OSA's Digital Library

Journal of the Optical Society of America B

Journal of the Optical Society of America B


  • Vol. 16, Iss. 5 — May. 1, 1999
  • pp: 702–709

Compression of a cold atomic cloud by on-resonance laser light

Lev Khaykovich and Nir Davidson  »View Author Affiliations

JOSA B, Vol. 16, Issue 5, pp. 702-709 (1999)

View Full Text Article

Acrobat PDF (259 KB)

Browse Journals / Lookup Meetings

Browse by Journal and Year


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools



We analyze the light-induced atom–atom interactions in optically thick atomic clouds and show that, when the laser frequency is on-resonance with the atomic transition, they become attractive. On the basis of this analysis we propose and demonstrate a novel scheme to compress a cold and dense atomic cloud with a short on-resonance laser pulse. The compression force arises from attenuation of the laser light by the atomic cloud. The following free propagation of the atoms shows a lenslike behavior that yields a transient density increase at the focal time, where neither laser nor magnetic field perturbations exist. A cooling pulse, which is applied at the focal time of this lens, restores the initial temperature of atoms, and hence the phase space density is increased. Finally, we adopt our compression scheme to a quasi-steady-state mode by temporally chopping it with the cooling and trapping beams of a magnet-optical trap.

© 1999 Optical Society of America

OCIS Codes
(140.3320) Lasers and laser optics : Laser cooling
(140.7010) Lasers and laser optics : Laser trapping

Lev Khaykovich and Nir Davidson, "Compression of a cold atomic cloud by on-resonance laser light," J. Opt. Soc. Am. B 16, 702-709 (1999)

Sort:  Author  |  Year  |  Journal  |  Reset


  1. E. L. Raab, M. Prentiss, A. Cable, S. Chu, and D. E. Pritchard, “Trapping of neutral sodium atoms with radiation pressure,” Phys. Rev. Lett. 59, 2631 (1987).
  2. See special issue on laser cooling and trapping of atoms, S. Chu and C. E. Wieman, eds., J. Opt. Soc. Am. B 6, 2020 (1989).
  3. D. Sesko, T. Walker, and C. Wieman, “Behavior of neutral atoms in a spontaneous force trap,” J. Opt. Soc. Am. B 8, 946 (1991).
  4. J. Dalibard, “Laser cooling of an optically thick gas: the simplest radiation pressure trap?” Opt. Commun. 68, 203 (1988).
  5. A. P. Kazantsev, G. I. Surdutovich, D. O. Chudesnikov, and V. P. Yakovlev, “Scattering, velocity bunching, and self-localization of atoms in a light field,” J. Opt. Soc. Am. B 6, 2130 (1989).
  6. W. Petrich, M. H. Anderson, J. R. Ensher, and E. A. Cornell, “Behavior of atoms in a compressed magneto-optical trap,” J. Opt. Soc. Am. B 11, 1332 (1994).
  7. W. Ketterle, K. B. Davis, M. A. Joffe, A. Martin, and D. E. Pritchard, “High density of cold atoms in a dark spontaneous-force optical trap,” Phys. Rev. Lett. 70, 2253 (1993).
  8. C. G. Townsend, N. H. Edwards, K. P. Zetie, C. J. Cooper, J. Rink, and C. J. Foot, “High-density trapping of cesium atoms in a dark magneto-optical trap,” Phys. Rev. A 53, 1702 (1996).
  9. C. G. Townsend, N. H. Edwards, C. G. Cooper, K. P. Zetie, C. J. Foot, A. M. Steane, P. Szriftgiser, H. Perrin, and J. Dalibard, “Phase-space density in the magneto-optical trap,” Phys. Rev. A 52, 1423 (1995).
  10. These changes also affect the spring constant, as shown by A. Steane, M. Chowdhury, and C. Foot, “Radiation force in the magneto-optical trap,” J. Opt. Soc. Am. B 9, 2142 (1992).
  11. See, for instance, evaporative cooling in N. Masuhara, J. M. Doyle, J. C. Sandberg, D. Kleppner, T. J. Greytak, H. F. Hess, and G. P. Kochanski, “Evaporative cooling of spin-polarized atomic hydrogen,” Phys. Rev. Lett. 61, 935 (1988), or Raman cooling in H. J. Lee, C. S. Adams, M. Kasevich, and S. Chu, “Raman cooling of atoms in an optical dipole trap,” Phys. Rev. Lett. 76, 2658 (1996).
  12. B. R. Mollow, “Power spectrum of light scattered by two-level system,” Phys. Rev. 188, 1969 (1969).
  13. B. R. Mollow, “Stimulated emission and absorption near resonance for driven system,” Phys. Rev. A 5, 2217 (1972).
  14. After scattering of a few photons, optical pumping aligns each atom with respect to the linearly polarized laser light. For this situation the saturation intensity for rubidium is Isat=3 mW/cm2 instead of 1.65 mW/cm2 for a completely polarized atom. It is also nearly uniform among the three occupied m states. Throughout the paper we scale intensities to this Isat despite different experimental situations.
  15. We assume a uniform spatial distribution of the atoms over the period of the standing wave. This is applicable to the on-resonance case (δ=0), whereas at δ≠0 some localization of the atoms toward the nodes (δ>0) and the antinodes (δ<0) of the standing wave is expected owing to the dipole force. We neglect this localization here.
  16. A. Fioretti, A. F. Molisch, J. H. Müller, P. Verkerk, and M. Allegrini, “Observation of radiation trapping in a dense Cs magneto-optical trap,” Opt. Commun. 149, 415 (1998).
  17. At low intensities the neglect of the repulsive inter-atomic forces by our simplified model is not justified anyway.
  18. To calculate Caverage, we extended the simulations to a two-dimensional Gaussian density distribution n(x, y, z=0), and the one-dimensional integrated density was defined as ∫n(x, y, z=0)dy, corresponding to our imaging fluorescence measurements that are described below.
  19. P. D. Lett, R. N. Watts, C. I. Westbrook, W. D. Phillips, P. L. Gould, and H. J. Metcalf, “Observation of atoms laser cooled below the Doppler limit,” Phys. Rev. Lett. 61, 169 (1988).
  20. We observed nearly identical dependence on laser detuning in one-beam and six-beam configurations.
  21. Note that for the pulsed compression the optimal compression was obtained for detuning of 1–2 MHz above resonance (see inset of Fig. 7). This frequency shift can be explained by the fact that when the atoms are accelerated during the ~100-μs compression pulses they acquire a negative Doppler shift of a few megahertz, so their average detuning is close to zero when their initial detuning is somewhat posi-tive. This does not apply for the quasi steady state of Fig. 9, as is confirmed by the exact zero location of the optimal detuning.
  22. D. Boiron, A. Michaud, J. M. Fournier, L. Simard, M. Sprenger, G. Grinberg, and C. Salomon, “Cold and dense cesium clouds in far-detuned dipole traps,” Phys. Rev. A 57, R4106 (1998).
  23. L. Khaykovich, N. Friedman, and N. Davidson, “Saturation of the weak probe amplification in a strongly driven cold and dense atomic cloud,” Europhys. J. (to be published).

Cited By

Alert me when this paper is cited

OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.

« Previous Article  |  Next Article »

OSA is a member of CrossRef.

CrossCheck Deposited