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Title: Nondestructive interferometric characterization of an optical dipole trap

Abstract

A method for nondestructive characterization of a dipole-trapped atomic sample is presented. It relies on a measurement of the phase shift imposed by cold atoms on an optical pulse that propagates through a free-space Mach-Zehnder interferometer. Using this technique we are able to determine, with very good accuracy, relevant trap parameters such as the atomic sample temperature, trap oscillation frequencies, and loss rates. Another important feature is that our method is faster than conventional absorption or fluorescence techniques, allowing the combination of high-dynamical range measurements and a reduced number of spontaneous emission events per atom.

Authors:
; ; ; ;  [1]
  1. QUANTOP, Danish National Research Foundation Centre of Quantum Optics, Niels Bohr Institute, DK-2100 Copenhagen O (Denmark)
Publication Date:
OSTI Identifier:
20982394
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. A; Journal Volume: 75; Journal Issue: 3; Other Information: DOI: 10.1103/PhysRevA.75.033803; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; ABSORPTION; ATOMS; DIPOLES; FLUORESCENCE; LOSSES; MACH-ZEHNDER INTERFEROMETER; OPTICS; OSCILLATIONS; PHASE SHIFT; PULSES; RADIATION PRESSURE; TRAPPING; TRAPS

Citation Formats

Petrov, Plamen G., Oblak, Daniel, Alzar, Carlos L. Garrido, Kjaergaard, Niels, and Polzik, Eugene S. Nondestructive interferometric characterization of an optical dipole trap. United States: N. p., 2007. Web. doi:10.1103/PHYSREVA.75.033803.
Petrov, Plamen G., Oblak, Daniel, Alzar, Carlos L. Garrido, Kjaergaard, Niels, & Polzik, Eugene S. Nondestructive interferometric characterization of an optical dipole trap. United States. doi:10.1103/PHYSREVA.75.033803.
Petrov, Plamen G., Oblak, Daniel, Alzar, Carlos L. Garrido, Kjaergaard, Niels, and Polzik, Eugene S. Thu . "Nondestructive interferometric characterization of an optical dipole trap". United States. doi:10.1103/PHYSREVA.75.033803.
@article{osti_20982394,
title = {Nondestructive interferometric characterization of an optical dipole trap},
author = {Petrov, Plamen G. and Oblak, Daniel and Alzar, Carlos L. Garrido and Kjaergaard, Niels and Polzik, Eugene S.},
abstractNote = {A method for nondestructive characterization of a dipole-trapped atomic sample is presented. It relies on a measurement of the phase shift imposed by cold atoms on an optical pulse that propagates through a free-space Mach-Zehnder interferometer. Using this technique we are able to determine, with very good accuracy, relevant trap parameters such as the atomic sample temperature, trap oscillation frequencies, and loss rates. Another important feature is that our method is faster than conventional absorption or fluorescence techniques, allowing the combination of high-dynamical range measurements and a reduced number of spontaneous emission events per atom.},
doi = {10.1103/PHYSREVA.75.033803},
journal = {Physical Review. A},
number = 3,
volume = 75,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}
  • The effect of the dipole-dipole interaction on the far-off-resonance optical dipole trapping scheme is calculated by a mean-field approach. The trapping laser field polarizes the atoms and the accompanying dipole-dipole energy shift deepens the attractive potential minimum in a pancake-shaped cloud. At high density the thermal motion cannot stabilize the gas against self-contraction and an instability occurs. We calculate the boundary of the stable and unstable equilibrium regions on a two-dimensional phase diagram of the atom number and the ratio of the trap depth to the temperature. We discuss the limitations imposed by the dipole-dipole instability on the parameters neededmore » to reach Bose-Einstein condensation in an optical dipole trap.« less
  • We extend the technique originally proposed by [Honda et al., Phys. Rev. A 59, R934 (1999)] to measure the temperature of ytterbium and alkaline-earth-metal atoms confined in a magneto-optical trap (MOT). The method is based on the analysis of excitation spectra obtained by probing the {sup 1}S{sub 0}{yields}{sup 3}P{sub 1} intercombination line. Thanks to a careful analysis and modeling of the effects caused by the MOT light on the probe transition we overcome the resolution and precision limits encountered in previous works. Ground-state light shift and Rabi broadening are measured and successfully compared with calculated values. This knowledge allows usmore » to properly extract the Doppler contribution to the linewidth, thus obtaining a reliable measurement of the cloud temperature. We finally show how spectroscopy on free-falling atoms provides an alternative method to determine the sample temperature which resembles the standard time-of-flight technique.« less
  • Optical dipole traps can provide strong, state-independent confinement of atoms. Unfortunately, the spatially dependent light shifts of optical transitions in dipole traps can interfere with conventional laser cooling techniques. These limitations may be overcome by cooling trapped atoms with stimulated Raman transitions. In particular, the lights shifts of ground state sublevels can be equal, so that the Raman cooling transition is unperturbed. Cooling in the sideband limit, to the quantum ground state of motion, should be possible. We have confined {sup 85}Rb atoms in a far-detuned optical dipole trap, and indirectly measured extremely low heating rates of the trapped atoms.more » We have also driven velocity-sensitive stimulated Raman transitions of the trapped atoms. The high resolution of these stimulated Raman resonances should allow us to resolve the motional sidebands and to directly cool the trapped atoms.« less
  • We have confined up to 10{sup 4} {sup 85}Rb atoms in an optical dipole force trap operating up to 65 nm from atomic resonance. For detunings greater than 16 nm, we obtained long confinement times, limited only by background gas collisions, without additional cooling. However, for trapping laser tunings between 4 nm and 16 nm to the red of the lowest Rb (D1) resonance, we observed a novel trap loss mechanism which results in much shorter-trap lifetimes. The trap loss rate is very sensitive to the laser wavelength, and exhibits a complex spectrum. This trap loss may arise from amore » photo-associative collisional process in which an initially free pair of colliding ground state atoms is promoted to a bound molecular excited state. The bound excited molecule could then be lost from the trap by photoionization, or by spontaneous decay to an untrapped ground state. The results of our preliminary experiments and of further experiments to clarify this novel trap loss process will be presented.« less
  • We have Raman cooled sodium atoms below the photon recoil temperature in a novel type of blue-detuned optical dipole force trap. In this trap 4.5{times}10{sup 5} atoms have been cooled to an effective three dimensional temperature of 1.0 {mu}K at a final density of 4{times}10{sup 11} cm{sup {minus}3}. No atoms were lost during the cooling process. The phase space density increased by a factor of 320 over the uncooled sample. This is the highest phase space density achieved by an all-optical cooling method. {copyright} {ital 1996 The American Physical Society.}