10 Mai – Thesis defense - Grégoire Lefèvre
14 h Amphi / Institut d'Optique d'Aquitaine (Talence)
Development of a cavity enhanced atom interferometer for the MIGA project.
After few decades of development, atom interferometry has become an extremely powerful tool for measuring inertial effects such as accelerations and rotations. These techniques are now considered for future gravitational wave detectors to push the limits of the state of the art of optical detectors. In this context, the MIGA (Matter-Wave Laser Interferometer Gravitation Antenna) instrument will couple atom and optical interferometry to study low frequency perturbations of the gravitational field. It will consist of a set of 3 atom interferometers simultaneously interrogated by the resonant field of two 150 m optical cavities using a set of high order π/2- π- π/2 Bragg pulses. Differential gradiometric measurements will provide strong immunity to seismic and Newtonian noise that is limiting at frequencies of the order of the Hz for optical terrestrial detectors such as LIGO and Virgo. A preliminary experiment is being developed at LP2N in Talence (France), where an interferometer is interrogated by two 80 cm long optival cavities 80 cm. To be able to have a sufficient beam size resonating inside the 80cm long cavities and efficiently interrogate the atoms, we use a marginally stable cavity geometry consisting of two plane mirrors located at the focal length of a biconvex lens where a waist of several mm can be obtained.