Resolved-sideband cooling of a micromechanical oscillator

In atomic laser cooling, preparation of the motional quantum ground state has been achieved using resolved-sideband cooling of trapped ions. Here, we report the first demonstration of resolved-sideband cooling of a mesoscopic mechanical oscillator, a key step towards ground-state cooling as quantum back-action is sufficiently suppressed in this scheme. A laser drives the first lower sideband of an optical microcavity resonance, the decay rate of which is twenty times smaller than the eigenfrequency of the associated mechanical oscillator. Cooling rates above 1.5 MHz are attained, three orders of magnitude higher than the intrinsic dissipation rate of the mechanical device that is independently monitored at the 10(-18) m/root Hz level. Direct spectroscopy of the motional sidebands of the cooling laser confirms the expected suppression of motional increasing processes during cooling. Moreover, using two-mode pumping, this regime could enable motion measurement beyond the standard quantum limit and the concomitant generation of nonclassical states of motion.