Activities for gravitational interferometers
The Virgo group at LKB is part of the “Optomechanics and Quantum Measurement” team in this laboratory. The group is investigating the possibility of using frequency-dependent squeezing to improve the sensitivity of Advanced Virgo. Tests will be carried out on the 50 m cavity of the CALVA platform at the Linear Accelerator Laboratory. Frequency-dependent squeezing would reduce quantum noise in both the low-frequency range (where the sensitivity of Advanced Virgo will be limited by the radiation pressure) and in the high-frequency range (where the shot noise of the photons in the laser beam dominates).
In addition, the LKB group studies the classical effects of radiation pressure in gravitational wave detectors and develops control strategies to attenuate it. For example, the use of high laser power creates a coupling between the internal vibration modes of the mirror substrates and the transverse optical modes of the mileage cavities. The occurrence of dynamic instabilities is predicted under certain conditions, a phenomenon that the LKB group has highlighted and studied in tabletop experiments. Such instabilities could prevent advanced gravity-wave interferometric detectors from using the full power of their lasers.