Simultaneous measurement of phase and spatially variant elliptical polarization of light fields

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Polarization elements which are based on subwavelength structures increasingly find applications in optics. An example is the generation of radially polarized light which may be used in microscopy to create particularly small rotationally symmetric foci. Aside from the polarization, however, such elements in general affect the phase of the incident light field. Therefore, the simultaneous measurement of the polarization state and the phase of the light field is an important task. Up to now, phase and polarization can only be separately determined, via Stokes measurements for the polarization and interferometric measurements for the phase. When a light field with a spatially varying polarization is used in an interferometer to determine the phase, however, regions in the interferogram with vanishing contrast exist where the polarizations of object and reference beam are orthogonal. The measurement can only be performed in the regions with good contrast, and the orientation of these regions to each other is not clear. For generally polarized light, a determination of the phase for the whole area is therefore not possible with standard methods. To overcome these problems, a novel measurement method is proposed which enables the simultaneous determination of the phase and a general, i. e. spatially variant elliptical polarization state of light within one single measurement process. The solution consists in extending the well known procedure of phase shifting interferometry by an additional variation of the reference polarization. By means of such a polarization and phase shifting interferometry the additional information about the object wave can be gained.