Wide Angle Electronically Tunable Enhanced Light Absorption in Nanopatterned Graphene*

Plasmonics in Dirac systems like graphene shows interesting characteristics because of massless electrons around the Dirac cone. Exciting surface plasmons on graphene is a distinct technique to increase the light absorption with low damping rate and provides the opportunity of electrical tunability of the resonance frequency and high degree of electric field confinement. Here, we demonstrate a novel design of an optical cavity-coupled hexagonal array of nanohole and nanodisk in monolayer CVD-grown graphene to excite Dirac plasmon. We study the surface plasmon lifetimes of the nanopatterns and their role in the enhanced light-matter interaction. By exploiting a high-k gate dielectric to dope the nanopatterned graphene electrostatically, the light absorption enhances to the record values of 60% on nanohole and 90% on nanodisk arrays in the 8-12 mm bandwidth with high spectral tunability. We theoretically and experimentally demonstrate, for the first time, the angular dependency of s- and p- polarized light absorption in nanopatterned graphene. The wide-angle electronically tunable extraordinary light absorption promises graphene-based optoelectronic devices.