  The theoretical work of V.B. Braginsky predicted that radiation pressure can
couple the mechanical, mirror-eigenmodes of a Fabry-Perot resonator to it's
optical modes, leading to a parametric oscillation instability. This regime is
characterized by regenerative mechanical oscillation of the mechanical mirror
eigenmodes. We have recently observed the excitation of mechanical modes in an
ultra-high-Q optical microcavity. Here, we present a detailed experimental
analysis of this effect and demonstrate that radiation pressure is the
excitation mechanism of the observed mechanical oscillations.
