  By relying on an advanced Jones calculus we analyze the polarization
properties of light upon propagation through metamaterial slabs in a
comprehensive manner. Based on symmetry considerations, we show that all
periodic metamaterials may be divided into five different classes only. It is
shown that each class differently affects the polarization of the transmitted
light and sustains different eigenmodes. We show how to deduce these five
classes from symmetry considerations and provide a simple algorithm that can be
applied to decide by measuring transmitted intensities to which class a given
metamaterial is belonging to only.
