In-plane reflection phase engineering of graphene plasmons realized by electronic boundary design at the nanoscale

Understanding and controlling the reflection phase picked up by graphene plasmons (GPs) upon scattering at graphene boundaries is a prerequisite for designing the GP propagation and the resonance properties of GPs in nanostructures. However, an efficient method that could continuously change the reflection phase of GPs in a wide range is still lacking. Here, we demonstrate that the reflection phase of GPs can be effectively controlled by electronic boundary design. Specifically, a Fabry–Pérot (F–P) cavity is constructed by two electronic boundaries and then acts as an equivalent reflection boundary. Theoretical results show that the reflection phase of GPs could continuously vary in a wide range, almost 2π, by simply changing the graphene Fermi energy and the width of the F–P cavity. Furthermore, the evolution of GP modes is obtained in the simulated scattering-type scanning near-field optical microscopy experiment, which verifies the feasibility of the reflection phase control by employing our configuration. This work not only paves a way for in-plane plasmon control but also could serve as a valuable reference to various graphene-based plasmonic applications.