Realizing polarization conversion and unidirectional transmission by using a uniaxial crystal plate

We show that polarization states of electromagnetic waves can be manipulated easily using a single thin uniaxial crystal plate. By performing a rotational transformation of the coordinates and controlling the thickness of the plate, we can achieve a complete polarization conversion between TE wave and TM wave in a spectral band. We show that the off-diagonal element of the permittivity is the key for polarization conversion. Our analysis can explain clearly the results found in experiments with metamaterials. Finally, we propose a simple device to realize unidirectional transmission based on polarization conversion and excitation of surface plasmon polaritons.