Graphene-on-plasmonic slot waveguide photodetector

Integrated silicon-based plasmonic photodetectors have attracted more and more attention recently, due to their potential applications in THz bandwidth. In this paper, by utilizing a simplified two-step lithography process, the photoconductive detector is fabricated with the core structure of plasmonic slot waveguide in two symmetric metallic slabs as microwave electrodes to integrate with mechanically exfoliated graphene. The 3-dB bandwidth of the graphene-on-plasmonic slot waveguide photodetector is exceeded 120 GHz under the theoretical calculation, and the measured bandwidth is still beyond 70 GHz due to the lack of larger-bandwidth equipment. High-speed data reception is demonstrated for 72 Gbit/s NRZ and 64 Gbit/s PAM-4 signals with a BER below 15% soft-decision FEC threshold. Based on the enhanced interactions of light and graphene induced by the subwavelength confinement from the plasmonic structure, the responsivity of 0.13 A/W is achieved under the condition of the 7-μm long detection zone and the 0.4-V bias voltage. With the advantages of ultra-compact, high-speed, large-bandwidth and compatible with the CMOS process, our photodetector has the potential to be used in high-speed optical interconnection, terahertz transmission and terahertz communication.