Self-alignment of a compact large-area atomic Sagnac interferometer

We report on the realization of a compact atomic Mach–Zehndertype Sagnac interferometer of 13.7 cm length, which covers an area of 19mm2 previously reported only for large thermal beam interferometers. According to Sagnac’s formula, which holds for both light and atoms, the sensitivity for rotation rates increases linearly with the area enclosed by the interferometer. The use of cold atoms instead of thermal atoms enables miniaturization of Sagnac interferometers without sacrificing large areas. In comparison with thermal beams, slow atoms offer better matching of the initial beam velocity and the velocity with which the matter waves separate. In our case, the area is spanned by a cold atomic beam of 2.79m s−1, which is split, deflected and combined by driving a Raman transition between the two hyperfine ground states of 87Rb in three spatially separated light zones. The use of cold atoms requires a precise angular alignment and high wave front quality of the three independent light zones over the cloud envelope. We present a procedure for mutually aligning the beam splitters at the microradian level by making use of the atom interferometer itself in different configurations. With this method, we currently achieve a sensitivity of 6.1× 10−7 rad s−1Hz. 1 Author to whom any correspondence should be addressed. New Journal of Physics 14 (2012) 015002 1367-2630/12/015002+14$33.00 © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft