Testing the suppression of opto-acoustic parametric interactions using optical feedback control

We report an investigation designed to suppress three-mode opto-acoustic parametric interactions in advanced gravitational-wave detectors, through optical feedback control. In this paper, we present our initial results on the control of parametric instability in a high-finesse Fabry-Perot cavity using low input laser power. We show that injection of an anti-phase TEM(01) mode with appropriate power will optically interfere and suppress the excited high-order mode in the cavity within a few seconds.