Plasmonic resonance absorption spectra in mid-infrared in an array of graphene nanoresonators

We experimentally demonstrated graphene plasmon resonant absorption in mid-IR by utilizing an array of graphene nanoribbon resonators on SiO2 substrate. By tuning resonator width we probed the graphene plasmons with λ p ≤ λ0/100 and plasmon resonances as high as 0.240 eV (2100 cm -1 ) for 40 nm wide nanoresonators. Resonant absorption spectra revealed plasmon dispersion as well as plasmon damping due to the interaction of graphene plasmons with the surface polar phonons in SiO 2 substrate and intrinsic graphene optical phonons. Graphene nanoribbons with varying widths enabled us to identify the damping mechanisms of graphene plasmons and much reduced damping was observed when the plasmon resonance frequencies were close to the substrate polar phonon frequencies. Then, by direct ebeam exposure of graphene nanoresonators, we effectively changed the carrier density and caused red-shift of the plasmon spectra. This work will provide insight into light-sensitive, frequency-tunable photodetectors based on graphene’s plasmonic excitations.