On-chip graphene optoelectronic devices

There has been increasing interest in developing optoelectronic devices based on graphene, whose tunable optical and electronic properties make it applicable for both high-speed and broadband modulators and photodetectors. The flexibility and robustness of graphene make it compatible with the geometries of various devices. In this chapter, we describe chip-integrated graphene optoelectronics with nanophotonic cavities and waveguides. By depositing graphene onto photonic crystal nanocavities, it is possible to reach near-unity absorption into graphene. The graphene-photonic crystal cavity system enables a high-contrast electro-optic modulation by electrically tuning the Fermi level of graphene. In addition, high-speed operation is possible by using capacitive gating, such as through a double-layer graphene stack. The cavity also enables dramatically enhanced and spectrally selective photodetection on graphene. A similar scheme of graphene integration on nanophotonic waveguides greatly increases the interaction time of graphene with light and enables efficient, broadband, and high-speed photodetectors. Such graphene photodetectors are compatible with photonic integrated circuits and promise an alternative to traditional on-chip photodetectors. Thus, the combination of graphene optoelectronic devices with photonic chips promises a new route for ultrafast and broadband on-chip optical interconnects.