▎ 摘　　要

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-Perot (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 2 pi, 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.& nbsp;(c) 2022 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).