In this work we combine the large per-photon optical gradient force with the sensitive feedback of a high quality factor whispering-gallery microcavity. The cavity geometry, consisting of a pair of silica disks separated by a nanoscale gap, shows extremely strong dynamical backaction, powerful enough to excite giant coherent oscillations even under heavily damped conditions (mechanical Q=4). In vacuum, the threshold for regenerative mechanical oscillation is lowered to an optical input power of only 270-nanoWatts, or roughly 1000 stored cavity photons, and efficient cooling of the mechanical motion is obtained with a temperature compression factor of 13-dB for 4-microWatts of dropped optical input power.
@article{arxiv.0905.2716,
title = {Mechanical oscillation and cooling actuated by the optical gradient force},
author = {Qiang Lin and Jessie Rosenberg and Xiaoshun Jiang and Kerry J. Vahala and Oskar Painter},
journal= {arXiv preprint arXiv:0905.2716},
year = {2013}
}