Finesse and mirror speed measurement for a suspended Fabry-Perot cavity   using the ringing effect
  We here present an investigation of the ringing effect observed on the VIRGO mode-cleaner prototype MC30. The results of a numerical calculation show how a simple empirical formula can determine the cavity expansion rate from the oscillatory behavior. We also show how the simulation output can be adjusted to estimate the finesse value of the suspended cavity. 
Luca Matone, Matteo Barsuglia, Francois Bondu, Fabien Cavalier,   Henrich Heitmann, Nary Man