Toward an atom laser: Cold atoms in a long, high-gradient magnetic guide

The continuous injection and propagation of a cold atomic beam in a 1.7 m long high-gradient (up to 2.7 kG/cm) magnetic guide is demonstrated. Continuous injection is accomplished by side-loading a magnetic guide with atoms from a sequence of two modified magneto-optical traps. In the high-gradient portion of the guide, the guided atomic beam has a transverse temperature of 420 muK +/- 40 muK, a longitudinal temperature of 1 mK, and an average velocity of order 1 m/s. Essential for the characterization of this steady-state atomic beam, imaging methods compatible with the high field-gradients associated with this magnetic guide have been investigated and developed. By utilizing a probe laser tuned to an open transition, the fluorescence yield per atom is largely fixed throughout the trap volume, independent of the trapping field. This enables a reliable conversion of fluorescence images into atomic-density profiles. Using a fixed radio-frequency (nurf) current coupled directly onto the guide wires, continuous and selective removal of atoms with a transverse energy exceeding hnurf is demonstrated. This removal scheme is the essence of an rf filter, where the number of modes occupied by the atomic flow is reduced. Through sufficient rf-filtering, a near-single-mode guided atomic beam should be achievable, enabling basic atom-interferometric experiments. The extension of this fixed-frequency removal of atoms for continuous position-resolved evaporative cooling in a long magnetic guide is outlined. Employing an innovative gridless technique for performing Direct Simulation of rarefied gas dynamics via Monte Carlo (DSMC), the evaporative cooling process in a guided atomic beam has been simulated. Both fixed-frequency as well as variable-frequency evaporative cooling layouts have been explored and the results of these simulations are presented. The implementation of this gridless technique is presented and its benefits are briefly outlined. In parallel with the development of a continuous-wave atom laser, tools suited to manipulate cold atomic beams in atom guides have been explored. An atomic guide with a tunable aspect ratio, using rf-dressed state potentials, is presented.The continuous injection and propagation of a cold atomic beam in a 1.7 m long high-gradient (up to 2.7 kG/cm) magnetic guide is demonstrated. Continuous injection is accomplished by side-loading a magnetic guide with atoms from a sequence of two modified magneto-optical traps. In the high-gradient portion of the guide, the guided atomic beam has a transverse temperature of 420 muK +/- 40 muK, a longitudinal temperature of 1 mK, and an average velocity of order 1 m/s. Essential for the characterization of this steady-state atomic beam, imaging methods compatible with the high field-gradients associated with this magnetic guide have been investigated and developed. By utilizing a probe laser tuned to an open transition, the fluorescence yield per atom is largely fixed throughout the trap volume, independent of the trapping field. This enables a reliable conversion of fluorescence images into atomic-density profiles. Using a fixed radio-frequency (nurf) current coupled directly onto the guide wires, continuous and selective removal of atoms with a transverse energy exceeding hnurf is demonstrated. This removal scheme is the essence of an rf filter, where the number of modes occupied by the atomic flow is reduced. Through sufficient rf-filtering, a near-single-mode guided atomic beam should be achievable, enabling basic atom-interferometric experiments. The extension of this fixed-frequency removal of atoms for continuous position-resolved evaporative cooling in a long magnetic guide is outlined. Employing an innovative gridless technique for performing Direct Simulation of rarefied gas dynamics via Monte Carlo (DSMC), the evaporative cooling process in a guided atomic beam has been simulated. Both fixed-frequency as well as variable-frequency evaporative cooling layouts have been explored and the results of these simulations are presented. The implementation of this gridless technique is presented and its benefits are briefly outlined. In parallel with the development of a continuous-wave atom laser, tools suited to manipulate cold atomic beams in atom guides have been explored. An atomic guide with a tunable aspect ratio, using rf-dressed state potentials, is presented.

