Method for phase extraction from atom interference fringes via orthogonal subspace projection

We propose a method for extracting the phase from atom interference fringes based on orthogonal subspace projection. By projecting the shear interference fringes from an atom interferometer into an orthogonal subspace, this method characterizes and removes the atomic ensemble envelope, thereby isolating the interference phase information. We systematically investigate the phase extraction accuracy of this method under various conditions, including different atomic ensemble envelope shapes and fringe contrasts, and apply it to analyze experimental data from two practical atom interferometers. The study demonstrates that, compared to the conventional direct model fitting method, our approach more accurately extracts the interference phase under conditions involving nonideal and dynamically varying atomic ensemble envelopes as well as low-contrast fringes, thereby improving the accuracy and robustness of the atom interferometer. This makes it particularly valuable for application-oriented atom shear interferometers operating in complex environments.