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, excitation of Stokes optical modes occurs in 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 pumps 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.