Spontaneous emission in paired graphene plasmonic waveguide structures

The coupling between a single emitter and surface plasmons in paired graphene layers and in paired graphene ribbons are studied. For paired graphene layers, the coupling between surface plasmons in graphene layers is strong at low photon energy and small gap between layers, which results in strong enhancement of the emitter's emission. The excitation efficiency of surface plasmons by a single emitter can be increased to nearly 1 in paired graphene layers. With the increase of the photon energy, emitter's emission in paired layers is weakened and could be lower than that in graphene monolayer. For graphene paired ribbons, numerical simulations show similar properties of emission enhancement and high excitation efficiency of surface plasmons. The emission enhancement and the excitation efficiency of surface plasmons can be improved by narrowing the ribbon width.