RESUMO
A kind of graphene-based perfect absorber which can generate low-threshold and high-extinction-ratio optical bistability in the near-IR band is proposed and simulated with numerical methods. The interaction between input light and monolayer graphene in the absorber can be greatly enhanced due to the perfect absorption. The large nonlinear coefficient of graphene and the strong light-graphene interaction contribute to the nonlinear response of the structure, leading to relatively low switching thresholds of less than 2.5 MW/cm2 for an absorber with a Q factor lower than 1000. Meanwhile, the extinction ratio of bistable states in the absorber reaches an ultrahigh value of 47.3 dB at 1545.3 nm. Moreover, the influence of changing the structural parameters on the bistable behaviors is discussed in detail, showing that the structure can tolerate structural parametric deviation to some extent. The proposed bistable structure with ultra-compact size, low thresholds, high extinction ratio, and ultrafast response time could be of great applications for fabricating high-performance all-optical-communication devices.
RESUMO
A very attractive advantage of graphene is that its Fermi level can be regulated by electrostatic bias doping. It is of great significance to investigate and control the spatial location of graphene emission for graphene thermal emitters, in addition to tuning the emission intensity and emission spectrum. Here, we present a detailed theoretical model to describe the graphene emission characteristics versus gate voltages. The experimentally observed movement of the emission spot and temperature distribution of graphene emitters are basically in agreement with those from the theoretical model. Our results provide a simple method to predict the behavior of graphene emitters that is beneficial for achieving the spatial dynamic regulation of graphene infrared emission arrays.
