High-responsivity graphene photodetectors integrated on silicon microring resonators

Abstract

Graphene integrated photonics provides several advantages over conventional Si photonics. Single layer graphene (SLG) enables fast, broadband, and energy-efficient electro-optic modulators, optical switches and photodetectors (GPDs), and is compatible with any optical waveguide. The last major barrier to SLG-based optical receivers lies in the low responsivity -electrical output per optical input -of GPDs compared to conventional PDs. Here we overcome this shortfall by integrating a photothermoelectric GPD with a Si microring resonator. Under critical coupling, we achieve >90% light absorption in a ∼6 µm SLG channel along the Si waveguide. Exploiting the cavity-enhanced lightmatter interaction, causing carriers in SLG to reach ∼400 K for an input power of ∼0.6 mW, we get a voltage responsivity ∼90 V/W, demonstrating the feasibility of our approach. Our device is capable of detecting data rates up to 20 Gbit/s, with a receiver sensitivity enabling it to operate at a 10 −9 bit-error rate, on par with mature semiconductor technology. The natural generation of a voltage rather than a current, removes the need for transimpedance amplification, with a reduction of the energy-per-bit cost and foot-print, when compared to a traditional semiconductor-based receiver.