L'interféromètre Virgo :<br />propriétés optiques, stabilisation en fréquence du laser

An interferometer with suspended mirrors converts gravitational waves, space-time metric perturbations, in photon time of flight variations between two inertial masses at rest.<br />I describe the laser frequency stabilization setup to measure these time of flight variations. The obtained relative stability, in-loop, is 1e-21 on a 100 ms timescale. I show that the specifications are met. I study the stability conditions for a system with multiple servo loops.<br />The Virgo optical resonant cavities are the elementary bricks to convert a gravitational wave. I study the properties of a Fabry-Perot cavity. I show how the properties can be measured in situ with the transfer function used to lock the cavity. Fabry-Perot cavities are reference oscillators. I list the possible perturbations that perturb the phase stability.