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Quantum-Atom Optics Downunder (QAO)

Molecular BEC in a Low Power Crossed Dipole Trap

Jean-Noël Fuchs, G. Veeravalli, Paul Dyke, E. D. Kuhnle, G J Duffy, Chris J. Vale, Peter Hannaford, W J Rowlands

Published Jan 1, 2007• 0 citations
Publisher

Abstract

We create Bose-Einstein condensates of6Li2molecules in an all-optical setup using a low power (25 W) crossed dipole trap. Our system contains a number of simplifications compared to existing setups and offers a high degree of flexibility in the trapping geometry. We will present our latest results and report on progress towards making p-wave Feshbach molecules.

DOI
10.1364/qao.2007.qthb2

Related papers

Molecular Bose–Einstein condensation in a versatile low power crossed dipole trap

Jean-Noël Fuchs, G J Duffy, G. Veeravalli +5 more

We produce Bose–Einstein condensates of 6 Li 2 molecules in a low power (22 W) crossed optical dipole trap. Fermionic 6 Li atoms are collected in a magneto-optical trap from a Zeeman slowed atomic beam and then loaded into the optical dipole trap where they are evaporatively cooled to quantum degeneracy. Our simplified system offers a high degree of flexibility in trapping geometry for studying ultracold Fermi and Bose gases.

arXiv:0709.2212•Journal of Physics B Atomic Molecular and Optical Physics•Oct 9, 2007•25 citations

Molecular Bose-Einstein condensates and p-wave Feshbach molecules of 6Li2

Fuchs, Jurgen

This thesis describes the production of molecular Bose-Einstein condensates (BEC) of 6Li2 dimers and binding energy measurements of p-wave Feshbach molecules. A σ− Zeeman slower is used to produce a continuous beam of isotopically enriched 6Li atoms at speeds low enough to load a magneto-optical trap (MOT). We currently have a flux of slowed atoms of ~ 5 · 106 atoms/s loading the MOT with more than 108 atoms. We then transfer up to 106 atoms in an almost equal spin mixture of the two lowest hyperfine states into an optical dipole trap. We achieved condensates in three different crossed optical dipole trap geometries. The initial low power optical dipole trap was formed using light from a 25WVersaDisk Yb:YAG laser at 1030 nm. It consisted of a 15 W beam crossed with a 13 W beam at about 80 degrees with a waist of approximately 30 μm in each beam. By translating the focus of the second beam we could change the trap geometry from near symmetric to elongated. Nowadays, we produce condensates in a crossed dipole trap formed by a 100 W fibre laser. Both arms are focussed to a waist of 40 μm, cross each other at 14 degrees and have laser powers of ~80 W and ~70 W, respectively. Evaporative cooling is achieved by reducing the laser power near the broad s-wave Feshbach resonance at 834 G. By tuning to the low magnetic field side (770 G) of the Feshbach resonance molecules are formed through three-body recombination at sufficiently low temperatures. Further evaporation leads to the creation of a molecular BEC. After reducing the laser power by a factor of about 1000 in approximately 3 s we have observed more than 30 000 condensed molecules. During the evaporation the temperature decreases from about 100 μK to below 100 nK. We present measurements of the binding energies of 6Li p-wave Feshbach molecules formed in combinations of the |F = 1/2,mF = +1/2i (|1i) and |F = 1/2,mF = −1/2i (|2i) states. The binding energies scale linearly with magnetic field detuning for all three resonances. The relative molecular magnetic moments are found to be 113 ± 7 μK/G, 111 ± 6 μK/G and 118 ± 8 μK/G for the |1i − |1i, |1i − |2i and |2i − |2i resonances, respectively, in good agreement with theoretical predictions.

