A study of optical instabilities for advanced gravitational-wave detectors

[Truncated abstract] This thesis reports the experimental observations of radiation pressure induced optical instabilities in a 80 m suspended high optical power cavity. These instabilities have the potential to disrupt the operation of the next generation gravitational wave detectors. This thesis provides the theoretical development, as well as experimental results and solutions to two such optical instabilities. The rst experiment describes and presents results on the angular optical instability e ect, where, depending on several parameters, the optical spring e ect could disrupt the performance of gravitational wave interferometers. The second experiment presents two potential solutions for parametric instability, a known threat to high power Fabry-P erot optical cavities. In the angular optical instability experiment presented in this thesis, it was found that the magnitude of the negative optical spring constant per unit power is a few N m=W as the result of optical torsional sti ness in the yaw mode of the suspended mirror south arm Fabry-P erot cavity at AIGO. These results are shown to be consistent with the theory, reviewed also in this theory, of the optical torque e ect as described by Sidles and Sigg in their paper published in 2006 [56]. The parametric instability experiment described in this thesis provides a preliminary solution to the opto-acoustic parametric interactions as they arise in high power, suspended Fabry-P erot cavities. This experiment demonstrated the suppression of an excited high order in the south arm Fabry-P erot cavity at AIGO, by injecting a low power, anti-phase TEM01 mode, as part of an optical feedback loop, into the cavity to destructively interfere with the excited cavity mode. Although preliminary, the results of this experiment provide a stepping stone to nding a solution using an optical feedback loop, to suppress parametric instability in advanced gravitational wave detectors...