Polarization conversion with a photonic crystal slab

We show that a photonic crystal can enable efficient polarization conversion. Two mechanisms are identified. The first relies on the anisotropy of the bulk properties of the metamaterial and is mediated by interferences. The second mechanism is dueto the resonant excitation of leaky surface waves at the interface of the photonic crystal. The latter is analogous to the polarization conversion by escitation of surface plasmons on a metallic grating. This is another example of the possibility of mimicking plasmonics with photonic crystals.