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Cavity cooling of a microlever


The prospect of realizing entangled quantum states between macroscopic objects and photons1 has recently stimulated interest in new laser-cooling schemes2,3. For example, laser-cooling of the vibrational modes of a mirror can be achieved by subjecting it to a radiation2 or photothermal4 pressure, actively controlled through a servo loop adjusted to oppose its brownian thermal motion within a preset frequency window. In contrast, atoms can be laser-cooled passively without such active feedback, because their random motion is intrinsically damped through their interaction with radiation5,6,7,8. Here we report direct experimental evidence for passive (or intrinsic) optical cooling of a micromechanical resonator. We exploit cavity-induced photothermal pressure to quench the brownian vibrational fluctuations of a gold-coated silicon microlever from room temperature down to an effective temperature of 18 K. Extending this method to optical-cavity-induced radiation pressure might enable the quantum limit to be attained, opening the way for experimental investigations of macroscopic quantum superposition states1 involving numbers of atoms of the order of 1014.

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Figure 1: Experimental set-up.
Figure 2: Cavity-induced cooling of the lever vibrational resonance.
Figure 3: Lever vibrational resonance frequency and shape as a function of the optical cavity tuning.


  1. Marshall, W., Simon, C., Penrose, R. & Bouwmeester, D. Toward quantum superpositions of a mirror. Phys. Rev. Lett. 91, 130401 (2003)

    Article  ADS  MathSciNet  Google Scholar 

  2. Cohadon, P. F., Heidmann, A. & Pinard, M. Cooling of a mirror by radiation pressure. Phys. Rev. Lett. 83, 3174–3177 (1999)

    Article  ADS  CAS  Google Scholar 

  3. Wilson-Rae, I., Zoller, P. & Imamoglu, A. Laser cooling of a nanomechanical resonator mode to its quantum ground state. Phys. Rev. Lett. 92, 075507 (2004)

    Article  ADS  CAS  Google Scholar 

  4. Mertz, J., Marti, O. & Mlynek, J. Regulation of a microlever responses by force feedback. Appl. Phys. Lett. 62, 2344–2346 (1993)

    Article  ADS  Google Scholar 

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

    Article  ADS  Google Scholar 

  6. Cohen-Tannoudji, C. & Phillips, W. New mechanisms for laser cooling. Phys. Today 43, 33–52 (1990)

    Article  CAS  Google Scholar 

  7. Chu, S., Hollberg, L., Bjorgholm, J. E., Cable, A. & Ashkin, A. Three-dimensional viscous confinement and cooling of atoms by resonance radiation pressure. Phys. Rev. Lett. 55, 48–51 (1985)

    Article  ADS  CAS  Google Scholar 

  8. Epstein, R. I., Buchwald, M. I., Edwards, B. C., Gosnell, T. R. & Mungan, C. E. Observation of laser-induced fluorescent cooling of a solid. Nature 377, 500–502 (1995)

    Article  ADS  CAS  Google Scholar 

  9. Braginsky, V. B. & Manukin, A. B. Measurements of Weak Forces in Physics Experiments (Chicago Univ. Press, Chicago, 1977)

    Google Scholar 

  10. Braginsky, V. B., Manukin, A. B. & Tikhonov, M. Yu. Investigation of dissipative ponderomotive effects of electromagnetic radiation. Zh. Eksp. Teor. Fiz. 58, 1549–1552 (1970); Sov. Phys. JETP 31, 829–830 (1970)

    Google Scholar 

  11. Dorsel, A., McCullen, J. D., Meystre, P., Vignes, E. & Walther, H. Optical bistability and mirror confinement induced by radiation pressure. Phys. Rev. Lett. 51, 1550–1553 (1983)

    Article  ADS  Google Scholar 

  12. Vogel, M., Mooser, C., Karrai, K. & Warburton, R. Optically tunable mechanics of microlevers. Appl. Phys. Lett. 83, 1337–1339 (2003)

    Article  ADS  CAS  Google Scholar 

  13. Sarid, D. Scanning Force Microscopy (Oxford Univ. Press, New York, 1991)

    Google Scholar 

  14. Gillespie, D. T. The mathematics of Brownian motion and Johnson noise. Am. J. Phys. 64, 225–240 (1996)

    Article  ADS  Google Scholar 

  15. Gimzewski, J. K., Gerber, Ch., Meyer, E. & Schlitter, R. R. Observation of a chemical reaction using a micromechanical sensor. Chem. Phys. Lett. 217, 589–594 (1994)

    Article  ADS  CAS  Google Scholar 

  16. Barnes, J. R., Stephenson, R. J., Welland, M. E., Gerber, Ch. & Gimzewski, J. K. Photothermal spectroscopy with femtojoule sensitivity using a micromechanical device. Nature 372, 79–81 (1994)

    Article  ADS  CAS  Google Scholar 

  17. Datskos, P. G., Lavrik, N. V. & Rajic, S. Performance of uncooled microcantilever thermal detectors. Rev. Sci. Instrum. 75, 1134–1148 (2004)

    Article  ADS  CAS  Google Scholar 

  18. Yang, J., Ono, T. & Esashi, M. Surface effects and high quality factor in ultrathin single-crystal silicon cantilever. Appl. Phys. Lett. 77, 3860–3862 (2000)

    Article  ADS  CAS  Google Scholar 

  19. Pai, A., Dhurandhar, S. V., Hello, P. & Vinet, J. Y. Radiation pressure induced instabilities in laser interferometeric detectors of gravitational waves. Eur. Phys. J. D 8, 333–346 (2000)

    Article  ADS  CAS  Google Scholar 

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We thank T. Hänsch, A. Imamoglu, R. Warburton and S. Huant for discussions. The Deutsche Forschungsgemeinschaft (DFG) funded this work.

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Correspondence to Khaled Karrai.

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Metzger, C., Karrai, K. Cavity cooling of a microlever. Nature 432, 1002–1005 (2004).

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