Speaker
Description
Increasing the circulating power in gravitational-wave detectors to the megawatt level is essential for their proposed sensitivity, but this is critically limited by optomechanical parametric instabilities. Current mitigation strategies are projected to be ineffective against instabilities when circulating power reaches megawatt. Optical feedback offers a novel independent paradigm to mitigate parametric instability. In this Letter, we report the first demonstration of optical feedback control in a full-scale gravitational wave detector. We successfully suppress an unstable mode at $10.428\,$kHz, reducing the parametric gain from $R\approx 2$ to $R<0.02$. This work validates optical feedback control as an effective mitigation scheme for kilometer-scale interferometric gravitational-wave detectors, providing an effective strategy to allow detectors to reach the megawatt level.