Polarization-shifting method for step interferometry

TLDR: In this article, a phase step interferometry system using polarization shifting is described, which is essentially a Mach-Zehnder interferometer in which the polarization of light travelling through one arm is orthogonal to the polarization travelling through the other arm.

Abstract: A phase step interferometry system using polarization shifting is described. The device is essentially a Mach-Zehnder interferometer in which the polarization of light travelling through one arm is orthogonal to the polarization of light travelling through the other arm. At the interferometer output we place a quarter-wave plate with its fast axis at with respect to the polarization directions and a polarizer. By rotating the polarizer, the interfering waves acquire an extra phase (of topological origin) to that expected from the calculations of optical path lengths, and thus, arbitrary phase shifts can be induced. Then, from a set of interferograms recorded while the reference phase is changed, the `dynamical' phase difference (e.g. the phase profile of an object placed in one of the interferometer arms) can be reconstructed by using techniques of phase-shifting interferometry.