Optical metrology for massive detectors of gravitational waves

The high level reached in the stability of laser sources and in the quality of optical components makes interferometric metrology appealing to those involved in the search for detection of gravitational waves (GWs). In this paper we present a readout for massive detectors of GWs, based on laser interferometry with high finesse Fabry–Pérot cavities, and describe the frequency stability of the laser source. The achievable sensitivity at the quantum limit level inherent to this technique requires a careful design, in order to reduce other sources of extra noise. In particular, we focus on the local effects of thermal and radiation pressure fluctuations and present an optical configuration that can reduce these effects below the quantum limit level.