Large-Area Arrays of Short-Wave-Infrared Graphene Plasmonic Resonators Exhibiting Strong Non-Local and Electron Quantization Effects

Abstract

Abstract Body: Graphene plasmonic resonances have been broadly studied in the terahertz and mid-infrared (MIR) ranges because of their electrical tunability and large confinement factors, which can enable dramatic enhancement of light-matter interactions, among other optoelectrical applications. Plasmonic resonances occur in graphene when it is patterned into nanostructures (e.g. ribbons) which confine the graphene plasmons and enables coupling to free-space radiation. For nanostructures with dimensions greater than 15 nanometers, the characteristic scaling laws of the graphene plasmons are well approximated by the local model of graphene’s conductivity. However, we experimentally demonstrate that those scaling laws change for structures smaller than 15 nanometers due to non-local and quantum effects in the graphene. Those changes blue-shift the frequencies of the graphene plasmons, pushing their operational range from the MIR into the short-wave-infrared (SWIR). We realize these effects in centimeter-scale arrays of graphene nanoribbons as narrow as 12 nanometers that are created using a novel, bottom-up block copolymer lithography method. The devices we create exhibit tunable plasmonic resonances at wavelength as short as 2.2 μm, almost double the energy of the previous experimental works. Furthermore, the confinement factors of our resonators reach 137 ± 25, which is amongst the largest reported in literature for any type of 2D optical resonator. The combined SWIR response and large confinement factors coupled to a scalable and efficient fabrication method makes these graphene nanostructures an attractive platform to explore next-generation optoelectrical devices and strongly enhanced spontaneous emission in the SWIR.