Jan 1, 20060 citations

Towards a Steady-state Atom Laser

Chun-Chia Chen, Shayne Bennetts, Rodrigo González Escudero +2 more

Bulletin of the American Physical SocietyMay 28, 20190 citations

Narrow-Line Laser Cooling and Trapping of Strongly Magnetic Atoms

Andrew J. Berglund, James L. Hanssen, Jabez J. McClelland

Bulletin of the American Physical SocietyMay 31, 20080 citations

Continuous propagation and energy filtering of a cold atomic beam in a long high-gradient magnetic atom guide

Spencer E. Olson, Rahul R. Mhaskar, Georg A. Raithel

We demonstrate the continuous injection and propagation of a cold atomic beam in a high-gradient (up to $2.7\phantom{\rule{0.3em}{0ex}}\mathrm{kG}∕\mathrm{cm}$ ) magnetic guide of $1.7\phantom{\rule{0.3em}{0ex}}\mathrm{m}$ length. Continuous injection is accomplished using a side-loading scheme that involves a sequence of two modified magneto-optic traps. Methods are developed to measure the atomic-flow temperatures and the flux under steady-state conditions. In the high-gradient portion of the guide, the guided atomic beam has a transverse temperature of $420\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K}\ifmmode\pm\else\textpm\fi{}40\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K}$, a longitudinal temperature of $1\phantom{\rule{0.3em}{0ex}}\mathrm{mK}$ , and an average velocity of order $1\phantom{\rule{0.3em}{0ex}}\mathrm{m}∕\mathrm{s}$ . Using a radio-frequency current of a fixed frequency $\ensuremath{\nu}$ coupled directly into the guide wires, atoms exceeding a transverse energy of $h\ensuremath{\nu}$ can be continuously and selectively removed from the atomic beam.We demonstrate the continuous injection and propagation of a cold atomic beam in a high-gradient (up to $2.7\phantom{\rule{0.3em}{0ex}}\mathrm{kG}∕\mathrm{cm}$) magnetic guide of $1.7\phantom{\rule{0.3em}{0ex}}\mathrm{m}$ length. Continuous injection is accomplished using a side-loading scheme that involves a sequence of two modified magneto-optic traps. Methods are developed to measure the atomic-flow temperatures and the flux under steady-state conditions. In the high-gradient portion of the guide, the guided atomic beam has a transverse temperature of $420\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K}\ifmmode\pm\else\textpm\fi{}40\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K}$, a longitudinal temperature of $1\phantom{\rule{0.3em}{0ex}}\mathrm{mK}$, and an average velocity of order $1\phantom{\rule{0.3em}{0ex}}\mathrm{m}∕\mathrm{s}$. Using a radio-frequency current of a fixed frequency $\ensuremath{\nu}$ coupled directly into the guide wires, atoms exceeding a transverse energy of $h\ensuremath{\nu}$ can be continuously and selectively removed from the atomic beam.

