Cold atom sagnac interferometer (CASI)

Abstract

The technology of cold atom fountains and matter-wave interferometry has enabled many very sensItIve measurement methods for fundamental physics and metrology [1], but it has also found applications in fields like quantum computation [2]. We present an atomic gyroscope for the precise measurement of rotations based on optical Raman transitions for the coherent beam splitting process. Two interferometers with overlapping counter propagating atomic trajectories are used to distinguish between rotation and acceleration. Cold 87 Rb atoms are provided by two atomic sources, each of them consisting of a 2D and a subsequent 3D magneto-optical trap [3]. Using the technique of moving molasses, the atoms are loaded into the interferometry chamber with a temperature of about 8 �K and a drift velocity of 2.8 m/s. The optical cooling is realized by amplified diode laser systems and a new high power self-seeded tapered amplifier [4], [5]. The sensor operates in a so called symmetric Ramsey-Borde configuration consisting of four nl2-pulses enclosing an area of 8.6 mm 2 by the atomic trajectories. In this setup we obtain a phase resolution for rotations of 9.5 mrad over an integration time of about 300s. This corresponds to a current sensitivity of a few 10. 7 radls ( see Fig.I). Besides the reduction of the dominant noise sources, the modification of the conventional Raman beam splitting process to large momentum transfer beam splitter is an approach to increase the sensitivity by enlarging the enclosed interferometric area. The transfer of many photon momenta onto the atomic ensemble is realized via a rapid adiabatic passage in an accelerated optical lattice of two counter propagating light fields. 650 mrad@ls r--sumsig n al { rotation )