Controlled light-matter interaction in graphene electrooptic devices using nanophotonic cavities and waveguides

Nanophotonic devices, such as waveguides and cavities, can strongly enhance the interaction of light with graphene. We describe techniques for enhancing the interaction of photons with graphene using chip-integrated nanophotonic devices. Transferring single-layer graphene onto planar photonic crystal nanocavities enables a spectrally selective, order-of-magnitude enhancement of optical coupling with graphene, as shown by spectroscopic studies of cavity modes in visible and infrared spectral ranges. We observed dramatically cavity-enhanced absorption, hot photoluminescence emission, and Raman scattering of the monolayer graphene. We also described a broad-spectrum enhancement of the light-matter interaction by coupling graphene with a bus waveguide on a silicon-on-insulator photonic integrated circuit, which enables a 6.2-dB transmission attenuation due to the graphene absorption over a waveguide length of 70 $\mu$m. By electrically gating the graphene monolayer coupled with a planar photonic crystal nanocavity, electrooptic modulation of the cavity reflection was possible with a contrast in excess of 10 dB. Moreover, a novel modulator device based on the cavity-coupled graphene-boron nitride-graphene capacitor was fabricated, showing a modulation speed up to 0.57 GHz. These results indicate the applications of graphene-cavity devices in high-speed and high-contrast modulators with low energy consumption. The integration of graphene with nanophotonic architectures promises a new generation of compact, energy-efficient, and ultrafast electrooptic graphene devices for on-chip optical communications.