•Jan 1, 2009•0 citations

Cold Atoms and Bose-Einstein Condensates in Optical Dipole Potentials

J. Nes

In 1925, Einstein predicted the condensation of bosons into the ground state of the system for low (but finite) temperatures. Several phenomena, including superfluidity and superconductivity have been associated with Bose-Einstein condensation, but these systems interact strongly with their environment and pure Bose-Einstein condensation could not be established. It took 70 years, in which time the laser was discovered, and laser cooling techniques to manipulate atoms in a dilute atomic gas, before Bose-Einstein condensation in dilute atomic gases could be demonstrated in 1995. In the first condensation experiments, BECs were created in a magnetic trap. Since in a magnetic trap not all mF states of the atom can be trapped simultaneously, thereby limiting the number of experiments that can be done, other ways of trapping and generating BECs were sought and found. In 2001, the first all-optical BEC was made, where the dipole force was used to trap atoms in the crossing of two far red detuned laser beams. In an optical dipole trap not only atoms in different internal states can be trapped, but also different atomic species simultaneously. In this thesis, the formation of an all-optical Bose-Einstein condensate with rubidium atoms is presented. Conventional all-optical BECs are usually created in high power CO2 laser dipole traps, or have complicated laser cooling schemes and complex dipole trap setups. In our simple and straightforward setup, we load rubidium atoms from a magneto-optical trap into a crossed optical dipole trap created by a single frequency Yb:YAG laser with a wavelength at 1030 nm. The small wavelength allows for a small diffraction limit, and permits us to use standard optical materials, thus making the experimental setup cost effective. Other attempts to achieve Bose-Einstein condensation in a multi-mode (frequency) fiber laser at 1064 nm failed, because the atom loss was quite high. It is assumed that the multi-mode character of the fiber laser induces Raman transitions in rubidium atoms, thereby heating them. We can trap about ∼ 5E7 atoms in a single beam dipole trap out of ∼ 5E9 atoms trapped in theMOT, and ∼ 350,000 atoms can be trapped in a crossed beam dipole trap due to the smaller trap volume. 70% of the atoms in the dipole trap is optically pumped into one mF state. Quantum degeneracy is reached by evaporatively cooling the atoms in the crossed dipole trap by ramping down the laser power with three linear ramps. We can independently change the power of each beam by an AOM. This allows us to use one beam as an atom waveguide for future experiments. After evaporation, we typically have about 10,000 atoms at a temperature below the critical temperature. We have proved Bose-Einstein condensation by using the anisotropic expansion of a quantum degenerate gas trapped in an anisotropic potential. The aspect ratio of our atom cloud changed during a time of flight from 0.7 to 1.2 in 10 ms, thus proving that we have reached quantum degeneracy. We have about 5,000 condensed atoms in our optical dipole trap at a temperature less than 100 nK. The remaining atoms are thermal. Bose-Einstein condensation is obtained within 8 s, and we can repeat the experiment every 30 s. It should be mentioned that the Bose-Einstein experiment was moved from the ”Leibniz Universität Hannover” to the ”Technische Universität Darmstadt”, and had to be completely rebuilt. All-optical Bose-Einstein condensation was reached within one year after the move. Our Bose-Einstein condensation setup presents an ideal starting point for using our condensates in combination with miniaturized atom optical setups based on our novel microfabricated optical elements. With our microlenses, we can create a number of possible dipole trap configurations, such as the dipole trap array or the cylindrical microlens array. Using microlenses in miniaturized atom optical setups opens a completely new field of coherent atom optics. Also because the tight confinement of the microtraps allows us to load a 3D BEC, a 1D BEC, or a Tonks-Girardeau gas in the micropotentials depending on the density.

•Jan 1, 2008•1 citation

All-Optical Production of Quantum Degeneracy and Molecular Bose-Einstein Condensation of 6 Li

Shu-Jin Deng, Peng-Peng Diao, Qian-Li Yu +1 more

We achieve a highly degenerate and strongly interacting Fermi gas in a mixture of the two lowest hyperfine states of 6 Li by direct evaporative cooling in a high power crossed optical dipole trap. The trap is loaded from a large atom number magneto-optical trap realized by a laser system of 2.5-W intracavity-frequency-doubled light output at 671 nm. With this system, we also demonstrate the production of a molecular Bose-Einstein condensate (mBEC) of 6 Li 2 , and observe the anisotropic expansion of Fermi gases in the so-called BEC-Bardeen-Cooper-Schrieffer crossover regime.

arXiv:1502.00280•Chinese Physics Letters•May 1, 2015•13 citations

An apparatus for the production of molecular Bose-Einstein condensates

Thomas Lompe

This thesis reports on the construction of an apparatus capable of producing a molecular Bose-Einstein-Condensate (BEC) of 6Li2. To create a condensate fermionic lithium is first evaporated in an oven, slowed by a Zeeman slower and captured in a magneto-optical-trap (MOT). A scheme for creating time-averaged arbitrary optical potentials for optimized transfer of the atoms from the MOT to a high-power, far detuned optical dipole trap was implemented, as well as magnetic field coils to tune the interactions of the atoms via Feshbach resonances. The first experiments with the new machine include the characterization of the optical dipole trap and evaporative cooling of 6Li.

