Low-power bistability in graphene-comprising 3D photonic resonant circuits

Abstract

Practical graphene-comprising resonant structures are proposed for high-quality Kerr-induced bistability with a low input power. Two structures are designed for operation in the far-infrared (FIR) and near-infrared (NIR) frequency regimes, respectively. The nonlinear response is studied by utilizing a theoretical framework combining perturbation theory and coupled-mode theory, capable of accurately and efficiently modeling resonant structures with dispersive bulk and sheet materials. The FIR system is based on a side-coupled graphene-nanoribbon ring resonator, formed by applying a bias voltage between a uniform graphene sheet and an uneven silicon substrate. By optimizing the system geometry, we demonstrate bistable response with a theoretically infinite extinction ratio between states and an operating power of only 400 μW at 10 THz. In the NIR circuit, a silicon photonic ring resonator is overlaid with a graphene sheet. The silicon-slot geometry is judiciously chosen to maximize the field overlap with graphene, resulting in low power requirements of 90 mW at 1.55 μm. In both cases, nonlinearity stems from the instantaneous Kerr effect in graphene, allowing for ultra-fast response. Combining low input power and fast response times, the proposed components highlight the potential of graphene for nonlinear applications over a broad spectral range.