(a) Schematic optomechanical setup. An optical cavity is formed by two parallel mirrors (blue), one of which is attached to a cantilever. Laser light entering the cavity (green) induces radiation pressure that moves the cantilever, which in turn alters the optical mode frequency relative to the laser frequency. (b) Plot of radiation pressure force vs position. As the mirror oscillates, the system moves up and down the slope of the resonance, leading to damping of the mirror fluctuations. (c) Periodic motion of the mirror produces sidebands at ±ωM. In the quantum picture of cooling, Raman-scattered laser photons see a density of states that is changed by the presence of the cavity. An asymmetry in which the density of states is higher for the “anti-Stokes” sideband ωL + ωM leads to net cooling of the cantilever.