An optical readout configuration for advanced acoustic gravitational wave detectors

Advanced configurations of acoustic gravitational wave detectors, using nested masses to ob- tain a wide useful bandwidth, have a very large potential sensitivity. The main problem that must be tackled in their design and construction concerns the readout of the weak vibration signal. Optical techniques are very promising, but the schemes considered up to now are limited by the thermal and radiation pressure fluctuations induced by the small interrogation area. In this work we propose and analyze a different optical configuration which allows to overcome this problem and exploit the full sensitivity, even for the recently proposed new generation of gravitational wave detectors.