Etude du couplage optomecanique dans une cavite de grande finesse.   Observation du mouvement Brownien d'un miroir
  The topic of this thesis is the theoretical analysis of the optomechanical coupling effects in a high-finesse optical cavity, and the experimental realization of such a device. Radiation pressure exerted by light limits the sensitivity of high precision optical measurements. In particular, the sensitivity of interferometric measurements of gravitational wave is limited by the so called standard quantum limit. cavity with a movable mirror. The internal field stored in such cavity can be orders of magnitude greater than the input field, and it's radiation pressure force can change the physical length of the cavity. In turn, any change in the mirror's position changes the phase of the out put field. This optomechanical coupling leads to an intensity-dependent phase shift for the light equivalent to an optical Kerr effect. Such a device can then be used for squeezing generation or quantum nondemolition measurements. In our experiment, we send a laser beam in to a high-finesse optical cavity with a movable mirror coated on a high Q-factor mechanical resonator. Quantum effects of radiation pressure become therefore, at low temperature, experimentally observable. However, we've shown that the phase of the reflected field is very sensitive to small mirror displacements, which indicate other possible applications of this type of device like high precision displacements measurements. We've been able to observe the Brownian motion of the moving mirror. We've also used an auxiliary intensity modulated laser beam to optically excite the acoustic modes. We've finally obtained a sensitivity of 2x10^(-19) m/sqrt(Hz), in agreement with theoretical prediction. 
Yassine Hadjar