Directional Excitation of Plasmons on Dual- Functional Graphene-Coated Dielectric Gratings

We propose a scheme to achieve the directional excitation of plasmons based on dual-functional graphene-coated dielectric gratings. In such a scheme, two identical grating structures are incorporated to achieve directional plasmons excitation, and each grating structure could individually serve as the coupler from vertical incident light to graphene plasmons or Bragg reflector for the in-plane incident plasmons wave. By letting the plasmons excitation wavelength of coupler equal to the Bragg wavelength of plasmons reflector and selectively illuminating one of the two grating structures, the excitation of plasmons along only one direction can be achieved. Furthermore, the direction of plasmons excitation can be reversed via simply shifting the region of illumination from one grating structure to the other. The proposed scheme may provide new possibilities in the directional excitation of graphene plasmons through the launching procedure.