  The highly unidirectional excitation of graphene plasmons (GPs) through
near-field interference of orthogonally polarized dipoles is investigated. The
preferred excitation direction of GPs by a single circularly polarized dipole
can be simply understood with the angular momentum conservation law. Moreover,
the propagation direction of GPs can be switched not only by changing the phase
difference between dipoles, but also by placing the z-polarized dipole to its
image position, whereas the handedness of the background field remains the
same. The unidirectional excitation of GPs can be extended directly into arc
graphene surface as well. Furthermore, our proposal on directional generation
of GPs can be realized in a semiconductor nanowire/graphene system, where a
semiconductor nanowire can mimic the circularly polarized dipole when
illuminated by two orthogonally polarized plane waves.
