The capture of a moving atom by a non-dissipative trap, such as an optical dipole trap, requires the removal of the excessive kinetic energy of the atom. In this paper, we develop a mechanism to harvest ultra-cold atoms from a guided atom beam into an optical dipole trap by removing their directed kinetic energy. We propose a continuous loading scheme where this is accomplished via deceleration by a magnetic potential barrier followed by optical pumping to the energetically lowest Zeeman sublevel. We theoretically investigate the application of this scheme to the transfer of ultra-cold chromium atoms from a magnetically guided atom beam into a deep optical dipole trap. We discuss the realization of a suitable magnetic field configuration. Based on numerical simulations of the loading process, we analyse the feasibility and efficiency of our loading scheme.The capture of a moving atom by a non-dissipative trap, such as an optical dipole trap, requires the removal of the excessive kinetic energy of the atom. In this paper, we develop a mechanism to harvest ultra-cold atoms from a guided atom beam into an optical dipole trap by removing their directed kinetic energy. We propose a continuous loading scheme where this is accomplished via deceleration by a magnetic potential barrier followed by optical pumping to the energetically lowest Zeeman sublevel. We theoretically investigate the application of this scheme to the transfer of ultra-cold chromium atoms from a magnetically guided atom beam into a deep optical dipole trap. We discuss the realization of a suitable magnetic field configuration. Based on numerical simulations of the loading process, we analyse the feasibility and efficiency of our loading scheme.

arXiv:0912.2244Journal of Physics B Atomic Molecular and Optical PhysicsDec 4, 200914 citations

Dark Optical Traps for Cold Atoms

Nir Friedman, Ariel Kaplan, Nir Davidson

Advances in atomic, molecular, and optical physicsJan 1, 200295 citations

Ultracold collisions of mixed atoms in optical dipole trap loaded from a dark magneto-optical trap

Yanting Zhao, Ting Gong, Zhonghao Li +4 more

Abstract We study the cold collisions of mixed atoms in an optical dipole trap (ODT), which are loaded from a dark magneto-optical trap (MOT). A comprehensive, phenomenological rate equation is presented to derive the ultracold homonuclear and heteronuclear collision rates in loading and holding procedures. Our results show that the cold atoms in the dark MOT can provide a much better stable, initial atomic sample than MOT. The dependence of the heteronuclear collision rate on the trap depth is attributed to the hyperfine-changing collision by the ODT laser with a broad linewidth. The processes of deriving the collision rate are also universal for other kinds of atoms or even molecules.Abstract We study the cold collisions of mixed atoms in an optical dipole trap (ODT), which are loaded from a dark magneto-optical trap (MOT). A comprehensive, phenomenological rate equation is presented to derive the ultracold homonuclear and heteronuclear collision rates in loading and holding procedures. Our results show that the cold atoms in the dark MOT can provide a much better stable, initial atomic sample than MOT. The dependence of the heteronuclear collision rate on the trap depth is attributed to the hyperfine-changing collision by the ODT laser with a broad linewidth. The processes of deriving the collision rate are also universal for other kinds of atoms or even molecules.

