Photonic and plasmonic transition radiation from graphene

We theoretically study the transition radiation in the framework of full Maxwell equations, when a swift electron crosses a monolayer graphene. Based on the Sommerfeld integration, we demonstrate in the frequency domain the spatial distribution of this free-electron radiation, which clearly shows the broadband excitation of both photons and graphene plasmons. Moreover, the radiation spectra for photons and graphene plasmons are analytically derived. We find that the excitation of photons and graphene plasmons favors different particle velocities. To be specific, a higher particle velocity gives rise to the excitation of photons with better directivity and higher intensity, while a lower particle velocity enables the efficient excitation of graphene plasmons in a broader frequency range. Our work indicates that the interaction between swift charged particles and various 2D materials or van der Waals heterostructures is promising for the design of terahertz on-chip radiation sources.

Automated summary

This study theoretically investigates the transition radiation of swift electrons crossing a monolayer graphene using full Maxwell equations. The excitation of photons and graphene plasmons is found to favor different particle velocities, with higher velocities leading to better directivity and intensity for photons, and lower velocities enabling efficient excitation of graphene plasmons across a wider frequency range. The interaction between swift charged particles and 2D materials or van der Waals heterostructures shows promise for the design of terahertz on-chip radiation sources.