Physical Review AMar 29, 200629 citations

Experiments in cold atom optics towards precision atom interferometry

David C. Aveline

Atom optics has been a highly active field of research with many scientific breakthroughs over the past two decades, largely due to successful advances in laser technology, microfabrication techniques, and the development of laser cooling and trapping of neutral atoms. This dissertation details several atom optics experiments with the motivation to develop tools and techniques for precision atom wave interferometry. It provides background information about atom optics and the fundamentals behind laser cooling and trapping, including basic techniques for cold gas thermometry and absorptive detection of atoms. A brief overview of magnetic trapping and guiding in tight wire-based traps is also provided before the experimental details are presented. ❧ We developed a novel laser source of 780 nm light using frequency-doubled 1560 nm fiber amplifier. This laser system provided up to a Watt of tunable frequency stabilized light for two Rb laser cooling and trapping experiments. One system generates Bose-Einstein condensates in an optical trap while the second is based on atom chip magnetic traps. The atom chip system, detailed in this thesis, was designed and built to develop the tools necessary for transport and loading large numbers of cold atoms and explore the potential for guided atom interferometry. Techniques and results from this experiment are presented, including an efficient magnetic transport and loading method to deliver cold atom to atom chip traps. We also developed a modeling tool for the magnetic fields formed by coiled wire geometries, as well as planar wire patterns. These models helped us design traps and determine adiabatic transportation of cold atoms between macro-scale traps and micro-traps formed on atom chips. Having achieved near unity transfer efficiency, we demonstrated that this approach promises to be a consistent method for loading large numbers of atoms into micro-traps. Furthermore, we discuss an in situ imaging technique to investigate magnetic field contours of the traps and the dynamics of atoms within those confining potentials. We also controlled the propagation along the atom chip guides by accelerating atoms with longitudinal magnetic gradients, and investigated an atom focusing scheme. ❧ While the atom chip wire guides perform a role analogous to optical fibers guiding light waves, ""free space"" cold atoms offer great opportunity for precision interferometry. We describe a second on-going atom optics experiment that measures gravity gradients using a pair of atom fountain interferometers separated by one meter. We have demonstrated Gravity Gradiometer resolution down to 4x10⁻⁹ g/m using a 40 kg test mass. The atomic physics subsystem is described in detail, including the vacuum, cold atom source, optics, magnetic coils and shields, and vibration isolation and compensation. The system is designed to be a compact, robust, transportable instrument, taking strides towards future gravity gradient measurements in the field. In the realm of space applications, there has been interest for micro-gravity science experiments aboard the International Space Station, along with instrument development for gravity mapping of Earth and planetary bodies with satellite-based instruments. Furthermore, there are ground-based applications for gravity imaging of local density distributions, precision measurement of gravity, as well as proposals for redefining the kilogram, detecting gravitational waves and determining the Gravitational constant.Atom optics has been a highly active field of research with many scientific breakthroughs over the past two decades, largely due to successful advances in laser technology, microfabrication techniques, and the development of laser cooling and trapping of neutral atoms. This dissertation details several atom optics experiments with the motivation to develop tools and techniques for precision atom wave interferometry. It provides background information about atom optics and the fundamentals behind laser cooling and trapping, including basic techniques for cold gas thermometry and absorptive detection of atoms. A brief overview of magnetic trapping and guiding in tight wire-based traps is also provided before the experimental details are presented. ❧ We developed a novel laser source of 780 nm light using frequency-doubled 1560 nm fiber amplifier. This laser system provided up to a Watt of tunable frequency stabilized light for two Rb laser cooling and trapping experiments. One system generates Bose-Einstein condensates in an optical trap while the second is based on atom chip magnetic traps. The atom chip system, detailed in this thesis, was designed and built to develop the tools necessary for transport and loading large numbers of cold atoms and explore the potential for guided atom interferometry. Techniques and results from this experiment are presented, including an efficient magnetic transport and loading method to deliver cold atom to atom chip traps. We also developed a modeling tool for the magnetic fields formed by coiled wire geometries, as well as planar wire patterns. These models helped us design traps and determine adiabatic transportation of cold atoms between macro-scale traps and micro-traps formed on atom chips. Having achieved near unity transfer efficiency, we demonstrated that this approach promises to be a consistent method for loading large numbers of atoms into micro-traps. Furthermore, we discuss an in situ imaging technique to investigate magnetic field contours of the traps and the dynamics of atoms within those confining potentials. We also controlled the propagation along the atom chip guides by accelerating atoms with longitudinal magnetic gradients, and investigated an atom focusing scheme. ❧ While the atom chip wire guides perform a role analogous to optical fibers guiding light waves, ""free space"" cold atoms offer great opportunity for precision interferometry. We describe a second on-going atom optics experiment that measures gravity gradients using a pair of atom fountain interferometers separated by one meter. We have demonstrated Gravity Gradiometer resolution down to 4x10⁻⁹ g/m using a 40 kg test mass. The atomic physics subsystem is described in detail, including the vacuum, cold atom source, optics, magnetic coils and shields, and vibration isolation and compensation. The system is designed to be a compact, robust, transportable instrument, taking strides towards future gravity gradient measurements in the field. In the realm of space applications, there has been interest for micro-gravity science experiments aboard the International Space Station, along with instrument development for gravity mapping of Earth and planetary bodies with satellite-based instruments. Furthermore, there are ground-based applications for gravity imaging of local density distributions, precision measurement of gravity, as well as proposals for redefining the kilogram, detecting gravitational waves and determining the Gravitational constant.

Jan 1, 20151 citation

We demonstrate the continuous injection and propagation of a cold atomic beam in a high-gradient (up to

2.7\phantom{\rule{0.3em}{0ex}}\mathrm{kG}∕\mathrm{cm}

) magnetic guide of

1.7\phantom{\rule{0.3em}{0ex}}\mathrm{m}

length. Continuous injection is accomplished using a side-loading scheme that involves a sequence of two modified magneto-optic traps. Methods are developed to measure the atomic-flow temperatures and the flux under steady-state conditions. In the high-gradient portion of the guide, the guided atomic beam has a transverse temperature of $420\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K}\ifmmode\pm\else\textpm\fi{}40\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K}$, a longitudinal temperature of

1\phantom{\rule{0.3em}{0ex}}\mathrm{mK}

, and an average velocity of order

1\phantom{\rule{0.3em}{0ex}}\mathrm{m}∕\mathrm{s}

. Using a radio-frequency current of a fixed frequency $\ensuremath{\nu}$ coupled directly into the guide wires, atoms exceeding a transverse energy of $h\ensuremath{\nu}$ can be continuously and selectively removed from the atomic beam.