For more than three decades, dynamical backaction in the form of radiation pressure has been predicted to give rise to intricate coupled dynamics of the optical modes of a high-finesse cavity and the mechanical modes of its boundaries . In particular, if the mechanical oscillation period is comparable to the cavity’s photon lifetime, and the cavity is pumped with a red-detuned laser, the Brownian motion of the mechanical mode can be reduced, corresponding to an effective temperature reduction or cooling. Here we report on the first the experimental observation of this phenomenon using very high-finesse toroidal silica microresonators . These structures (Fig. 1A) possess whispering gallery type optical modes (with photon lifetimes up to 500 ns) while simultaneously exhibiting micro-mechanical resonances in the radio-frequency domain. We study the interaction of the intracavity light with the ~60 MHz radial breathing mode of the cavity, depicted in the inset of Fig. 1A.
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