Relaxing graphene plasmon excitation constraints through the use of an epsilon-near-zero substrate

TL;DR

This paper proposes using an epsilon-near-zero substrate, specifically silicon carbide, to significantly relax the constraints on graphene plasmon excitation, enabling longer wavelengths and propagation lengths.

Contribution

It introduces a theoretical method utilizing SiC substrate to enhance graphene plasmon properties by hybridizing with phonon polaritons, reducing the need for complex coupling setups.

Findings

Longer polariton wavelengths with SiC substrate

Increased propagation lengths of graphene plasmons

Hybridization with substrate phonon polaritons

Abstract

Graphene plasmons have attracted significant attention due to their tunability, potentially long propagation lengths and ultracompact wavelengths. However, the latter characteristic imposes challenges to light-plasmon coupling in practical applications, generally requiring sophisticated coupling setups, extremely high doping levels and/or graphene nanostructuting close to the resolution limit of current lithography techniques. Here, we propose and theoretically demonstrate a method for alleviating such a technological strain through the use of a practical substrate whose low and negative dielectric function naturally enlarges the graphene polariton wavelength to more manageable levels. We consider silicon carbide (SiC), as it exhibits a dielectric function whose real part is between -1 and 0, while its imaginary part remains lower than 0.05, in the 951 to 970 cm$^{-1}$ mid-infrared spectral range. Our calculations show hybridization with the substrate's phonon polariton, resulting in a polariton wavelenth that is an order of magnitude longer than obtained with a silicon dioxide substrate, while the propagation length increases by the same amount.