Self-cooling of a micromirror by radiation pressure

Author(s): S. Gigan, M. Aspelmeyer, D. Bäuerle, K. C. Schwab, J. B. Hertzberg, G. Langer, F. Blaser, M. Paternostro, H. R. Böhm, A. Zeilinger

Journal: Nature

Volume: 444

Page(s): 67-70

Year: 2006

DOI Number: 10.1038/nature05273

Link: Link to publication

Abstract:

Cooling of mechanical resonators is currently a popular topic in

many fields of physics including ultra-high precision measurements

1, detection of gravitational waves2,3 and the study of the

transition between classical and quantum behaviour of a mechanical

system4–6. Here we report the observation of self-cooling of a

micromirror by radiation pressure inside a high-finesse optical

cavity. In essence, changes in intensity in a detuned cavity, as

caused by the thermal vibration of the mirror, provide the mechanism

for entropy flow from the mirror’s oscillatory motion to the

low-entropy cavity field2. The crucial coupling between radiation

and mechanical motion was made possible by producing freestanding

micromirrors of low mass (m<400 ng), high reflectance

(more than 99.6%) and high mechanical quality (Q<10,000). We

observe cooling of the mechanical oscillator by a factor of more

than 30; that is, from room temperature to below 10 K. In addition

to purely photothermal effects7 we identify radiation pressure as a

relevant mechanism responsible for the cooling. In contrast with

earlier experiments, our technique does not need any active

feedback8–10. We expect that improvements of our method will

permit cooling ratios beyond 1,000 and will thus possibly enable

cooling all the way down to the quantum mechanical ground state

of the micromirror.

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