Speaker
Julia Casanueva Diaz
Description
The most promising gravitational waves (GW) detectors to date are kilometric Michelson interferometers with additional recycling Fabry-Perot cavities to enhance their sensitivity, and all the mirrors suspended. The second generation aims for the first direct detection of GW, and in order to do so, a sensitivity improvement of one order of magnitude is foreseen (~$10^{-19}$ m rms). Several upgrades are underway, and among them the addition of a new optical cavity, which introduces new couplings, increasing the complexity to control the instrument.
A new technique, based on the use of auxiliary lasers, has been developed in order to bring the interferometer to its working point (all the cavities on their resonance) in an adiabatic way. Not only simulations are required, but also experimental tests that can be made in facilities like CALVA, located at Laboratoire de l'Accelerateur Lineaire in Orsay, and which consists of two coupled suspended cavities of 50 and 5m respectively, similar to the ones in Advanced Virgo (AdV).
We will review all the details of the implementation of this technique in AdV, being the propagation of a stable laser through a 3-km optical fiber one of the most problematic. A new technique of active phase noise cancellation based on the use of Electro Optical Modulators has been developed, and a first prototype has been successfully tested.
