Ultra-efficient DC-gated all-optical graphene switch

Abstract The ultrafast response and broadband absorption of all-optical graphene switches are highly desirable features for on-chip photonic switching. However, because graphene is an atomically thin material, its absorption of guided optical modes is relatively low, resulting in high saturation thresholds and switching energies for these devices. To boost the absorption of graphene, we present a practical design of an electrically-biased all-optical graphene switch that is integrated into silicon slot waveguides, which strongly confine the optical mode in the slotted region and enhance its interaction with graphene. Moreover, the design incorporates a silicon slab layer and a hafnia dielectric layer to electrically tune the saturation threshold and the switching energy of the device by applying direct-current voltages of < 0.5 V. Using this device, a high extinction ratio of 10.3 dB, a low insertion loss of < 0.7 dB, and an ultra-efficient switching energy of 79 fJ/bit at 0.23 V bias are attainable for a 40 µ m long switch. The reported performance metrics for this device are highly promising and are expected to serve the needs of next-generation photonic computing systems.