Graphene circular polarization analyzer based on unidirectional excitation of plasmons

In this paper we propose a method of unidirectional excitation of graphene plasmons via metal nanoantenna arrays and reveal its application in a circular polarization analyzer. For nanoantenna pairs with orthogonal orientations, the graphene plasmons are excited through antenna resonances with the direction of propagation can be controlled by incident polarization. On the other hand, based on the spiral shape distribution of antenna arrays, a circular polarization analyzer can be obtained via the interaction of geometric phase effect of antenna arrays and the chirality carried by incident polarization. By utilizing the unidirectional excitation of plasmons, the extinction ratio of analyzer can be improved to over 10³, which is at least an order of magnitude larger than the result of antenna pairs with same orientations or antenna arrays with closed circular shape formation. The proposed analyzer may find applications in analyzing chiral molecules using different circularly polarized waves.