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Developments in optical trapping

Carl Wieman

Published May 21, 1990• 0 citations
OpenAlex

Abstract

The Zeeman shift spontaneous force trap1,2 has been a major advance in the optical trapping of neutral atoms. More than 108 atoms have been trapped, and storage times of minutes have been achieved. We have trapped cesium using inexpensive low power diode lasers, which demonstrates that optical trapping technology can be relatively accessible. As a further step in this direction we trapped atoms in the middle of a low pressure (10−7-10−8-Torr) cesium vapor cell.

Related papers

Cooling and trapping atoms using diode lasers

Carl Wieman

There has been considerable activity recently on cooling and trapping atoms using laser light. This work raises expectations that laser manipulation of atoms will be an important new tool for atomic physics. However, up to now, almost all the work has been on sodium atoms using light from dye lasers. The expense and complication of a narrowband dye laser system is a considerable limitation on the possible uses of this tool. In response to this we have been exploring the use of inexpensive diode lasers for the manipulation of atoms. We have found that diode lasers work very well for this purpose and even have some advantages over dye lasers in addition to cost and ease of use. We previously reported using light from diode lasers to stop a beam of atomic cesium. Here we discuss our more recent work using diode lasers to produce extremely cold cesium vapor via optical molasses cooling and the demonstration of a new type of optical trap. This is a purely optical spontaneous force trap which uses spatially inhomogeneous optical pumping to circumvent the optical Earnshaw theorem.

Annual Meeting Optical Society of America•Jan 1, 1987•0 citations

A long-lived neutral atom trap

Kenneth G. Libbrecht, Phil A. Willems

We have constructed a Zeemanshift Optical Trap (ZOT) for neutral cesium atoms within a sealed cryostat cooled to 4.2K. The low residual background pressure of these temperatures, plus low velocities and masses of the background molecules (mostly He and H{sub 2}), leads to an exceptionally long holding time for trapped Cs atoms in the ZOT. In our initial attempts we measured trap holding times {approximately}5-10 minutes, but increasing this to several hours should be possible. Our latest experimental results will be presented. Long trap holding times may be useful for achieving a Bose condensed gas via evaporative cooling, since thermal relaxation times are fairly long and background gas collisions are therefore important. We are also beginning experiments to trap atoms with superconducting coils inside the cryostat. Our initial aim is to construct microscopic neutral atom traps and other structures with large magnetic field gradients (as high as 10{sup 8} G/cm), where the {triangledown}({rvec {mu}}{center_dot}{rvec B}) force is much greater than has been realized in previous trapping geometries.

Bulletin of the American Physical Society•May 1, 1993•0 citations

Curious behavior of optically trapped neutral atoms

Carl Wieman, Thad G Walker, David W. Sesko +1 more

We have studied the behavior of clouds of neutral atoms contained in a spontaneous force optical trap. Because of the low temperatures of the atoms (<1 mK) we have observed a variety of new phenomena which involve both short and long range interactions between the atoms. The short range interactions are manifested in two body collisions which are notable because of the very long collision times. This time scale causes the dynamics to be profoundly affected by absorption and spontaneous emission during the collision. An interesting assortment of collective behaviors are observed when the trapped atom cloud contains more than 105 atoms. These include the expansion of the cloud as the number is increased and dramatic changes in the distribution of the atoms at higher numbers. We can explain much of the collective behavior using a simple model that includes a 1/r2 force between the atoms arising from the multiple scattering of photons. Finally, we discuss the optical trapping of atoms directly from a low pressure vapor in a small glass cell. We have used these optically trapped atoms to load a magnetostatic trap in the same cell. This provided a high density sample of atoms with a temperature of less than 2 μK.

AIP conference proceedings•Jan 1, 1991•0 citations

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We have produced a very cold sample of spin-polarized trapped atoms. The technique used dramatically simplifies the production of laser-cooled atoms. In this experiment, 1.8\ifmmode\times\else\texttimes\fi{}${10}^{7}$ neutral cesium atoms were optically captured directly from a low-pressure vapor in a small glass cell. We then cooled the 1-${\mathrm{mm}}^{3}$ cloud of trapped atoms and loaded it into a low-field magnetic trap in the same cell. The magnetically trapped atoms had an effective temperature as low as 1.1\ifmmode\pm\else\textpm\fi{}0.2 \ensuremath{\mu}K, which is the lowest kinetic temperature ever observed and far colder than any previous sample of trapped atoms.

Physical Review Letters•Sep 24, 1990•653 citations

Improved magneto-optic trapping in a vapor cell

Kurt Gibble, Steven Kasapi, Steven Chu

We have captured 3.6 x 10(10) cesium atoms in a magneto-optic trap loaded from a vapor cell. The 300-fold increase in the number of trapped atoms compared with that of previous research was accomplished by using larger laser intensities and 4-cm-diameter laser beams. The loading time constant was as short as 0.2 s.

