Light modulation and detection are key operations in photonic integrated circuits. Lacking a bandgap, graphene makes broadband light detection with a single material possible as it absorbs uniformly across a broad range in the visible and infrared spectrum. Graphene also displays electro-absorption and electro-refraction effects that can be used for ultrafast modulation.

Instead of relying on the expensive silicon-on-insulator wafer technology widely used in silicon photonics, Graphene Flagship researchers proposed a more convenient configuration. This consisted of a pair of single-layer graphene (SLG) layers, a capacitor consisting of an SLG-insulator-SLG stack on top of a passive waveguide. "Such an arrangement boasts several advantages compared to silicon photonic modulators," explains Neumaier. As he further states, modulator fabrication does not rely on the waveguide material or the electro-absorption and electro-refraction modulation mechanisms. In addition, replacing germanium photodetectors with SLG removes the need for the fairly costly modules of germanium epitaxy and the accompanying specialised doping processes.