  We investigated the opto-mechanical properties of a Fabry-Perot cavity with a
mirror mounted on a spring. Such a structure allows the cavity length to change
elastically under the effect of light induced forces. This opto-mechanical
coupling is exploited to control the amplitude of mechanical fluctuation of the
mirror. We present a model developed in the classical limit and discuss data
obtained in the particular case for which photo-thermal forces are dominant.