Optics Letters•Apr 1, 1992•159 citations

Experimental and theoretical study of the vapor-cell Zeeman optical trap

K. Lindquist, Michelle S. Stephens, Carl Wieman

We present an experimental study of the number and density of trapped atoms in a vapor-cell Zeeman optical trap. We have investigated how the number (and therefore the capture rate) and density change with the trapping laser's beam diameter, intensity, and detuning and with the magnetic-field gradient of the trap. We have developed a quasi-one-dimensional numerical model that accurately predicts the number of trapped atoms for all conditions. We also have investigated chirping the laser frequency and trapping with broadband light, neither of which increase the number of trapped atoms.

Physical Review A•Oct 1, 1992•182 citations
The Zeeman shift spontaneous force trap1,2 has been a major advance in the optical trapping of neutral atoms. More than 108 atoms have been trapped, and storage times of minutes have been achieved. We have trapped cesium using inexpensive low power diode lasers, which demonstrates that optical trapping technology can be relatively accessible. As a further step in this direction we trapped atoms in the middle of a low pressure (10−7-10−8-Torr) cesium vapor cell.
There has been considerable activity recently on cooling and trapping atoms using laser light. This work raises expectations that laser manipulation of atoms will be an important new tool for atomic physics. However, up to now, almost all the work has been on sodium atoms using light from dye lasers. The expense and complication of a narrowband dye laser system is a considerable limitation on the possible uses of this tool. In response to this we have been exploring the use of inexpensive diode lasers for the manipulation of atoms. We have found that diode lasers work very well for this purpose and even have some advantages over dye lasers in addition to cost and ease of use. We previously reported using light from diode lasers to stop a beam of atomic cesium. Here we discuss our more recent work using diode lasers to produce extremely cold cesium vapor via optical molasses cooling and the demonstration of a new type of optical trap. This is a purely optical spontaneous force trap which uses spatially inhomogeneous optical pumping to circumvent the optical Earnshaw theorem.
We have constructed a Zeemanshift Optical Trap (ZOT) for neutral cesium atoms within a sealed cryostat cooled to 4.2K. The low residual background pressure of these temperatures, plus low velocities and masses of the background molecules (mostly He and H{sub 2}), leads to an exceptionally long holding time for trapped Cs atoms in the ZOT. In our initial attempts we measured trap holding times {approximately}5-10 minutes, but increasing this to several hours should be possible. Our latest experimental results will be presented. Long trap holding times may be useful for achieving a Bose condensed gas via evaporative cooling, since thermal relaxation times are fairly long and background gas collisions are therefore important. We are also beginning experiments to trap atoms with superconducting coils inside the cryostat. Our initial aim is to construct microscopic neutral atom traps and other structures with large magnetic field gradients (as high as 10{sup 8} G/cm), where the {triangledown}({rvec {mu}}{center_dot}{rvec B}) force is much greater than has been realized in previous trapping geometries.
We have studied the behavior of clouds of neutral atoms contained in a spontaneous force optical trap. Because of the low temperatures of the atoms (<1 mK) we have observed a variety of new phenomena which involve both short and long range interactions between the atoms. The short range interactions are manifested in two body collisions which are notable because of the very long collision times. This time scale causes the dynamics to be profoundly affected by absorption and spontaneous emission during the collision. An interesting assortment of collective behaviors are observed when the trapped atom cloud contains more than 105 atoms. These include the expansion of the cloud as the number is increased and dramatic changes in the distribution of the atoms at higher numbers. We can explain much of the collective behavior using a simple model that includes a 1/r2 force between the atoms arising from the multiple scattering of photons. Finally, we discuss the optical trapping of atoms directly from a low pressure vapor in a small glass cell. We have used these optically trapped atoms to load a magnetostatic trap in the same cell. This provided a high density sample of atoms with a temperature of less than 2 μK.
We have produced a very cold sample of spin-polarized trapped atoms. The technique used dramatically simplifies the production of laser-cooled atoms. In this experiment, 1.8\ifmmode\times\else\texttimes\fi{}107{10}^{7}107 neutral cesium atoms were optically captured directly from a low-pressure vapor in a small glass cell. We then cooled the 1-mm3{\mathrm{mm}}^{3}mm3 cloud of trapped atoms and loaded it into a low-field magnetic trap in the same cell. The magnetically trapped atoms had an effective temperature as low as 1.1\ifmmode\pm\else\textpm\fi{}0.2 \ensuremath{\mu}K, which is the lowest kinetic temperature ever observed and far colder than any previous sample of trapped atoms.
We present an experimental study of the number and density of trapped atoms in a vapor-cell Zeeman optical trap. We have investigated how the number (and therefore the capture rate) and density change with the trapping laser's beam diameter, intensity, and detuning and with the magnetic-field gradient of the trap. We have developed a quasi-one-dimensional numerical model that accurately predicts the number of trapped atoms for all conditions. We also have investigated chirping the laser frequency and trapping with broadband light, neither of which increase the number of trapped atoms.