Flat Chiral Irises in a Square Waveguide and Displays of “Optical Activity”

On the example of a square waveguide with a tetraslot iris, possessing rotational symmetry of fourth order and additional simple elements, the spatial spectrum of modes excited in reflected and transmitted fields is analyzed. The reasons of appearance of cross-polarized field behind a waveguide object are found and investigated. They allow extending our conclusions on the “optically active” metamaterials created on the basis of periodically located flat chiral elements.