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

Xiaojie Jiang,Mengxin Ren,Jingjun Xu,Wei Cai,Yinxiao Xiang,Ni Zhang,Weiwei Luo,Yao Lu,Lei Wang,Jiang Fan,Zenghong Ma,Xinzheng Zhang

doi:10.1063/5.0081395

Abstract

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.

Highlights

Graphene plasmons (GPs) exhibit various remarkable properties,1–4 including strong spatial confinement and agile electrical tunability, which make them attractive to a wide range of applications.5–8 Practical applications of graphene-based plasmonic devices, such as reflectors, wavefront modulators, and phase retarders, require effective control over the graphene plasmons (GPs) propagation
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
We demonstrate that the reflection phase of GPs can be effectively controlled by electronic boundary design

Summary

INTRODUCTION

Graphene plasmons (GPs) exhibit various remarkable properties, including strong spatial confinement and agile electrical tunability, which make them attractive to a wide range of applications. Practical applications of graphene-based plasmonic devices, such as reflectors, wavefront modulators, and phase retarders, require effective control over the GP propagation. A Fabry–Pérot (F–P) cavity is constructed by two electronic boundaries and acts as an equivalent reflection boundary Based on this configuration, the reflection phase is promising to be controlled by changing the parameters of the F–P cavity. Theoretical calculations are performed, and the results show that the reflection phase could continuously vary in a wide range, almost 2π, by changing the graphene Fermi energy and the width of the F–P cavity. By investigating the evolution of GP modes in simulated scattering-type scanning near-field optical microscopy (s-SNOM) experiment, the feasibility of the reflection phase control by employing our configuration is verified. Our work provides another effective method for in-plane GP control at the nanoscale

MODEL AND METHOD

Theoretical investigation of the reflection phase control

Simulated experimental verification of the reflection phase control