  The intracavity power, and hence sensitivity, of optomechanical sensors is
commonly limited by parametric instability. Here we characterize the parametric
instability induced sensitivity degradation in a micron scale cavity
optomechanical system. Feedback via optomechanical transduction and electrical
gradient force actuation is applied to suppress the parametric instability. As
a result a 5.4 fold increase in mechanical motion transduction sensitivity is
achieved to a final value of $1.9\times 10^{-18}\rm m Hz^{-1/2}$.
