Scalable near-infrared graphene plasmonic resonators exhibiting strong non-local and electron quantization effects

TL;DR

This paper demonstrates the creation of ultra-narrow graphene plasmonic resonators that operate in the near-infrared range, revealing quantum effects and achieving high optical confinement, advancing the potential for enhanced light-matter interactions.

Contribution

It introduces a novel bottom-up lithography method to produce sub-12 nm graphene resonators with strong non-local and quantum effects, extending plasmonic operation into the near-infrared.

Findings

Resonant frequencies reach 2.2 μm, nearly double previous work.

Confinement factors up to 137, among the highest reported.

Quantum effects significantly influence plasmonic behavior at small scales.

Abstract

Graphene plasmonic resonators have been broadly studied in the terahertz and mid-infrared ranges because of their electrical tunability and large confinement factors which can enable dramatic enhancement of light-matter coupling. In this work, we demonstrate that the characteristic scaling laws of graphene plasmons change for smaller (< 40 nm) plasmonic wavelengths, expanding the operational frequencies of graphene plasmonic resonators into the near-infrared (NIR) and modifying their optical confinement properties. We utilize a novel bottom-up block copolymer lithography method that substantially improves upon top-down methods to create resonators as narrow as 12 nm over centimeter-scale areas. Measurements of these structures reveal that their plasmonic resonances are strongly influenced by non-local and quantum effects, which push their resonant frequency into the NIR (2.2 um), almost double the frequency of previous experimental works. The confinement factors of these resonators, meanwhile, reach 137 +/- 25, amongst the largest reported in literature for an optical cavity. While our findings indicate that the enhancement of some 'forbidden' transitions are an order of magnitude weaker than predicted, the combined NIR response and large confinement of these structures make them an attractive platform to explore ultra-strongly enhanced spontaneous emission.