Measurements of cross polarization in negative index metamaterials

The most usual form of left handed or negative refractive index metamaterial employs planar metallic resonant structures to produce simultaneously negative electric permittivity and magnetic permeability in a microwave frequency band. These structures are similar to planar twist polarizers, which can be used to produce signal rotation and circular polarization. Because it is not possible to measure cross polarization in the guided wave chambers which are widely used with negative index metamaterials, polarization rotation has not been previously investigated. We have now performed free space measurements in an anechoic chamber and characterized the effects of negative index metamaterials on signal rotation. We have measured up to 25 degrees of polarization rotation through a negative index prism of 4 cm average thickness. We have found that polarization conversion is a significant loss mechanism which has been neglected. We also consider the importance of symmetry and prism angle geometry on this conversion loss.