Electric directional steering of cathodoluminescence from graphene-based hydrid nanostructures

TL;DR

This paper demonstrates that the emission direction of cathodoluminescence from graphene-nanoparticle composites can be electrically controlled to continuously span the full circle by tuning the graphene Fermi energy, enabling reconfigurable nanophotonic sources.

Contribution

It introduces a novel method to electrically steer the emission direction of cathodoluminescence using graphene plasmonic resonances and electron-beam interactions, with full 360-degree tunability.

Findings

Emission directionality can be continuously tuned by small Fermi energy variations.

Interference between electron transition radiation and nanoparticle diffraction governs beaming.

The method enables ultrafast reconfigurable radiation patterns.

Abstract

Controlling directional emission of nanophotonic radiation sources is fundamental to tailor radiation-matter interaction and to conceive highly efficient nanophotonic devices for on-chip wireless communication and information processing. Nanoantennas coupled to quantum emitters have proven to be very efficient radiation routers, while electrical control of unidirectional emission has been achieved through inelastic tunneling of electrons. Here we prove that the radiation emitted from the interaction of a high-energy electron beam with a graphene-nanoparticle composite has beaming directions which can be made to continuously span the full circle even through small variations of the graphene Fermi energy. Emission directionality stems from the interference between the double cone shaped electron transition radiation and the nanoparticle dipolar diffraction radiation. Tunability is enabled since the interference is ruled by the nanoparticle dipole moment whose amplitude and phase are driven by the hybrid plasmonic resonances of the composite and the absolute phase of the graphene plasmonic polariton launched by the electron, respectively. The flexibility of our method provides a way to exploit graphene plasmon physics to conceive improved nanosources with ultrafast reconfigurable radiation patterns.