Enhancing light-matter interaction by exciting Dirac plasmons on nanopatterned monolayer graphene is an efficient route to achieve high infrared absorption. Here, we designed and fabricated hexagonal planar arrays of nanoholes and nanodisks with and without optical cavity to excite Dirac plasmons on patterned graphene and investigate the role of plasmon lifetime, extinction cross-section, incident light polarization, angle of incident light, and pattern dimensions on the light-absorption spectra. By incorporating a high-k Al2O3 layer as the gate dielectric for dynamic electrostatic tuning of the Fermi level, we demonstrate peak absorptions of 60% and 90% for the nanohole and nanodisk patterns, respectively, in the atmospheric transparent 8-12 μm infrared imaging band with high spectral tunability. Finally, we theoretically and experimentally demonstrate angular dependence of both s- and p-polarized light absorption in monolayer graphene. Our results showcase the practical usability of low carrier mobility CVD-grown graphene for wide angle infrared absorption, which is suitable for next-generation optoelectronic devices such as photodetectors, optical switches, modulators, etc.
Keywords: electrostatic tunability; graphene; light-matter interaction; localized Dirac plasmon; mid-infrared spectral domain; optical cavity; plasmon lifetime.