Enhanced Asymmetric Light-Plasmon Coupling in Graphene Nanoribbons for High-Efficiency Transmissive Infrared Modulation

Abstract

Graphene plasmonic modulators can manipulate the mid-infrared light in transmission mode, which is currently challenging for traditional liquid crystal and digital micromirror devices, opening up a new avenue for infrared scene projection, infrared optical communication, and hyper spectra imaging. Nevertheless, their efficiencies are not high enough due to the single-layer atomic thickness and low free carrier density of graphene. Here, it is demonstrated that the modulation efficiency can be significantly improved by enhancing the asymmetric light-plasmon coupling. A general theoretical model is established to describe the modulation behaviors of the modulator, revealing the critical role of the asymmetric coupling rate. By using dielectric environment engineering and graphene structure design experimentally to enhance the asymmetric coupling rate from 0.45×1012 to 7.05×1012 s−1, the modulation efficiency has been improved from 4% to 41% at 1530 cm−1, while maintaining the bandwidth as large as 230 cm−1. The modulator outperforms previous transmission-type graphene plasmonic modulators in both efficiency and bandwidth, presenting great potential in next-generation infrared integrated photonics platforms.