Novel atom interferometry techniques for a cold-atom gyroscope of large Sagnac area

This thesis describes the implementation of new atom interferometry techniques to improve the stability and accuracy of a cold-atom gyroscope located at the SYRTE laboratory. Stimulated Raman transitions are used to split and recombine the atomic waves. A sequence of four light pulses generates an interferometer with a Sagnac area of 11 cm². The implementation of an interleaved interrogation scheme is presented, where three atomic clouds are interrogated simultaneously in an atom interferometer featuring a sampling rate of 3.75 Hz and an interrogation time of 801 ms. With this scheme a short-term sensitivity of 30 nrad·s^–1/Hz^½ has been demonstrated. We then present measurements of dynamic rotation rates in a so far unexplored range for a cold atom sensor. An important bias of the sensor originates from a coupling between a relative misalignment of the mirrors which retro-reflect the Raman beams and the trajectory of the atom. A technique is introduced to reduce this bias at the level of 1 nrad·s^-1 and to achieve a long-term stability of 0.3 nrad·s^-1 which represents the state of the art for atomic gyroscopes. The manuscript then describes the first characterization of the scale factor of the gyroscope using different techniques. In particular, the implementation of a rotation stage below the sensor enables us to vary the projection of the Erath rotation rate vector onto the interferometer area and therefore to modulate the rotation phase shift. The implementation of the techniques presented in this thesis pave paving the way to a test of the Sagnac effect for matter waves with a relative accuracy level below 100 parts per million.

atom interferometry, inertial sensor, cold atom, gyroscope, Sagnac effect, stimulated Raman transitions

Full document : https://tel.archives-ouvertes.fr/tel-02931881