Silicon microring-integrated van der Waals heterostructure modulator

Abstract

Optical modulators have been consistently improved over the last years. As a crucial component in optical interconnects and nanoscale photonic devices they have undergone astonishing performance improvements regarding bandwidth, footprint and power consumption. Nevertheless, the required performance metrics do not stop pushing existing architectures to its limits, demanding new solutions for more efficient devices.Traditionally, LiNbO3 is used for light modulation due to its relatively large electro-optic effect and easy fabrication possibility. Although it has reached a high level of maturity, direct integration with silicon systems for integrated device architectures is complicated. New device architectures are necessary to meet the technological requirements of future market demands. Recently, graphene has attracted attention for photonic devices due to its exceptional high carrier mobility, broadband tunable light absorption and durability. This thesis demonstrates how graphene can bring active functionality to passive waveguide structures, resulting in a more generic solution to designing integrated photonic components, as transferring graphene is accomplishable without the complexity of standard deposition or bonding processes. On the example of a silicon microring-integrated van der Waals heterostructure modulator, I show that indeed combining graphene photonics, or two-dimensional material photonics in general and silicon photonics sets path to a new era of photonic devices, aiming to reach demanding goals, such as higher speeds, smaller footprints and less power consumption.The device is based on a capacitor structure (van der Waals heterostructure), which is integrated onto a silicon ring resonator. The modulator shows a modulation efficiency of up to 2 dB/V, which constitutes current requirements for such device architectures.