1. CNRS LKB – Task T1 Current status of the experiment on optomechanical coupling Sensitivity: 5.10  20 m.Hz  1/2   New high-finesse, high-power cavity (F  200 000) Objectives: observation of quantum noises and quantum limits Expected sensitivity  10  21 m.Hz  1/2

2. CNRS LKB – Task T1 Experiment on thermal noise at low frequency Current status: development of the laser source Intensity stabilization at the shot noise level at low frequency Objectives: sensitivity  10  20 m.Hz  ½ at frequency > 100 Hz Theoretical study of thermoelastic noises Frequency dependence due to non-adiabatic conditions

3. Task T2 – Measurement of photo-elastic noise Photo-thermal noise is due to the conduction inside mirrors and coatings of the heat induced by photon absorption. It can be tested using the photo-elastic effect induced by an intensity modulation of the light entering a Fabry-Perot cavity Objectives :- observation of photo-elastic effects - dependence with temperature down to tenths of K - test of low optical loss coatings

4. Task T2 – Measurement of photo-elastic noise Measurement of photo-thermal effect induced by an intensity-modulated light beam Experiment:M. De Rosa, L. Conti, M. Cerdonio, M. Pinard, F. Marin, Phys. Rev. Lett. 89, 237402 (2002) Theory:M. Cerdonio, L. Conti, A. Heidmann, M. Pinard, Phys. Rev. D 63, 082003 (2001)

5. CNRS LKB – Task T2 Test and set-up of high-finesse cryogenic cavities Cavities with low-loss coatings suitable for cryogenic applications Theoretical study of photo-elastic noise Theoretical investigation on light absorption effects of coatings at low temperature Measurement of photo-thermal effect at low temperature Using the experiment on opto- mechanical coupling with a cryogenic cavity and an intensity- modulated laser beam

6. CNRS LKB – Task T3 Developments of Fabry-Perot cavities with wide area read-out -Folded FP cavity (collaboration with LENS) Theoretical calculation of selective read-out for dual-sphere detectors with several optical sensors -Concave-convex cavities Tests of thermal noise reduction and signal-to- noise enhancement with wide area cavities Direct measurement of thermal noise background Dependence with the effective area