Dynamically tunable extraordinary light absorption in monolayer graphene

The high carrier mobility of graphene makes it an attractive material for electronics, however, graphene's application for optoelectronic systems is limited due to its low optical absorption. We present a cavity-coupled nanopatterned graphene absorber designed to sustain temporal and spatial overlap between localized surface plasmon resonance and cavity modes, thereby resulting in enhanced absorption up to an unprecedented value of theoretically $(60%)$ and experimentally measured $(45%)$ monolayer graphene in the technologically relevant 8--12-\ensuremath{\mu}m atmospheric transparent infrared imaging band. We demonstrate a wide electrostatic tunability of the absorption band $(\ensuremath{\sim}2\phantom{\rule{0.16em}{0ex}}\ensuremath{\mu}\mathrm{m})$ by modifying the Fermi energy. The proposed device design allows enhanced absorption and dynamic tunability of chemical vapor deposition grown low carrier mobility graphene which provides a significant advantage over previous strategies where absorption enhancement was limited to exfoliated high carrier mobility graphene. We developed an analytical model that incorporates the coupling of the graphene electron and substrate phonons, providing valuable and instructive insights into the modified plasmon-phonon dispersion relation necessary to interpret the experimental observations. Such gate voltage and cavity tunable enhanced absorption in chemical vapor deposited large area monolayer graphene paves the path towards the scalable development of ultrasensitive infrared photodetectors, modulators, and other optoelectronic devices.