| A rotation-rate sensor was developed using atom interferometry and the Sagnac effect for matter waves. This device has a short-term sensitivity of 6 x 10-10 rad/sec for a 1 second integration time, which is the best publicly reported value to date. It has high intrinsic accuracy because it relies on interactions between atoms and laser light which is stabilized to an atomic transition. Long-term stability is promising and characterization is currently underway. Potential applications include inertial navigation, geophysical studies, and general relativity tests such as verification of the Lense-Thirring and geodetic effects.; The principle of operation is as follows: A thermal cesium atomic beam crosses three laser interaction regions where two-photon stimulated Raman transitions between cesium ground states transfer momentum to atoms and divide, deflect, and recombine the atomic wavepackets. Rotation induces a phase shift between the two possible trajectories and causes a change in the detected number of atoms with a particular internal state. Counterpropagating atomic beams form two interferometers using shared lasers for common mode rejection, and the rotation phase shifts have opposite sign since the phase shift is proportional to the vector velocity of the atoms. Therefore, subtracting or adding the interferometer signals discriminates between rotation and transverse acceleration summed with laser arbitrary phase. Furthermore, in the inertial reference frame of the atoms, rotations Doppler-shift the Raman lasers. Adding Raman frequency shifts to cancel these Doppler-shifts allows operation at an effective zero rotation rate, improving sensitivity and bandwidth. Modulating these frequency shifts facilitates sensitive lock-in detection readout techniques. |