•Jan 1, 2008•1 citation

All-Optical Formation of an Atomic Bose-Einstein Condensate

M. D. Barrett, J. A. Sauer, Michael Chapman

We have created a Bose-Einstein condensate (BEC) of ${}^{87}\mathrm{Rb}$ atoms directly in an optical trap. We employ a quasielectrostatic dipole force trap formed by two crossed ${\mathrm{CO}}_{2}$ laser beams. Loading directly from a sub-Doppler laser-cooled cloud of atoms results in initial phase space densities of $\ensuremath{\sim}1/200$. Evaporatively cooling through the BEC transition is achieved by lowering the power in the trapping beams over $\ensuremath{\sim}2\mathrm{s}$. The resulting condensates are $F\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1$ spinors with $3.5\ifmmode\times\else\texttimes\fi{}{10}^{4}$ atoms distributed between the ${m}_{F}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(\ensuremath{-}1,0,1)$ states.

arXiv:cond-mat/0106027•Physical Review Letters•Jun 19, 2001•635 citations
We create Bose-Einstein condensates of6Li2molecules in an all-optical setup using a low power (25 W) crossed dipole trap. Our system contains a number of simplifications compared to existing setups and offers a high degree of flexibility in the trapping geometry. We will present our latest results and report on progress towards making p-wave Feshbach molecules.
This thesis describes the production of molecular Bose-Einstein condensates (BEC) of 6Li2 dimers and binding energy measurements of p-wave Feshbach molecules. A σ− Zeeman slower is used to produce a continuous beam of isotopically enriched 6Li atoms at speeds low enough to load a magneto-optical trap (MOT). We currently have a flux of slowed atoms of ~ 5 · 106 atoms/s loading the MOT with more than 108 atoms. We then transfer up to 106 atoms in an almost equal spin mixture of the two lowest hyperfine states into an optical dipole trap. We achieved condensates in three different crossed optical dipole trap geometries. The initial low power optical dipole trap was formed using light from a 25WVersaDisk Yb:YAG laser at 1030 nm. It consisted of a 15 W beam crossed with a 13 W beam at about 80 degrees with a waist of approximately 30 μm in each beam. By translating the focus of the second beam we could change the trap geometry from near symmetric to elongated. Nowadays, we produce condensates in a crossed dipole trap formed by a 100 W fibre laser. Both arms are focussed to a waist of 40 μm, cross each other at 14 degrees and have laser powers of ~80 W and ~70 W, respectively. Evaporative cooling is achieved by reducing the laser power near the broad s-wave Feshbach resonance at 834 G. By tuning to the low magnetic field side (770 G) of the Feshbach resonance molecules are formed through three-body recombination at sufficiently low temperatures. Further evaporation leads to the creation of a molecular BEC. After reducing the laser power by a factor of about 1000 in approximately 3 s we have observed more than 30 000 condensed molecules. During the evaporation the temperature decreases from about 100 μK to below 100 nK. We present measurements of the binding energies of 6Li p-wave Feshbach molecules formed in combinations of the |F = 1/2,mF = +1/2i (|1i) and |F = 1/2,mF = −1/2i (|2i) states. The binding energies scale linearly with magnetic field detuning for all three resonances. The relative molecular magnetic moments are found to be 113 ± 7 μK/G, 111 ± 6 μK/G and 118 ± 8 μK/G for the |1i − |1i, |1i − |2i and |2i − |2i resonances, respectively, in good agreement with theoretical predictions.
In 1925, Einstein predicted the condensation of bosons into the ground state of the system for low (but finite) temperatures. Several phenomena, including superfluidity and superconductivity have been associated with Bose-Einstein condensation, but these systems interact strongly with their environment and pure Bose-Einstein condensation could not be established. It took 70 years, in which time the laser was discovered, and laser cooling techniques to manipulate atoms in a dilute atomic gas, before Bose-Einstein condensation in dilute atomic gases could be demonstrated in 1995. In the first condensation experiments, BECs were created in a magnetic trap. Since in a magnetic trap not all mF states of the atom can be trapped simultaneously, thereby limiting the number of experiments that can be done, other ways of trapping and generating BECs were sought and found. In 2001, the first all-optical BEC was made, where the dipole force was used to trap atoms in the crossing of two far red detuned laser beams. In an optical dipole trap not only atoms in different internal states can be trapped, but also different atomic species simultaneously. In this thesis, the formation of an all-optical Bose-Einstein condensate with rubidium atoms is presented. Conventional all-optical BECs are usually