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Mach-Zehnder-Interferometer (PPSI)

A Mach-Zehnder interferometer has been developed for the simultaneous and spatially resolved measurement of phase and polarization in one measurement procedure. This was achieved by introducing a new method (s. g. PPSI: ”polarisation and phase shifting interferometry”) – where a set of algorithms similar to the well established ones used in PSI with an additional variation of a reference polarization is applied.

Principle

The measurement setup is a folded Mach-Zehnder interferometer. The variation of the polarisation and the phase of the reference beam is done by two rotatable polarisation elements (HWP and QWP) and a movable mirror (M2), respectively. An almost normal incidence on the mirrors is necessary to suppress the influence of the mirror reflections on the polarization states, as the Fresnel coefficients indicate. As a beam splitter (BS), a Wollaston prism is used, that allows to adjust the visibility of the interferograms by controlling the intensity ratio between object and reference wave. To conserve any polarization patterns present in the incident beams a specially designed phase grating is used as a beam combiner (BC).