Using Bottom-Up Lithography and Optical Nonlocality to Create Short-Wave Infrared Plasmonic Resonances in Graphene

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 the dramatic enhancement of light–matter interactions. In this work, we demonstrate that the characteristic scaling laws of resonant graphene plasmons change for smaller (<40 nm) plasmonic wavelengths and that those changes modify the optical confinement properties of graphene plasmonic resonators, allowing their operational frequency to be expanded into the short-wave infrared (SWIR). These effects are realized in centimeter-scale arrays of graphene resonators as narrow as 12 nm, which are created using a novel, bottom-up block copolymer lithography method. Measurements of these structures reveal that their plasmonic resonances are strongly influenced by nonlocal and quantum effects, which push their resonant frequency well into the SWIR (free-space wavelength ∼2.2 μm), 75% higher frequency than previous experimental works. The confinement factors of these resonators reach 137 ± 25, among the largest reported in literature for any type of 2D optical resonator. The combined SWIR response and large confinement of these structures make them an attractive platform to explore ultrastrongly enhanced spontaneous emission.