Journal of Physics B Atomic Molecular and Optical PhysicsAug 31, 20170 citations

Continuous loading of S01 calcium atoms into an optical dipole trap

Chih-Yun Yang, Purbasha Halder, Oliver Appel +2 more

We demonstrate an efficient scheme for continuous trap loading based upon spatially selective optical pumping. We discuss the case of $^{1}S_{0}$ calcium atoms in an optical dipole trap (ODT), however, similar strategies should be applicable to a wide range of atomic species, which do not permit efficient conventional trap loading. Our starting point is a moderately cold $(\ensuremath{\approx}300\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K})$ and dense $(\ensuremath{\approx}9\ifmmode\times\else\texttimes\fi{}{10}^{9}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3})$ reservoir of metastable $^{3}P_{2}$ atoms in a magneto-optic trap (triplet MOT). A focused $532\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ laser beam produces a strongly elongated optical potential for $^{1}S_{0}$ atoms with up to $350\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K}$ well depth. A weak focused laser beam at $430\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ , carefully superimposed upon the ODT beam, selectively pumps the $^{3}P_{2}$ atoms inside the capture volume to the singlet state, where they are confined by the ODT. The triplet MOT perpetually refills the capture volume with $^{3}P_{2}$ atoms, thus providing a continuous stream of cold atoms into the ODT at a rate of ${10}^{7}\phantom{\rule{0.3em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$. Limited by evaporation loss, in $200\phantom{\rule{0.3em}{0ex}}\mathrm{ms}$ we typically load $5\ifmmode\times\else\texttimes\fi{}{10}^{5}$ atoms with $3.5\ifmmode\times\else\texttimes\fi{}{10}^{10}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$ peak density and axial and radial temperatures of 300 and $85\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K}$, respectively. After terminating the loading we observe evaporation during $50\phantom{\rule{0.3em}{0ex}}\mathrm{ms}$ , typically leaving us with ${10}^{5}$ atoms with nearly equal radial and axial temperatures close to $40\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K}$ and a peak density of $5\ifmmode\times\else\texttimes\fi{}{10}^{11}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$. A simple model is presented, which identifies the relevant physical mechanisms of the loading and decay dynamics. We point out that a comparable scheme could be employed to load a dipole trap with $^{3}P_{0}$ atoms.We demonstrate an efficient scheme for continuous trap loading based upon spatially selective optical pumping. We discuss the case of $^{1}S_{0}$ calcium atoms in an optical dipole trap (ODT), however, similar strategies should be applicable to a wide range of atomic species, which do not permit efficient conventional trap loading. Our starting point is a moderately cold $(\ensuremath{\approx}300\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K})$ and dense $(\ensuremath{\approx}9\ifmmode\times\else\texttimes\fi{}{10}^{9}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3})$ reservoir of metastable $^{3}P_{2}$ atoms in a magneto-optic trap (triplet MOT). A focused $532\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ laser beam produces a strongly elongated optical potential for $^{1}S_{0}$ atoms with up to $350\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K}$ well depth. A weak focused laser beam at $430\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$, carefully superimposed upon the ODT beam, selectively pumps the $^{3}P_{2}$ atoms inside the capture volume to the singlet state, where they are confined by the ODT. The triplet MOT perpetually refills the capture volume with $^{3}P_{2}$ atoms, thus providing a continuous stream of cold atoms into the ODT at a rate of ${10}^{7}\phantom{\rule{0.3em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$. Limited by evaporation loss, in $200\phantom{\rule{0.3em}{0ex}}\mathrm{ms}$ we typically load $5\ifmmode\times\else\texttimes\fi{}{10}^{5}$ atoms with $3.5\ifmmode\times\else\texttimes\fi{}{10}^{10}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$ peak density and axial and radial temperatures of 300 and $85\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K}$, respectively. After terminating the loading we observe evaporation during $50\phantom{\rule{0.3em}{0ex}}\mathrm{ms}$, typically leaving us with ${10}^{5}$ atoms with nearly equal radial and axial temperatures close to $40\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K}$ and a peak density of $5\ifmmode\times\else\texttimes\fi{}{10}^{11}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$. A simple model is presented, which identifies the relevant physical mechanisms of the loading and decay dynamics. We point out that a comparable scheme could be employed to load a dipole trap with $^{3}P_{0}$ atoms.

arXiv:0706.0796Physical Review ASep 28, 200720 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

We demonstrate an efficient scheme for continuous trap loading based upon spatially selective optical pumping. We discuss the case of

^{1}S_{0}

calcium atoms in an optical dipole trap (ODT), however, similar strategies should be applicable to a wide range of atomic species, which do not permit efficient conventional trap loading. Our starting point is a moderately cold $(\ensuremath{\approx}300\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K})$ and dense $(\ensuremath{\approx}9\ifmmode\times\else\texttimes\fi{}{10}^{9}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3})$ reservoir of metastable

^{3}P_{2}

atoms in a magneto-optic trap (triplet MOT). A focused

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

laser beam produces a strongly elongated optical potential for

^{1}S_{0}

atoms with up to $350\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K}$ well depth. A weak focused laser beam at

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

, carefully superimposed upon the ODT beam, selectively pumps the

^{3}P_{2}

atoms inside the capture volume to the singlet state, where they are confined by the ODT. The triplet MOT perpetually refills the capture volume with

^{3}P_{2}

atoms, thus providing a continuous stream of cold atoms into the ODT at a rate of ${10}^{7}\phantom{\rule{0.3em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$. Limited by evaporation loss, in

200\phantom{\rule{0.3em}{0ex}}\mathrm{ms}

we typically load $5\ifmmode\times\else\texttimes\fi{}{10}^{5}$ atoms with $3.5\ifmmode\times\else\texttimes\fi{}{10}^{10}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$ peak density and axial and radial temperatures of 300 and $85\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K}$, respectively. After terminating the loading we observe evaporation during

50\phantom{\rule{0.3em}{0ex}}\mathrm{ms}

, typically leaving us with

{10}^{5}

atoms with nearly equal radial and axial temperatures close to $40\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K}$ and a peak density of $5\ifmmode\times\else\texttimes\fi{}{10}^{11}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$. A simple model is presented, which identifies the relevant physical mechanisms of the loading and decay dynamics. We point out that a comparable scheme could be employed to load a dipole trap with

^{3}P_{0}

atoms.