created in high power CO2 laser dipole traps, or have complicated laser cooling schemes and complex dipole trap setups. In our simple and straightforward setup, we load rubidium atoms from a magneto-optical trap into a crossed optical dipole trap created by a single frequency Yb:YAG laser with a wavelength at 1030 nm. The small wavelength allows for a small diffraction limit, and permits us to use standard optical materials, thus making the experimental setup cost effective. Other attempts to achieve Bose-Einstein condensation in a multi-mode (frequency) fiber laser at 1064 nm failed, because the atom loss was quite high. It is assumed that the multi-mode character of the fiber laser induces Raman transitions in rubidium atoms, thereby heating them. We can trap about ∼ 5E7 atoms in a single beam dipole trap out of ∼ 5E9 atoms trapped in theMOT, and ∼ 350,000 atoms can be trapped in a crossed beam dipole trap due to the smaller trap volume. 70% of the atoms in the dipole trap is optically pumped into one mF state. Quantum degeneracy is reached by evaporatively cooling the atoms in the crossed dipole trap by ramping down the laser power with three linear ramps. We can independently change the power of each beam by an AOM. This allows us to use one beam as an atom waveguide for future experiments. After evaporation, we typically have about 10,000 atoms at a temperature below the critical temperature. We have proved Bose-Einstein condensation by using the anisotropic expansion of a quantum degenerate gas trapped in an anisotropic potential. The aspect ratio of our atom cloud changed during a time of flight from 0.7 to 1.2 in 10 ms, thus proving that we have reached quantum degeneracy. We have about 5,000 condensed atoms in our optical dipole trap at a temperature less than 100 nK. The remaining atoms are thermal. Bose-Einstein condensation is obtained within 8 s, and we can repeat the experiment every 30 s. It should be mentioned that the Bose-Einstein experiment was moved from the ”Leibniz Universität Hannover” to the ”Technische Universität Darmstadt”, and had to be completely rebuilt. All-optical Bose-Einstein condensation was reached within one year after the move. Our Bose-Einstein condensation setup presents an ideal starting point for using our condensates in combination with miniaturized atom optical setups based on our novel microfabricated optical elements. With our microlenses, we can create a number of possible dipole trap configurations, such as the dipole trap array or the cylindrical microlens array. Using microlenses in miniaturized atom optical setups opens a completely new field of coherent atom optics. Also because the tight confinement of the microtraps allows us to load a 3D BEC, a 1D BEC, or a Tonks-Girardeau gas in the micropotentials depending on the density.
We achieve a highly degenerate and strongly interacting Fermi gas in a mixture of the two lowest hyperfine states of 6 Li by direct evaporative cooling in a high power crossed optical dipole trap. The trap is loaded from a large atom number magneto-optical trap realized by a laser system of 2.5-W intracavity-frequency-doubled light output at 671 nm. With this system, we also demonstrate the production of a molecular Bose-Einstein condensate (mBEC) of 6 Li 2 , and observe the anisotropic expansion of Fermi gases in the so-called BEC-Bardeen-Cooper-Schrieffer crossover regime.
This thesis reports on the construction of an apparatus capable of producing a molecular Bose-Einstein-Condensate (BEC) of 6Li2. To create a condensate fermionic lithium is first evaporated in an oven, slowed by a Zeeman slower and captured in a magneto-optical-trap (MOT). A scheme for creating time-averaged arbitrary optical potentials for optimized transfer of the atoms from the MOT to a high-power, far detuned optical dipole trap was implemented, as well as magnetic field coils to tune the interactions of the atoms via Feshbach resonances. The first experiments with the new machine include the characterization of the optical dipole trap and evaporative cooling of 6Li.
We have created a Bose-Einstein condensate (BEC) of 87Rb{}^{87}\mathrm{Rb}87Rb atoms directly in an optical trap. We employ a quasielectrostatic dipole force trap formed by two crossed CO2{\mathrm{CO}}_{2}CO2​ laser beams. Loading directly from a sub-Doppler laser-cooled cloud of atoms results in initial phase space densities of $\ensuremath{\sim}1/200$. Evaporatively cooling through the BEC transition is achieved by lowering the power in the trapping beams over $\ensuremath{\sim}2\mathrm{s}$. The resulting condensates are F=1F\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1F=1 spinors with $3.5\ifmmode\times\else\texttimes\fi{}{10}^{4}$ atoms distributed between the ${m}_{F}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(\ensuremath{-}1,0,1)$ states.