap scheme for cold alkali-metal atoms with an efficient intensity-gradient induced Sisyphus cooling in a weak standing-wave hollow-beam gravito-optical trap, which is composed of the interference of two well collimated, counterpropagating doughnut hollow beams with an intensity difference and a plug beam. We calculate the intensity distribution of the weak standing-wave hollow-beam field and its intensity gradient one, and find that such an optical dipole trap with an extremely high intensity gradient is desirable to realize an efficient intensity-gradient cooling for alkali-metal atoms in the trap. We also calculate the optical potentials, instantaneous dipole forces and spontaneous emission rates for a three-level dressed atom and study the dynamic process of intensity-gradient cooling of $^{87}\mathrm{Rb}$ atoms in the weak standing-wave hollow-beam trap by Monte Carlo simulations. Our study shows that the minimum optical potential at each node in our dipole trap is high enough to trap almost all cold atoms with a temperature of $120\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K}$ released from a standard magneto-optical trap, and an ultracold $^{87}\mathrm{Rb}$ atomic sample with a temperature of $\ensuremath{\sim}0.73\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K}$ can be obtained in the trap. Starting from this stage, an all-optical Bose-Einstein condensation (BEC) could be realized by using the optical-potential evaporative cooling.We propose a trap scheme for cold alkali-metal atoms with an efficient intensity-gradient induced Sisyphus cooling in a weak standing-wave hollow-beam gravito-optical trap, which is composed of the interference of two well collimated, counterpropagating doughnut hollow beams with an intensity difference and a plug beam. We calculate the intensity distribution of the weak standing-wave hollow-beam field and its intensity gradient one, and find that such an optical dipole trap with an extremely high intensity gradient is desirable to realize an efficient intensity-gradient cooling for alkali-metal atoms in the trap. We also calculate the optical potentials, instantaneous dipole forces and spontaneous emission rates for a three-level dressed atom and study the dynamic process of intensity-gradient cooling of $^{87}\mathrm{Rb}$ atoms in the weak standing-wave hollow-beam trap by Monte Carlo simulations. Our study shows that the minimum optical potential at each node in our dipole trap is high enough to trap almost all cold atoms with a temperature of $120\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K}$ released from a standard magneto-optical trap, and an ultracold $^{87}\mathrm{Rb}$ atomic sample with a temperature of $\ensuremath{\sim}0.73\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K}$ can be obtained in the trap. Starting from this stage, an all-optical Bose-Einstein condensation (BEC) could be realized by using the optical-potential evaporative cooling.

Physical Review AJul 21, 200610 citations

Sisyphus cooling of Trapped Ions as a Route to Experiments in the Quantum Regime

P. C. Haljan, Sara Ejtemaee

Bulletin of the American Physical SocietyMay 27, 20160 citations

{}^{88}

Sr and

{}^{174}

Yb demonstrate the expected recoil and Doppler temperature limits. The method requires a relatively small number of scattered photons and can potentially lead to phase-space densities approaching quantum degeneracy in subsecond time scales.

^{87}\mathrm{Rb}

atoms in the weak standing-wave hollow-beam trap by Monte Carlo simulations. Our study shows that the minimum optical potential at each node in our dipole trap is high enough to trap almost all cold atoms with a temperature of $120\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K}$ released from a standard magneto-optical trap, and an ultracold

^{87}\mathrm{Rb}

atomic sample with a temperature of $\ensuremath{\sim}0.73\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K}$ can be obtained in the trap. Starting from this stage, an all-optical Bose-Einstein condensation (BEC) could be realized by using the optical-potential evaporative cooling.