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

基于亚波长结构的偏振元件在光学中的应用越来越广泛。一个例子是径向偏振光的产生，其可用于显微镜以产生特别小的旋转对称焦点。然而，除了偏振之外，这些因素通常还会影响入射光场的相位。因此，同时测量光场的偏振态和相位是一项重要的任务。到目前为止，只能通过偏振的斯托克斯测量和相位的干涉测量来分别确定相位和偏振。然而，当在干涉仪中使用具有空间变化的偏振的光场来确定相位时，干涉图中存在物体和参考光束的偏振相互垂直的区域，其中存在对比度消失的区域。测量只能在对比度较好的区域进行，这些区域之间的方向并不明确。因此，对于一般的偏振光，用标准方法不可能确定整个区域的相位。为了克服这些问题，提出了一种新的测量方法，它可以在一个测量过程中同时确定光的相位和一般的、即空间可变的椭圆偏振态。解决方案在于通过增加参考偏振的变化来扩展众所周知的相移干涉测量方法。通过这种偏振和相移干涉测量，可以获得关于物波的附加信息。

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.