Atom interferometry with phase-masked optical fields

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2002.Includes bibliographical references (p. 179-180).We have investigated the use of two-photon induced spin excitation for applications to atom interferometry for lithography and rotation sensing. Our efforts have been grouped into two parts: theoretical study of schemes for nanolithography, and experimental investigation of novel schemes for rotation sensing. For lithography, we have concentrated on designing and studying theoretical models that would allow the creation of two-dimensional lithographic patterns with nanometer scale features. Specifically, We have developed a theoretical model for realizing a two-dimensional interferometer capable of producing periodic structures with a feature size of less than 10 nm. Fundamentally, this process uses the two-photon induced spin excitation for splitting atomic waves. We first extended this model to achieve a large degree of splitting via use of multiple pulses, and then showed how the process can be generalized to two orthogonal dimensions with independent controls. We have also designed a scheme for producing arbitrary two-dimensional features using atom interferometry. This process makes use of a phase mask imprinted on a laser pulse, guiding of atomic waves, and atom interferometry in order to produce any desired pattern, with features that can also be only a few nm's in size. For rotation sensing, we have realized experimentally a novel scheme that opens up a new way of controlling the interferometer contour. It may prove to be very robust for practical applications such as gravity gradiometry as well.(cont.) This process uses a single optical zone with two counter-propagating optical frequencies. The zone can be compartmented into small sections, and the optical phase of each section can be switched between 0 and n in a variable pattern. We have shown via simulations that a wide range of split-wave contours can be realized, including multiple loops of varying areas. Experimentally, we have demonstrated a preliminary version of this scheme. We have demonstrated the atomic interference via scanning the phase of a part of the optical beam. When realized in conjunction with trapped atoms, this scheme is expected to yield a rotation sensing ability that is comparable to the three-zone Raman interferometer. However, it has the advantage of being robust against angular misalignment and differential light shifts. Furthermore, it opens up the possibility of realizing atomic interferometry with dynamically tunable contours.by Ying Tan.Ph.D