Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Laser cooling by collisional redistribution of radiation


The general idea that optical radiation may cool matter was put forward 80 years ago1. Doppler cooling of dilute atomic gases is an extremely successful application of this concept2,3. More recently, anti-Stokes cooling in multilevel systems has been explored4,5, culminating in the optical refrigeration of solids6,7,8,9. Collisional redistribution of radiation has been proposed10 as a different cooling mechanism for atomic two-level systems, although experimental investigations using moderate-density gases have not reached the cooling regime11. Here we experimentally demonstrate laser cooling of an atomic gas based on collisional redistribution of radiation, using rubidium atoms in argon buffer gas at a pressure of 230 bar. The frequent collisions in the ultradense gas transiently shift a highly red-detuned laser beam (that is, one detuned to a much lower frequency) into resonance, whereas spontaneous decay occurs close to the unperturbed atomic resonance frequency. During each excitation cycle, kinetic energy of order kBT—that is, the thermal energy (kB, Boltzmann’s constant; T, temperature)—is extracted from the dense atomic sample. In a proof-of-principle experiment with a thermally non-isolated sample, we demonstrate relative cooling by 66 K. The cooled gas has a density more than ten orders of magnitude greater than the typical values used in Doppler-cooling experiments, and the cooling power reaches 87 mW. Future applications of the technique may include supercooling beyond the homogeneous nucleation temperature12,13 and optical chillers9.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Rent or buy this article

Get just this article for as long as you need it


Prices may be subject to local taxes which are calculated during checkout

Figure 1: Cooling principle and set-up.
Figure 2: Experimental spectra.
Figure 3: Thermographic image.
Figure 4: Measurement of temperature inside the cell.


  1. Pringsheim, P. Zwei Bemerkungen über den Unterschied von Lumineszenz- und Temperaturstrahlung. Z. Phys. 57, 739–746 (1929)

    Article  ADS  CAS  Google Scholar 

  2. Hänsch, T. W. & Schawlow, A. L. Cooling of gases by laser radiation. Opt. Commun. 13, 68–69 (1975)

    Article  ADS  Google Scholar 

  3. Chu, S., Cohen-Tanoudji, C. N. & Phillips, W. D. Nobel lectures in physics 1997. Rev. Mod. Phys. 70, 685–741 (1998)

    Article  ADS  CAS  Google Scholar 

  4. Djeu, N. & Whitney, W. T. Laser cooling by spontaneous anti-Stokes scattering. Phys. Rev. Lett. 46, 236–239 (1981)

    Article  ADS  Google Scholar 

  5. Zander, C. & Drexhage, K. H. in Advances in Photochemistry Vol. 20 (eds Neckers, D. C., Volman, D. H. & von Bünau, G.) 59–78 (Wiley, 1995)

    Google Scholar 

  6. Epstein, R. I., Buchwald, M., Edwards, B., Gosnell, T. & Mungan, C. Observation of laser induced fluorescent cooling of a solid. Nature 377, 500–503 (1995)

    Article  ADS  CAS  Google Scholar 

  7. Hoyt, C. W. et al. Advances in laser cooling of thulium-doped glass. J. Opt. Soc. Am. B 20, 1066–1074 (2003)

    Article  ADS  CAS  Google Scholar 

  8. Thiede, J., Distel, J., Greenfield, S. R. & Epstein, R. I. Cooling to 208 K by optical refrigeration. Appl. Phys. Lett. 86, 154107 (2005)

    Article  ADS  Google Scholar 

  9. Sheik-Bahae, M. & Epstein, R. I. Optical refrigeration. Nature Photon. 12, 693–699 (2007)

    Article  ADS  Google Scholar 

  10. Berman, P. R. & Stenholm, S. Heating or cooling using collisionally aided fluorescence. Opt. Commun. 24, 155–157 (1978)

    Article  ADS  CAS  Google Scholar 

  11. Giacobino, E., Tawil, M., Berman, P. R., Redi, O. & Stroke, H. H. Production of “hot” excited-state atoms in collisionally aided radiative transitions. Phys. Rev. A 28, 2555–2557 (1983)

    Article  ADS  CAS  Google Scholar 

  12. Debenedetti, P. G. & Stanley, H. E. Supercooled and glassy water. Phys. Today 56, 40–46 (2003)

    Article  CAS  Google Scholar 

  13. Koop, T., Luo, B., Tsias, A. & Peter, T. Water activity as the determinant for homogeneous ice nucleation in aqueous solutions. Nature 406, 611–614 (2000)

    Article  ADS  CAS  Google Scholar 

  14. Adams, C. S. & Riis, E. Laser cooling and trapping of neutral atoms. Prog. Quantum Electron. 21, 1–79 (1997)

    Article  ADS  CAS  Google Scholar 

  15. Cohen-Tannoudji, C., Dupont-Roc, J. & Grynberg, G. Atom-Photon Interactions – Basic Processes and Applications 490–514 (Wiley, 1992)

    Google Scholar 

  16. Schuller, F. & Behmenburg, W. Perturbation of spectral lines by atomic interactions. Phys. Rep. 12, 273–334 (1974)

    Article  ADS  Google Scholar 

  17. Yeh, S. & Berman, P. R. Theory of collisionally aided radiative excitation. Phys. Rev. A 19, 1106–1116 (1979)

    Article  ADS  Google Scholar 

  18. Hedges, R. E. M., Drummond, D. L. & Gallagher, A. Extreme-wing line broadening and Cs-inert-gas potentials. Phys. Rev. A 6, 1519–1544 (1972)

    Article  ADS  CAS  Google Scholar 

  19. Speller, E., Staudenmayer, B. & Kempter, V. Quenching cross sections for alkali-inert gas collisions. Z. Phys. A 291, 311–318 (1979)

    Article  ADS  CAS  Google Scholar 

  20. Vogl, U. & Weitz, M. Spectroscopy of atomic rubidium at 500-bar buffer gas pressure: approaching the thermal equilibrium of dressed atom-light states. Phys. Rev. A 78, 011401 (2008)

    Article  ADS  Google Scholar 

  21. Eastham, P. R. & Littlewood, P. B. Bose condensation of cavity polaritons beyond the linear regime: the thermal equilibrium of a model microcavity. Phys. Rev. B 64, 235101 (2001)

    Article  ADS  Google Scholar 

  22. Deng, H., Weihs, G., Santori, C., Bloch, J. & Yamamoto, Y. Condensation of semiconductor microcavity exciton polaritons. Science 298, 199–202 (2002)

    Article  ADS  CAS  Google Scholar 

  23. Bolkart, C., Weiss, R., Rostohar, D. & Weitz, M. Coherent and BCS-type quantum states of dark polaritons. Laser Phys. 15, 3–6 (2005)

    Google Scholar 

  24. Whinnery, J. Laser measurement of optical absorption in liquids. Acc. Chem. Res. 7, 225–231 (1974)

    Article  CAS  Google Scholar 

  25. Jackson, W. B., Amer, N. M., Boccara, A. C. & Fournier, D. Photothermal deflection spectroscopy and detection. Appl. Opt. 20, 1333–1344 (1981)

    Article  ADS  CAS  Google Scholar 

  26. Spear, J. D., Russo, R. E. & Silva, R. J. Collinear photothermal deflection spectroscopy with light scattering samples. Appl. Opt. 29, 4225–4234 (1990)

    Article  ADS  CAS  Google Scholar 

  27. Born, M. & Wolf, E. Principles of Optics 7th edn 89–115 (Pergamon, 1999)

    Book  Google Scholar 

  28. Rosenbaum, B. M., Oshen, S. & Thodos, G. Thermal conductivity of argon in the dense gaseous and liquid regions. J. Chem. Phys. 44, 2831–2838 (1966)

    Article  ADS  CAS  Google Scholar 

  29. Tournier, J.-M. P. & El-Genk, M. S. Properties of noble gases and binary mixtures for closed Brayton cycle applications. Energy Convers. Manage. 49, 469–492 (2008)

    Article  CAS  Google Scholar 

  30. Pascale, J. & Vandeplanque, J. Excited molecular terms of the alkali-rare gas atom pairs. J. Chem. Phys. 60, 2278–2289 (1974)

    Article  ADS  CAS  Google Scholar 

Download references


We thank J. Nipper for experimental contributions during the early phase of this project. Financial support from the Deutsche Forschungsgemeinschaft within the focused research unit FOR557 is acknowledged.

Author information

Authors and Affiliations


Corresponding author

Correspondence to Martin Weitz.

PowerPoint slides

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Vogl, U., Weitz, M. Laser cooling by collisional redistribution of radiation. Nature 461, 70–73 (2009).

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI:

This article is cited by


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing