Tunable electro-optic analog-to-digital converter using graphene nanoshells in photonic crystal ring resonators

In this paper, we propose a novel design of a tunable electro-optic analog-to-digital converter. The proposed structure consists of a tunable three-channel demultiplexer and an optical encoder. The first part provides sampling and quantization of the input electrical analog signal based on the applied potential to the graphene nanoshells (GNSs), while the second part converts the quantized levels into two-bit binary code. The electro-optic demultiplexer is realized using three GNS-based photonic crystal resonant cavities and can be tuned by applying different biasing of the gate voltage to the GNSs. For appropriate chemical potential values of GNS, each resonant cavity can drop the optical beam into its corresponding output port. This tunable ultrafast device supports a maximum sampling rate of up to 222 GS/s, whereas its compact footprint is about 692µm2. The proposed device opens a new window to the design and fabrication of tunable graphene-based photonic crystal circuits to develop electro-optic on-chip processing systems.