Parametric oscillatory instability in gravitational wave laser detectors

The nonlinear effect of parametric oscillatory instability in the gravitational wave laser detector (antenna) is considered as a factor that considerably reduces the sensitivity of the device. It is shown that in an antenna with a circulating power above a certain threshold value there occurs excitation of Stokes optical modes in the Fabry-Perot resonators and of test mass elastic modes. Parametric oscillatory instability in gravitational wave interferometers of the second (LIGO, Virgo, LCGT, GEO-600) and third (ET - Einstein Telescope) generation with different types of pump is examined. The effect discussed has been observed not only in gravitational wave laser interferometers, but also many times in other opto-mechanical systems. All current methods for suppressing parametric oscillatory instability in gravitational wave interferometers are also discussed, both passive and active.